update grammar to support #

Refactor render_layout method for serialization

.github/probots.yml

@@ -0,0 +1,2 @@
+enabled:
+  - cla

.github/workflows/liquid.yml

@@ -0,0 +1,40 @@
+name: Liquid
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        entry:
+          - { ruby: 2.5, allowed-failure: false }
+          - { ruby: 2.6, allowed-failure: false }
+          - { ruby: 2.7, allowed-failure: false }
+          - { ruby: ruby-head, allowed-failure: true }
+    name: test (${{ matrix.entry.ruby }})
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.entry.ruby }}
+      - uses: actions/cache@v1
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('Gemfile') }}
+          restore-keys: ${{ runner.os }}-gems-
+      - run: bundle install --jobs=3 --retry=3 --path=vendor/bundle
+      - run: bundle exec rake
+        continue-on-error: ${{ matrix.entry.allowed-failure }}
+  memory_profile:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.7
+      - uses: actions/cache@v1
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('Gemfile') }}
+          restore-keys: ${{ runner.os }}-gems-
+      - run: bundle install --jobs=3 --retry=3 --path=vendor/bundle
+      - run: bundle exec rake memory_profile:run

.gitignore

@@ -6,3 +6,5 @@ pkg
 .rvmrc
 .ruby-version
 Gemfile.lock
+.bundle
+.byebug_history

.rubocop.yml

@@ -0,0 +1,18 @@
+inherit_from:
+  - 'https://shopify.github.io/ruby-style-guide/rubocop.yml'
+  - .rubocop_todo.yml
+
+require: rubocop-performance
+
+Performance:
+  Enabled: true
+
+AllCops:
+  TargetRubyVersion: 2.4
+  NewCops: disable
+  Exclude:
+    - 'vendor/bundle/**/*'
+
+Naming/MethodName:
+  Exclude:
+    - 'example/server/liquid_servlet.rb'

.rubocop_todo.yml

@@ -0,0 +1,57 @@
+# This configuration was generated by
+# `rubocop --auto-gen-config`
+# on 2020-12-11 18:53:41 UTC using RuboCop version 1.6.1.
+# The point is for the user to remove these configuration records
+# one by one as the offenses are removed from the code base.
+# Note that changes in the inspected code, or installation of new
+# versions of RuboCop, may require this file to be generated again.
+
+# Offense count: 2
+# Cop supports --auto-correct.
+# Configuration parameters: EnforcedStyle.
+# SupportedStyles: runtime_error, standard_error
+Lint/InheritException:
+  Exclude:
+    - 'lib/liquid/interrupts.rb'
+
+# Offense count: 113
+# Cop supports --auto-correct.
+# Configuration parameters: AutoCorrect, AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
+# URISchemes: http, https
+Layout/LineLength:
+  Max: 260
+
+# Offense count: 8
+Lint/MissingSuper:
+  Exclude:
+    - 'lib/liquid/forloop_drop.rb'
+    - 'lib/liquid/tablerowloop_drop.rb'
+    - 'test/integration/assign_test.rb'
+    - 'test/integration/context_test.rb'
+    - 'test/integration/filter_test.rb'
+    - 'test/integration/standard_filter_test.rb'
+    - 'test/integration/tags/for_tag_test.rb'
+    - 'test/integration/tags/table_row_test.rb'
+
+# Offense count: 43
+Naming/ConstantName:
+  Exclude:
+    - 'lib/liquid.rb'
+    - 'lib/liquid/block_body.rb'
+    - 'lib/liquid/tags/assign.rb'
+    - 'lib/liquid/tags/capture.rb'
+    - 'lib/liquid/tags/case.rb'
+    - 'lib/liquid/tags/cycle.rb'
+    - 'lib/liquid/tags/for.rb'
+    - 'lib/liquid/tags/if.rb'
+    - 'lib/liquid/tags/raw.rb'
+    - 'lib/liquid/tags/table_row.rb'
+    - 'lib/liquid/variable.rb'
+    - 'performance/shopify/comment_form.rb'
+    - 'performance/shopify/paginate.rb'
+    - 'test/integration/tags/include_tag_test.rb'
+
+# Offense count: 2
+Style/ClassVars:
+  Exclude:
+    - 'lib/liquid/condition.rb'

.travis.yml

@@ -1,20 +0,0 @@
-language: ruby
-
-rvm:
-  - 2.0
-  - 2.1
-  - 2.2
-  - ruby-head
-  - jruby-head
-  - rbx-2
-
-sudo: false
-
-matrix:
-  allow_failures:
-    - rvm: jruby-head
-
-script: "rake test"
-
-notifications:
-  disable: true

CONTRIBUTING.md

@@ -4,23 +4,22 @@
 
 * Bugfixes
 * Performance improvements
-* Features which are likely to be useful to the majority of Liquid users
+* Features that are likely to be useful to the majority of Liquid users
 
 ## Things we won't merge
 
-* Code which introduces considerable performance degrations
-* Code which touches performance critical parts of Liquid and comes without benchmarks
-* Features which are not important for most people (we want to keep the core Liquid code small and tidy)
-* Features which can easily be implemented on top of Liquid (for example as a custom filter or custom filesystem)
-* Code which comes without tests
-* Code which breaks existing tests
+* Code that introduces considerable performance degrations
+* Code that touches performance-critical parts of Liquid and comes without benchmarks
+* Features that are not important for most people (we want to keep the core Liquid code small and tidy)
+* Features that can easily be implemented on top of Liquid (for example as a custom filter or custom filesystem)
+* Code that does not include tests
+* Code that breaks existing tests
 
 ## Workflow
 
 * Fork the Liquid repository
 * Create a new branch in your fork
-* If it makes sense, add tests for your code and run a performance benchmark
-* Make sure all tests pass
+* If it makes sense, add tests for your code and/or run a performance benchmark
+* Make sure all tests pass (`bundle exec rake`)
 * Create a pull request
-* In the description, ping one of [@boourns](https://github.com/boourns), [@fw42](https://github.com/fw42), [@camilo](https://github.com/camilo), [@dylanahsmith](https://github.com/dylanahsmith), or [@arthurnn](https://github.com/arthurnn) and ask for a code review.
 

Gemfile

@@ -1,9 +1,27 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
+git_source(:github) do |repo_name|
+  "https://github.com/#{repo_name}.git"
+end
 
 gemspec
-gem 'stackprof', platforms: :mri_21
+
+group :benchmark, :test do
+  gem 'benchmark-ips'
+  gem 'memory_profiler'
+  gem 'terminal-table'
+
+  install_if -> { RUBY_PLATFORM !~ /mingw|mswin|java/ && RUBY_ENGINE != 'truffleruby' } do
+    gem 'stackprof'
+  end
+end
 
 group :test do
-  gem 'spy', '0.4.1'
-  gem 'benchmark-ips'
+  gem 'rubocop', '~> 1.4', require: false
+  gem 'rubocop-performance', require: false
+
+  platform :mri, :truffleruby do
+    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'master'
+  end
 end

History.md

@@ -1,26 +1,149 @@
 # Liquid Change Log
 
-## 4.0.0 / not yet released / branch "master"
-### Changed
-* Add sort_natural filter (#554) [Martin Hanzel, arthanzel]
-* Add forloop.parentloop as a reference to the parent loop (#520) [Justin Li, pushrax]
-* Block parsing moved to BlockBody class (#458) [Dylan Thacker-Smith, dylanahsmith]
-* Add concat filter to concatenate arrays (#429) [Diogo Beato, dvbeato]
-* Ruby 1.9 support dropped (#491) [Justin Li, pushrax]
-* Liquid::Template.file_system's read_template_file method is no longer passed the context. (#441) [James Reid-Smith, sunblaze]
+## 5.0.0 / 2021-01-06
+
+### Features
+* Add new `{% render %}` tag (#1122) [Samuel Doiron]
+* Add support for `as` in `{% render %}` and `{% include %}` (#1181) [Mike Angell]
+* Add `{% liquid %}` and `{% echo %}` tags (#1086) [Justin Li]
+* Add [usage tracking](README.md#usage-tracking) [Mike Angell]
+* Add `Tag.disable_tags` for disabling tags that prepend `Tag::Disableable` at render time (#1162, #1274, #1275) [Mike Angell]
+* Support using a profiler for multiple renders (#1365, #1366) [Dylan Thacker-Smith]
+
+### Fixes
+* Fix catastrophic backtracking in `RANGES_REGEX` regular expression (#1357) [Dylan Thacker-Smith]
+* Make sure the for tag's limit and offset are integers (#1094) [David Cornu]
+* Invokable methods for enumerable reject include (#1151) [Thierry Joyal]
+* Allow `default` filter to handle `false` as value (#1144) [Mike Angell]
+* Fix render length resource limit so it doesn't multiply nested output (#1285) [Dylan Thacker-Smith]
+* Fix duplication of text in raw tags (#1304) [Peter Zhu]
+* Fix strict parsing of find variable with a name expression (#1317) [Dylan Thacker-Smith]
+* Use monotonic time to measure durations in Liquid::Profiler (#1362) [Dylan Thacker-Smith]
+
+### Breaking Changes
+* Require Ruby >= 2.5 (#1131, #1310) [Mike Angell, Dylan Thacker-Smith]
+* Remove support for taint checking (#1268) [Dylan Thacker-Smith]
+* Split Strainer class into StrainerFactory and StrainerTemplate (#1208) [Thierry Joyal]
+* Remove handling of a nil context in the Strainer class (#1218) [Thierry Joyal]
+* Handle `BlockBody#blank?` at parse time (#1287) [Dylan Thacker-Smith]
+* Pass the tag markup and tokenizer to `Document#unknown_tag` (#1290) [Dylan Thacker-Smith]
+* And several internal changes
+
+### Performance Improvements
+* Reduce allocations (#1073, #1091, #1115, #1099, #1117, #1141, #1322, #1341) [Richard Monette, Florian Weingarten, Ashwin Maroli]
+* Improve resources limits performance (#1093, #1323) [Florian Weingarten, Dylan Thacker-Smith]
+
+## 4.0.3 / 2019-03-12
 
 ### Fixed
-* Fix naming of the "context variable" when dynamically including a template (#559) [Justin Li, pushrax]
-* Gracefully accept empty strings in the date filter (#555) [Loren Hale, boobooninja]
-* Fix capturing into variables with a hyphen in the name (#505) [Florian Weingarten, fw42]
-* Fix case sensitivity regression in date standard filter (#499) [Kelley Reynolds, kreynolds]
-* Disallow filters with no variable in strict mode (#475) [Justin Li, pushrax]
-* Disallow variable names in the strict parser that are not valid in the lax parser (#463) [Justin Li, pushrax]
-* Fix BlockBody#warnings taking exponential time to compute (#486) [Justin Li, pushrax]
+* Fix break and continue tags inside included templates in loops (#1072) [Justin Li]
 
-## 3.0.2 / 2015-04-24 / branch "3-0-stable"
+## 4.0.2 / 2019-03-08
 
-* Expose VariableLookup private members (#551) [Justin Li, pushrax]
+### Changed
+* Add `where` filter (#1026) [Samuel Doiron]
+* Add `ParseTreeVisitor` to iterate the Liquid AST (#1025) [Stephen Paul Weber]
+* Improve `strip_html` performance (#1032) [printercu]
+
+### Fixed
+* Add error checking for invalid combinations of inputs to sort, sort_natural, where, uniq, map, compact filters (#1059) [Garland Zhang]
+* Validate the character encoding in url_decode (#1070) [Clayton Smith]
+
+## 4.0.1 / 2018-10-09
+
+### Changed
+* Add benchmark group in Gemfile (#855) [Jerry Liu]
+* Allow benchmarks to benchmark render by itself (#851) [Jerry Liu]
+* Avoid calling `line_number` on String node when rescuing a render error. (#860) [Dylan Thacker-Smith]
+* Avoid duck typing to detect whether to call render on a node. [Dylan Thacker-Smith]
+* Clarify spelling of `reversed` on `for` block tag (#843) [Mark Crossfield]
+* Replace recursion with loop to avoid potential stack overflow from malicious input (#891, #892) [Dylan Thacker-Smith]
+* Limit block tag nesting to 100 (#894) [Dylan Thacker-Smith]
+* Replace `assert_equal nil` with `assert_nil` (#895) [Dylan Thacker-Smith]
+* Remove Spy Gem (#896) [Dylan Thacker-Smith]
+* Add `collection_name` and `variable_name` reader to `For` block (#909)
+* Symbols render as strings (#920) [Justin Li]
+* Remove default value from Hash objects (#932) [Maxime Bedard]
+* Remove one level of nesting (#944) [Dylan Thacker-Smith]
+* Update Rubocop version (#952) [Justin Li]
+* Add `at_least` and `at_most` filters (#954, #958) [Nithin Bekal]
+* Add a regression test for a liquid-c trim mode bug (#972) [Dylan Thacker-Smith]
+* Use https rather than git protocol to fetch liquid-c [Dylan Thacker-Smith]
+* Add tests against Ruby 2.4 (#963) and 2.5 (#981)
+* Replace RegExp literals with constants (#988) [Ashwin Maroli]
+* Replace unnecessary `#each_with_index` with `#each` (#992) [Ashwin Maroli]
+* Improve the unexpected end delimiter message for block tags. (#1003) [Dylan Thacker-Smith]
+* Refactor and optimize rendering (#1005) [Christopher Aue]
+* Add installation instruction (#1006) [Ben Gift]
+* Remove Circle CI (#1010)
+* Rename deprecated `BigDecimal.new` to `BigDecimal` (#1024) [Koichi ITO]
+* Rename deprecated Rubocop name (#1027) [Justin Li]
+
+### Fixed
+* Handle `join` filter on non String joiners (#857) [Richard Monette]
+* Fix duplicate inclusion condition logic error of `Liquid::Strainer.add_filter` method (#861)
+* Fix `escape`, `url_encode`, `url_decode` not handling non-string values (#898) [Thierry Joyal]
+* Fix raise when variable is defined but nil when using `strict_variables` [Pascal Betz]
+* Fix `sort` and `sort_natural` to handle arrays with nils (#930) [Eric Chan]
+
+## 4.0.0 / 2016-12-14 / branch "4-0-stable"
+
+### Changed
+* Render an opaque internal error by default for non-Liquid::Error (#835) [Dylan Thacker-Smith]
+* Ruby 2.0 support dropped (#832) [Dylan Thacker-Smith]
+* Add to_number Drop method to allow custom drops to work with number filters (#731)
+* Add strict_variables and strict_filters options to detect undefined references (#691)
+* Improve loop performance (#681) [Florian Weingarten]
+* Rename Drop method `before_method` to `liquid_method_missing` (#661) [Thierry Joyal]
+* Add url_decode filter to invert url_encode (#645) [Larry Archer]
+* Add global_filter to apply a filter to all output (#610) [Loren Hale]
+* Add compact filter (#600) [Carson Reinke]
+* Rename deprecated "has_key?" and "has_interrupt?" methods (#593) [Florian Weingarten]
+* Include template name with line numbers in render errors (574) [Dylan Thacker-Smith]
+* Add sort_natural filter (#554) [Martin Hanzel]
+* Add forloop.parentloop as a reference to the parent loop (#520) [Justin Li]
+* Block parsing moved to BlockBody class (#458) [Dylan Thacker-Smith]
+* Add concat filter to concatenate arrays (#429) [Diogo Beato]
+* Ruby 1.9 support dropped (#491) [Justin Li]
+* Liquid::Template.file_system's read_template_file method is no longer passed the context. (#441) [James Reid-Smith]
+* Remove `liquid_methods` (See https://github.com/Shopify/liquid/pull/568 for replacement)
+* Liquid::Template.register_filter raises when the module overrides registered public methods as private or protected (#705) [Gaurav Chande]
+
+### Fixed
+
+* Fix variable names being detected as an operator when starting with contains (#788) [Michael Angell]
+* Fix include tag used with strict_variables (#828) [QuickPay]
+* Fix map filter when value is a Proc (#672) [Guillaume Malette]
+* Fix truncate filter when value is not a string (#672) [Guillaume Malette]
+* Fix behaviour of escape filter when input is nil (#665) [Tanel Jakobsoo]
+* Fix sort filter behaviour with empty array input (#652) [Marcel Cary]
+* Fix test failure under certain timezones (#631) [Dylan Thacker-Smith]
+* Fix bug in uniq filter (#595) [Florian Weingarten]
+* Fix bug when "blank" and "empty" are used as variable names (#592) [Florian Weingarten]
+* Fix condition parse order in strict mode (#569) [Justin Li]
+* Fix naming of the "context variable" when dynamically including a template (#559) [Justin Li]
+* Gracefully accept empty strings in the date filter (#555) [Loren Hale]
+* Fix capturing into variables with a hyphen in the name (#505) [Florian Weingarten]
+* Fix case sensitivity regression in date standard filter (#499) [Kelley Reynolds]
+* Disallow filters with no variable in strict mode (#475) [Justin Li]
+* Disallow variable names in the strict parser that are not valid in the lax parser (#463) [Justin Li]
+* Fix BlockBody#warnings taking exponential time to compute (#486) [Justin Li]
+
+## 3.0.5 / 2015-07-23 / branch "3-0-stable"
+
+* Fix test failure under certain timezones [Dylan Thacker-Smith]
+
+## 3.0.4 / 2015-07-17
+
+* Fix chained access to multi-dimensional hashes [Florian Weingarten]
+
+## 3.0.3 / 2015-05-28
+
+* Fix condition parse order in strict mode (#569) [Justin Li]
+
+## 3.0.2 / 2015-04-24
+
+* Expose VariableLookup private members (#551) [Justin Li]
 * Documentation fixes
 
 ## 3.0.1 / 2015-01-23
@@ -29,44 +152,52 @@
 
 ## 3.0.0 / 2014-11-12
 
-* Removed Block#end_tag. Instead, override parse with `super` followed by your code. See #446 [Dylan Thacker-Smith, dylanahsmith]
+* Removed Block#end_tag. Instead, override parse with `super` followed by your code. See #446 [Dylan Thacker-Smith]
 * Fixed condition with wrong data types (#423) [Bogdan Gusiev]
-* Add url_encode to standard filters (#421) [Derrick Reimer, djreimer]
-* Add uniq to standard filters [Florian Weingarten, fw42]
-* Add exception_handler feature (#397) and #254 [Bogdan Gusiev, bogdan and Florian Weingarten, fw42]
-* Optimize variable parsing to avoid repeated regex evaluation during template rendering #383 [Jason Hiltz-Laforge, jasonhl]
-* Optimize checking for block interrupts to reduce object allocation #380 [Jason Hiltz-Laforge, jasonhl] 
-* Properly set context rethrow_errors on render! #349 [Thierry Joyal, tjoyal]
-* Fix broken rendering of variables which are equal to false (#345) [Florian Weingarten, fw42]
-* Remove ActionView template handler [Dylan Thacker-Smith, dylanahsmith]
-* Freeze lots of string literals for new Ruby 2.1 optimization (#297) [Florian Weingarten, fw42]
-* Allow newlines in tags and variables (#324) [Dylan Thacker-Smith, dylanahsmith]
-* Tag#parse is called after initialize, which now takes options instead of tokens as the 3rd argument. See #321 [Dylan Thacker-Smith, dylanahsmith]
-* Raise `Liquid::ArgumentError` instead of `::ArgumentError` when filter has wrong number of arguments #309 [Bogdan Gusiev, bogdan]
-* Add a to_s default for liquid drops (#306) [Adam Doeler, releod]
-* Add strip, lstrip, and rstrip to standard filters [Florian Weingarten, fw42]
-* Make if, for & case tags return complete and consistent nodelists (#250) [Nick Jones, dntj]
-* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith, dylanahsmith]
-* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl, bouk]
-* Fix resource counting bug with respond_to?(:length) (#263) [Florian Weingarten, fw42]
-* Allow specifying custom patterns for template filenames (#284) [Andrei Gladkyi, agladkyi]
-* Allow drops to optimize loading a slice of elements (#282) [Tom Burns, boourns]
-* Support for passing variables to snippets in subdirs (#271) [Joost Hietbrink, joost]
-* Add a class cache to avoid runtime extend calls (#249) [James Tucker, raggi]
-* Remove some legacy Ruby 1.8 compatibility code (#276) [Florian Weingarten, fw42]
-* Add default filter to standard filters (#267) [Derrick Reimer, djreimer]
-* Add optional strict parsing and warn parsing (#235) [Tristan Hume, trishume]
+* Add url_encode to standard filters (#421) [Derrick Reimer]
+* Add uniq to standard filters [Florian Weingarten]
+* Add exception_handler feature (#397) and #254 [Bogdan Gusiev, Florian Weingarten]
+* Optimize variable parsing to avoid repeated regex evaluation during template rendering #383 [Jason Hiltz-Laforge]
+* Optimize checking for block interrupts to reduce object allocation #380 [Jason Hiltz-Laforge]
+* Properly set context rethrow_errors on render! #349 [Thierry Joyal]
+* Fix broken rendering of variables which are equal to false (#345) [Florian Weingarten]
+* Remove ActionView template handler [Dylan Thacker-Smith]
+* Freeze lots of string literals for new Ruby 2.1 optimization (#297) [Florian Weingarten]
+* Allow newlines in tags and variables (#324) [Dylan Thacker-Smith]
+* Tag#parse is called after initialize, which now takes options instead of tokens as the 3rd argument. See #321 [Dylan Thacker-Smith]
+* Raise `Liquid::ArgumentError` instead of `::ArgumentError` when filter has wrong number of arguments #309 [Bogdan Gusiev]
+* Add a to_s default for liquid drops (#306) [Adam Doeler]
+* Add strip, lstrip, and rstrip to standard filters [Florian Weingarten]
+* Make if, for & case tags return complete and consistent nodelists (#250) [Nick Jones]
+* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith]
+* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl]
+* Fix resource counting bug with respond_to?(:length) (#263) [Florian Weingarten]
+* Allow specifying custom patterns for template filenames (#284) [Andrei Gladkyi]
+* Allow drops to optimize loading a slice of elements (#282) [Tom Burns]
+* Support for passing variables to snippets in subdirs (#271) [Joost Hietbrink]
+* Add a class cache to avoid runtime extend calls (#249) [James Tucker]
+* Remove some legacy Ruby 1.8 compatibility code (#276) [Florian Weingarten]
+* Add default filter to standard filters (#267) [Derrick Reimer]
+* Add optional strict parsing and warn parsing (#235) [Tristan Hume]
 * Add I18n syntax error translation (#241) [Simon Hørup Eskildsen, Sirupsen]
-* Make sort filter work on enumerable drops (#239) [Florian Weingarten, fw42]
-* Fix clashing method names in enumerable drops (#238) [Florian Weingarten, fw42]
-* Make map filter work on enumerable drops (#233) [Florian Weingarten, fw42]
-* Improved whitespace stripping for blank blocks, related to #216 [Florian Weingarten, fw42]
+* Make sort filter work on enumerable drops (#239) [Florian Weingarten]
+* Fix clashing method names in enumerable drops (#238) [Florian Weingarten]
+* Make map filter work on enumerable drops (#233) [Florian Weingarten]
+* Improved whitespace stripping for blank blocks, related to #216 [Florian Weingarten]
 
-## 2.6.1 / 2014-01-10 / branch "2-6-stable"
+## 2.6.3 / 2015-07-23 / branch "2-6-stable"
+
+* Fix test failure under certain timezones [Dylan Thacker-Smith]
+
+## 2.6.2 / 2015-01-23
+
+* Remove duplicate hash key [Parker Moore]
+
+## 2.6.1 / 2014-01-10
 
 Security fix, cherry-picked from master (4e14a65):
-* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl, bouk]
-* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith, dylanahsmith]
+* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl]
+* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith]
 
 ## 2.6.0 / 2013-11-25
 
@@ -74,37 +205,37 @@ IMPORTANT: Liquid 2.6 is going to be the last version of Liquid which maintains
 The following releases will only be tested against Ruby 1.9 and Ruby 2.0 and are likely to break on Ruby 1.8.
 
 * Bugfix for #106: fix example servlet [gnowoel]
-* Bugfix for #97: strip_html filter supports multi-line tags [Jo Liss, joliss]
-* Bugfix for #114: strip_html filter supports style tags [James Allardice, jamesallardice]
-* Bugfix for #117: 'now' support for date filter in Ruby 1.9 [Notre Dame Webgroup, ndwebgroup]
-* Bugfix for #166: truncate filter on UTF-8 strings with Ruby 1.8 [Florian Weingarten, fw42]
-* Bugfix for #204: 'raw' parsing bug [Florian Weingarten, fw42]
-* Bugfix for #150: 'for' parsing bug [Peter Schröder, phoet]
-* Bugfix for #126: Strip CRLF in strip_newline [Peter Schröder, phoet]
-* Bugfix for #174, "can't convert Fixnum into String" for "replace" [wǒ_is神仙, jsw0528]
-* Allow a Liquid::Drop to be passed into Template#render [Daniel Huckstep, darkhelmet]
-* Resource limits [Florian Weingarten, fw42]
-* Add reverse filter [Jay Strybis, unreal]
+* Bugfix for #97: strip_html filter supports multi-line tags [Jo Liss]
+* Bugfix for #114: strip_html filter supports style tags [James Allardice]
+* Bugfix for #117: 'now' support for date filter in Ruby 1.9 [Notre Dame Webgroup]
+* Bugfix for #166: truncate filter on UTF-8 strings with Ruby 1.8 [Florian Weingarten]
+* Bugfix for #204: 'raw' parsing bug [Florian Weingarten]
+* Bugfix for #150: 'for' parsing bug [Peter Schröder]
+* Bugfix for #126: Strip CRLF in strip_newline [Peter Schröder]
+* Bugfix for #174, "can't convert Fixnum into String" for "replace" [jsw0528]
+* Allow a Liquid::Drop to be passed into Template#render [Daniel Huckstep]
+* Resource limits [Florian Weingarten]
+* Add reverse filter [Jay Strybis]
 * Add utf-8 support
-* Use array instead of Hash to keep the registered filters [Tasos Stathopoulos, astathopoulos]
-* Cache tokenized partial templates [Tom Burns, boourns]
-* Avoid warnings in Ruby 1.9.3 [Marcus Stollsteimer, stomar]
-* Better documentation for 'include' tag (closes #163) [Peter Schröder, phoet]
-* Use of BigDecimal on filters to have better precision (closes #155) [Arthur Nogueira Neves, arthurnn]
+* Use array instead of Hash to keep the registered filters [Tasos Stathopoulos]
+* Cache tokenized partial templates [Tom Burns]
+* Avoid warnings in Ruby 1.9.3 [Marcus Stollsteimer]
+* Better documentation for 'include' tag (closes #163) [Peter Schröder]
+* Use of BigDecimal on filters to have better precision (closes #155) [Arthur Nogueira Neves]
 
 ## 2.5.5 / 2014-01-10 / branch "2-5-stable"
 
 Security fix, cherry-picked from master (4e14a65):
-* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl, bouk]
-* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith, dylanahsmith]
+* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl]
+* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith]
 
 ## 2.5.4 / 2013-11-11
 
-* Fix "can't convert Fixnum into String" for "replace" (#173), [wǒ_is神仙, jsw0528]
+* Fix "can't convert Fixnum into String" for "replace" (#173), [jsw0528]
 
 ## 2.5.3 / 2013-10-09
 
-* #232, #234, #237: Fix map filter bugs [Florian Weingarten, fw42]
+* #232, #234, #237: Fix map filter bugs [Florian Weingarten]
 
 ## 2.5.2 / 2013-09-03 / deleted
 
@@ -112,7 +243,7 @@ Yanked from rubygems, as it contained too many changes that broke compatibility.
 
 ## 2.5.1 / 2013-07-24
 
-* #230: Fix security issue with map filter, Use invoke_drop in map filter [Florian Weingarten, fw42]
+* #230: Fix security issue with map filter, Use invoke_drop in map filter [Florian Weingarten]
 
 ## 2.5.0 / 2013-03-06
 

README.md

@@ -42,6 +42,8 @@ Liquid is a template engine which was written with very specific requirements:
 
 ## How to use Liquid
 
+Install Liquid by adding `gem 'liquid'` to your gemfile.
+
 Liquid supports a very simple API based around the Liquid::Template class.
 For standard use you can just pass it the content of a file and call render with a parameters hash.
 
@@ -73,3 +75,40 @@ This is useful for doing things like enabling strict mode only in the theme edit
 
 It is recommended that you enable `:strict` or `:warn` mode on new apps to stop invalid templates from being created.
 It is also recommended that you use it in the template editors of existing apps to give editors better error messages.
+
+### Undefined variables and filters
+
+By default, the renderer doesn't raise or in any other way notify you if some variables or filters are missing, i.e. not passed to the `render` method.
+You can improve this situation by passing `strict_variables: true` and/or `strict_filters: true` options to the `render` method.
+When one of these options is set to true, all errors about undefined variables and undefined filters will be stored in `errors` array of a `Liquid::Template` instance.
+Here are some examples:
+
+```ruby
+template = Liquid::Template.parse("{{x}} {{y}} {{z.a}} {{z.b}}")
+template.render({ 'x' => 1, 'z' => { 'a' => 2 } }, { strict_variables: true })
+#=> '1  2 ' # when a variable is undefined, it's rendered as nil
+template.errors
+#=> [#<Liquid::UndefinedVariable: Liquid error: undefined variable y>, #<Liquid::UndefinedVariable: Liquid error: undefined variable b>]
+```
+
+```ruby
+template = Liquid::Template.parse("{{x | filter1 | upcase}}")
+template.render({ 'x' => 'foo' }, { strict_filters: true })
+#=> '' # when at least one filter in the filter chain is undefined, a whole expression is rendered as nil
+template.errors
+#=> [#<Liquid::UndefinedFilter: Liquid error: undefined filter filter1>]
+```
+
+If you want to raise on a first exception instead of pushing all of them in `errors`, you can use `render!` method:
+
+```ruby
+template = Liquid::Template.parse("{{x}} {{y}}")
+template.render!({ 'x' => 1}, { strict_variables: true })
+#=> Liquid::UndefinedVariable: Liquid error: undefined variable y
+```
+
+### Usage tracking
+
+To help track usages of a feature or code path in production, we have released opt-in usage tracking. To enable this, we provide an empty `Liquid:: Usage.increment` method which you can customize to your needs. The feature is well suited to https://github.com/Shopify/statsd-instrument. However, the choice of implementation is up to you.
+
+Once you have enabled usage tracking, we recommend reporting any events through Github Issues that your system may be logging. It is highly likely this event has been added to consider deprecating or improving code specific to this event, so please raise any concerns.

Rakefile

@@ -1,42 +1,70 @@
+# frozen_string_literal: true
+
 require 'rake'
 require 'rake/testtask'
-$LOAD_PATH.unshift File.expand_path("../lib", __FILE__)
+$LOAD_PATH.unshift(File.expand_path("../lib", __FILE__))
 require "liquid/version"
 
-task :default => 'test'
+task(default: [:test, :rubocop])
 
-desc 'run test suite with default parser'
+desc('run test suite with default parser')
 Rake::TestTask.new(:base_test) do |t|
-  t.libs << '.' << 'lib' << 'test'
+  t.libs << 'lib' << 'test'
   t.test_files = FileList['test/{integration,unit}/**/*_test.rb']
-  t.verbose = false
+  t.verbose    = false
 end
 
-desc 'run test suite with warn error mode'
+Rake::TestTask.new(:integration_test) do |t|
+  t.libs << 'lib' << 'test'
+  t.test_files = FileList['test/integration/**/*_test.rb']
+  t.verbose    = false
+end
+
+desc('run test suite with warn error mode')
 task :warn_test do
   ENV['LIQUID_PARSER_MODE'] = 'warn'
   Rake::Task['base_test'].invoke
 end
 
-desc 'runs test suite with both strict and lax parsers'
+task :rubocop do
+  if RUBY_ENGINE == 'ruby'
+    require 'rubocop/rake_task'
+    RuboCop::RakeTask.new
+  end
+end
+
+desc('runs test suite with both strict and lax parsers')
 task :test do
   ENV['LIQUID_PARSER_MODE'] = 'lax'
   Rake::Task['base_test'].invoke
+
   ENV['LIQUID_PARSER_MODE'] = 'strict'
   Rake::Task['base_test'].reenable
   Rake::Task['base_test'].invoke
+
+  if RUBY_ENGINE == 'ruby' || RUBY_ENGINE == 'truffleruby'
+    ENV['LIQUID_C'] = '1'
+
+    ENV['LIQUID_PARSER_MODE'] = 'lax'
+    Rake::Task['integration_test'].reenable
+    Rake::Task['integration_test'].invoke
+
+    ENV['LIQUID_PARSER_MODE'] = 'strict'
+    Rake::Task['integration_test'].reenable
+    Rake::Task['integration_test'].invoke
+  end
 end
 
-task :gem => :build
+task(gem: :build)
 task :build do
   system "gem build liquid.gemspec"
 end
 
-task :install => :build do
+task install: :build do
   system "gem install liquid-#{Liquid::VERSION}.gem"
 end
 
-task :release => :build do
+task release: :build do
   system "git tag -a v#{Liquid::VERSION} -m 'Tagging #{Liquid::VERSION}'"
   system "git push --tags"
   system "gem push liquid-#{Liquid::VERSION}.gem"
@@ -44,7 +72,6 @@ task :release => :build do
 end
 
 namespace :benchmark do
-
   desc "Run the liquid benchmark with lax parsing"
   task :run do
     ruby "./performance/benchmark.rb lax"
@@ -56,9 +83,7 @@ namespace :benchmark do
   end
 end
 
-
 namespace :profile do
-
   desc "Run the liquid profile/performance coverage"
   task :run do
     ruby "./performance/profile.rb"
@@ -68,10 +93,20 @@ namespace :profile do
   task :strict do
     ruby "./performance/profile.rb strict"
   end
-
 end
 
-desc "Run example"
+namespace :memory_profile do
+  desc "Run memory profiler"
+  task :run do
+    ruby "./performance/memory_profile.rb"
+  end
+end
+
+desc("Run example")
 task :example do
   ruby "-w -d -Ilib example/server/server.rb"
 end
+
+task :console do
+  exec 'irb -I lib -r liquid'
+end

example/server/example_servlet.rb

@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 module ProductsFilter
   def price(integer)
-    sprintf("$%.2d USD", integer / 100.0)
+    format("$%.2d USD", integer / 100.0)
   end
 
   def prettyprint(text)
-    text.gsub( /\*(.*)\*/, '<b>\1</b>' )
+    text.gsub(/\*(.*)\*/, '<b>\1</b>')
   end
 
   def count(array)
@@ -17,30 +19,28 @@ module ProductsFilter
 end
 
 class Servlet < LiquidServlet
-
   def index
     { 'date' => Time.now }
   end
 
   def products
-    { 'products' => products_list, 'more_products' => more_products_list, 'description' => description, 'section' => 'Snowboards', 'cool_products' => true}
+    { 'products' => products_list, 'more_products' => more_products_list, 'description' => description, 'section' => 'Snowboards', 'cool_products' => true }
   end
 
   private
 
   def products_list
-    [{'name' => 'Arbor Draft', 'price' => 39900, 'description' => 'the *arbor draft* is a excellent product' },
-    {'name' => 'Arbor Element', 'price' => 40000, 'description' => 'the *arbor element* rocks for freestyling'},
-    {'name' => 'Arbor Diamond', 'price' => 59900, 'description' => 'the *arbor diamond* is a made up product because im obsessed with arbor and have no creativity'}]
+    [{ 'name' => 'Arbor Draft', 'price' => 39900, 'description' => 'the *arbor draft* is a excellent product' },
+     { 'name' => 'Arbor Element', 'price' => 40000, 'description' => 'the *arbor element* rocks for freestyling' },
+     { 'name' => 'Arbor Diamond', 'price' => 59900, 'description' => 'the *arbor diamond* is a made up product because im obsessed with arbor and have no creativity' }]
   end
 
   def more_products_list
-    [{'name' => 'Arbor Catalyst', 'price' => 39900, 'description' => 'the *arbor catalyst* is an advanced drop-through for freestyle and flatground performance and versatility' },
-    {'name' => 'Arbor Fish', 'price' => 40000, 'description' => 'the *arbor fish* is a compact pin that features an extended wheelbase and time-honored teardrop shape'}]
+    [{ 'name' => 'Arbor Catalyst', 'price' => 39900, 'description' => 'the *arbor catalyst* is an advanced drop-through for freestyle and flatground performance and versatility' },
+     { 'name' => 'Arbor Fish', 'price' => 40000, 'description' => 'the *arbor fish* is a compact pin that features an extended wheelbase and time-honored teardrop shape' }]
   end
 
   def description
     "List of Products ~ This is a list of products with price and description."
   end
-
 end

example/server/liquid_servlet.rb

@@ -1,5 +1,6 @@
-class LiquidServlet < WEBrick::HTTPServlet::AbstractServlet
+# frozen_string_literal: true
 
+class LiquidServlet < WEBrick::HTTPServlet::AbstractServlet
   def do_GET(req, res)
     handle(:get, req, res)
   end
@@ -10,20 +11,20 @@ class LiquidServlet < WEBrick::HTTPServlet::AbstractServlet
 
   private
 
-  def handle(type, req, res)
-    @request = req
+  def handle(_type, req, res)
+    @request  = req
     @response = res
 
     @request.path_info =~ /(\w+)\z/
-    @action = $1 || 'index'
+    @action  = Regexp.last_match(1) || 'index'
     @assigns = send(@action) if respond_to?(@action)
 
     @response['Content-Type'] = "text/html"
     @response.status = 200
-    @response.body = Liquid::Template.parse(read_template).render(@assigns, :filters => [ProductsFilter])
+    @response.body   = Liquid::Template.parse(read_template).render(@assigns, filters: [ProductsFilter])
   end
 
   def read_template(filename = @action)
-    File.read( File.dirname(__FILE__) + "/templates/#{filename}.liquid" )
+    File.read("#{__dir__}/templates/#{filename}.liquid")
   end
 end

example/server/server.rb

@@ -1,14 +1,14 @@
+# frozen_string_literal: true
+
 require 'webrick'
 require 'rexml/document'
 
-DIR = File.expand_path(File.dirname(__FILE__))
-
-require DIR + '/../../lib/liquid'
-require DIR + '/liquid_servlet'
-require DIR + '/example_servlet'
+require_relative '../../lib/liquid'
+require_relative 'liquid_servlet'
+require_relative 'example_servlet'
 
 # Setup webrick
-server = WEBrick::HTTPServer.new( :Port => ARGV[1] || 3000 )
+server = WEBrick::HTTPServer.new(Port: ARGV[1] || 3000)
 server.mount('/', Servlet)
-trap("INT"){ server.shutdown }
+trap("INT") { server.shutdown }
 server.start

lib/liquid.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (c) 2005 Tobias Luetke
 #
 # Permission is hereby granted, free of charge, to any person obtaining
@@ -21,9 +23,10 @@
 
 module Liquid
   FilterSeparator             = /\|/
-  ArgumentSeparator           = ','.freeze
-  FilterArgumentSeparator     = ':'.freeze
-  VariableAttributeSeparator  = '.'.freeze
+  ArgumentSeparator           = ','
+  FilterArgumentSeparator     = ':'
+  VariableAttributeSeparator  = '.'
+  WhitespaceControl           = '-'
   TagStart                    = /\{\%/
   TagEnd                      = /\%\}/
   VariableSignature           = /\(?[\w\-\.\[\]]\)?/
@@ -34,28 +37,36 @@ module Liquid
   QuotedString                = /"[^"]*"|'[^']*'/
   QuotedFragment              = /#{QuotedString}|(?:[^\s,\|'"]|#{QuotedString})+/o
   TagAttributes               = /(\w+)\s*\:\s*(#{QuotedFragment})/o
-  AnyStartingTag              = /\{\{|\{\%/
+  AnyStartingTag              = /#{TagStart}|#{VariableStart}/o
   PartialTemplateParser       = /#{TagStart}.*?#{TagEnd}|#{VariableStart}.*?#{VariableIncompleteEnd}/om
   TemplateParser              = /(#{PartialTemplateParser}|#{AnyStartingTag})/om
   VariableParser              = /\[[^\]]+\]|#{VariableSegment}+\??/o
 
+  RAISE_EXCEPTION_LAMBDA = ->(_e) { raise }
+
   singleton_class.send(:attr_accessor, :cache_classes)
   self.cache_classes = true
 end
 
 require "liquid/version"
+require 'liquid/parse_tree_visitor'
 require 'liquid/lexer'
 require 'liquid/parser'
 require 'liquid/i18n'
 require 'liquid/drop'
+require 'liquid/tablerowloop_drop'
+require 'liquid/forloop_drop'
 require 'liquid/extensions'
 require 'liquid/errors'
 require 'liquid/interrupts'
-require 'liquid/strainer'
+require 'liquid/strainer_factory'
+require 'liquid/strainer_template'
 require 'liquid/expression'
 require 'liquid/context'
 require 'liquid/parser_switching'
 require 'liquid/tag'
+require 'liquid/tag/disabler'
+require 'liquid/tag/disableable'
 require 'liquid/block'
 require 'liquid/block_body'
 require 'liquid/document'
@@ -67,10 +78,15 @@ require 'liquid/resource_limits'
 require 'liquid/template'
 require 'liquid/standardfilters'
 require 'liquid/condition'
-require 'liquid/module_ex'
 require 'liquid/utils'
-require 'liquid/token'
+require 'liquid/tokenizer'
+require 'liquid/parse_context'
+require 'liquid/partial_cache'
+require 'liquid/usage'
+require 'liquid/register'
+require 'liquid/static_registers'
+require 'liquid/template_factory'
 
 # Load all the tags of the standard library
 #
-Dir[File.dirname(__FILE__) + '/liquid/tags/*.rb'].each { |f| require f }
+Dir["#{__dir__}/liquid/tags/*.rb"].each { |f| require f }

lib/liquid/block.rb

@@ -1,16 +1,22 @@
+# frozen_string_literal: true
+
 module Liquid
   class Block < Tag
+    MAX_DEPTH = 100
+
     def initialize(tag_name, markup, options)
       super
       @blank = true
     end
 
     def parse(tokens)
-      @body = BlockBody.new
-      while more = parse_body(@body, tokens)
+      @body = new_body
+      while parse_body(@body, tokens)
       end
+      @body.freeze
     end
 
+    # For backwards compatibility
     def render(context)
       @body.render(context)
     end
@@ -23,32 +29,29 @@ module Liquid
       @body.nodelist
     end
 
-    # warnings of this block and all sub-tags
-    def warnings
-      all_warnings = []
-      all_warnings.concat(@warnings) if @warnings
-
-      (nodelist || []).each do |node|
-        all_warnings.concat(node.warnings || []) if node.respond_to?(:warnings)
-      end
-
-      all_warnings
+    def unknown_tag(tag_name, _markup, _tokenizer)
+      Block.raise_unknown_tag(tag_name, block_name, block_delimiter, parse_context)
     end
 
-    def unknown_tag(tag, params, tokens)
-      case tag
-      when 'else'.freeze
-        raise SyntaxError.new(options[:locale].t("errors.syntax.unexpected_else".freeze,
-                                                 :block_name => block_name))
-      when 'end'.freeze
-        raise SyntaxError.new(options[:locale].t("errors.syntax.invalid_delimiter".freeze,
-                                                 :block_name => block_name,
-                                                 :block_delimiter => block_delimiter))
+    # @api private
+    def self.raise_unknown_tag(tag, block_name, block_delimiter, parse_context)
+      if tag == 'else'
+        raise SyntaxError, parse_context.locale.t("errors.syntax.unexpected_else",
+          block_name: block_name)
+      elsif tag.start_with?('end')
+        raise SyntaxError, parse_context.locale.t("errors.syntax.invalid_delimiter",
+          tag: tag,
+          block_name: block_name,
+          block_delimiter: block_delimiter)
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.unknown_tag".freeze, :tag => tag))
+        raise SyntaxError, parse_context.locale.t("errors.syntax.unknown_tag", tag: tag)
       end
     end
 
+    def raise_tag_never_closed(block_name)
+      raise SyntaxError, parse_context.locale.t("errors.syntax.tag_never_closed", block_name: block_name)
+    end
+
     def block_name
       @tag_name
     end
@@ -57,24 +60,32 @@ module Liquid
       @block_delimiter ||= "end#{block_name}"
     end
 
-    def format
-      "{% #{raw} %}#{@body.format}{% #{block_delimiter} %}"
+    private
+
+    # @api public
+    def new_body
+      parse_context.new_block_body
     end
 
-    protected
-
+    # @api public
     def parse_body(body, tokens)
-      body.parse(tokens, options) do |end_tag_name, end_tag_params|
-        @blank &&= body.blank?
+      if parse_context.depth >= MAX_DEPTH
+        raise StackLevelError, "Nesting too deep"
+      end
+      parse_context.depth += 1
+      begin
+        body.parse(tokens, parse_context) do |end_tag_name, end_tag_params|
+          @blank &&= body.blank?
 
-        return false if end_tag_name == block_delimiter
-        unless end_tag_name
-          raise SyntaxError.new(@options[:locale].t("errors.syntax.tag_never_closed".freeze, :block_name => block_name))
+          return false if end_tag_name == block_delimiter
+          raise_tag_never_closed(block_name) unless end_tag_name
+
+          # this tag is not registered with the system
+          # pass it to the current block for special handling or error reporting
+          unknown_tag(end_tag_name, end_tag_params, tokens)
         end
-
-        # this tag is not registered with the system
-        # pass it to the current block for special handling or error reporting
-        unknown_tag(end_tag_name, end_tag_params, tokens)
+      ensure
+        parse_context.depth -= 1
       end
 
       true

lib/liquid/block_body.rb

@@ -1,143 +1,255 @@
+# frozen_string_literal: true
+
+require 'English'
+
 module Liquid
   class BlockBody
-    FullToken = /\A#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}\z/om
-    ContentOfVariable = /\A#{VariableStart}(.*)#{VariableEnd}\z/om
-    TAGSTART = "{%".freeze
-    VARSTART = "{{".freeze
+    LiquidTagToken      = /\A\s*([\w#]+)\s*(.*?)\z/o
+    FullToken           = /\A#{TagStart}#{WhitespaceControl}?(\s*)(\w+)(\s*)(.*?)#{WhitespaceControl}?#{TagEnd}\z/om
+    ContentOfVariable   = /\A#{VariableStart}#{WhitespaceControl}?(.*?)#{WhitespaceControl}?#{VariableEnd}\z/om
+    WhitespaceOrNothing = /\A\s*\z/
+    TAGSTART            = "{%"
+    VARSTART            = "{{"
 
     attr_reader :nodelist
 
     def initialize
       @nodelist = []
-      @blank = true
+      @blank    = true
     end
 
-    def parse(tokens, options)
-      while token = tokens.shift
-        begin
-          unless token.empty?
-            case
-            when token.start_with?(TAGSTART)
-              if token =~ FullToken
-                tag_name = $1
-                markup = $2
-                # fetch the tag from registered blocks
-                if tag = Template.tags[tag_name]
-                  markup = token.child(markup) if token.is_a?(Token)
-                  new_tag = tag.parse(tag_name, markup, tokens, options)
-                  new_tag.line_number = token.line_number if token.is_a?(Token)
-                  @blank &&= new_tag.blank?
-                  @nodelist << new_tag
-                else
-                  # end parsing if we reach an unknown tag and let the caller decide
-                  # determine how to proceed
-                  return yield tag_name, markup
-                end
-              else
-                raise_missing_tag_terminator(token, options)
-              end
-            when token.start_with?(VARSTART)
-              new_var = create_variable(token, options)
-              new_var.line_number = token.line_number if token.is_a?(Token)
-              @nodelist << new_var
-              @blank = false
-            else
-              @nodelist << token
-              @blank &&= !!(token =~ /\A\s*\z/)
-            end
+    def parse(tokenizer, parse_context, &block)
+      raise FrozenError, "can't modify frozen Liquid::BlockBody" if frozen?
+
+      parse_context.line_number = tokenizer.line_number
+
+      if tokenizer.for_liquid_tag
+        parse_for_liquid_tag(tokenizer, parse_context, &block)
+      else
+        parse_for_document(tokenizer, parse_context, &block)
+      end
+    end
+
+    def freeze
+      @nodelist.freeze
+      super
+    end
+
+    private def parse_for_liquid_tag(tokenizer, parse_context)
+      while (token = tokenizer.shift)
+        unless token.empty? || token =~ WhitespaceOrNothing
+          unless token =~ LiquidTagToken
+            # line isn't empty but didn't match tag syntax, yield and let the
+            # caller raise a syntax error
+            return yield token, token
           end
-        rescue SyntaxError => e
-          e.set_line_number_from_token(token)
-          raise
+          tag_name = Regexp.last_match(1)
+          markup   = Regexp.last_match(2)
+          unless (tag = registered_tags[tag_name])
+            # end parsing if we reach an unknown tag and let the caller decide
+            # determine how to proceed
+            return yield tag_name, markup
+          end
+          new_tag = tag.parse(tag_name, markup, tokenizer, parse_context)
+          @blank &&= new_tag.blank?
+          @nodelist << new_tag
         end
+        parse_context.line_number = tokenizer.line_number
       end
 
       yield nil, nil
     end
 
+    # @api private
+    def self.unknown_tag_in_liquid_tag(tag, parse_context)
+      Block.raise_unknown_tag(tag, 'liquid', '%}', parse_context)
+    end
+
+    # @api private
+    def self.raise_missing_tag_terminator(token, parse_context)
+      raise SyntaxError, parse_context.locale.t("errors.syntax.tag_termination", token: token, tag_end: TagEnd.inspect)
+    end
+
+    # @api private
+    def self.raise_missing_variable_terminator(token, parse_context)
+      raise SyntaxError, parse_context.locale.t("errors.syntax.variable_termination", token: token, tag_end: VariableEnd.inspect)
+    end
+
+    # @api private
+    def self.render_node(context, output, node)
+      node.render_to_output_buffer(context, output)
+    rescue => exc
+      blank_tag = !node.instance_of?(Variable) && node.blank?
+      rescue_render_node(context, output, node.line_number, exc, blank_tag)
+    end
+
+    # @api private
+    def self.rescue_render_node(context, output, line_number, exc, blank_tag)
+      case exc
+      when MemoryError
+        raise
+      when UndefinedVariable, UndefinedDropMethod, UndefinedFilter
+        context.handle_error(exc, line_number)
+      else
+        error_message = context.handle_error(exc, line_number)
+        unless blank_tag # conditional for backwards compatibility
+          output << error_message
+        end
+      end
+    end
+
+    private def parse_liquid_tag(markup, parse_context)
+      liquid_tag_tokenizer = parse_context.new_tokenizer(
+        markup, start_line_number: parse_context.line_number, for_liquid_tag: true
+      )
+      parse_for_liquid_tag(liquid_tag_tokenizer, parse_context) do |end_tag_name, _end_tag_markup|
+        if end_tag_name
+          BlockBody.unknown_tag_in_liquid_tag(end_tag_name, parse_context)
+        end
+      end
+    end
+
+    private def parse_for_document(tokenizer, parse_context)
+      while (token = tokenizer.shift)
+        next if token.empty?
+        case
+        when token.start_with?(TAGSTART)
+          whitespace_handler(token, parse_context)
+          unless token =~ FullToken
+            BlockBody.raise_missing_tag_terminator(token, parse_context)
+          end
+          tag_name = Regexp.last_match(2)
+          markup   = Regexp.last_match(4)
+
+          if parse_context.line_number
+            # newlines inside the tag should increase the line number,
+            # particularly important for multiline {% liquid %} tags
+            parse_context.line_number += Regexp.last_match(1).count("\n") + Regexp.last_match(3).count("\n")
+          end
+
+          if tag_name == 'liquid'
+            parse_liquid_tag(markup, parse_context)
+            next
+          end
+
+          unless (tag = registered_tags[tag_name])
+            # end parsing if we reach an unknown tag and let the caller decide
+            # determine how to proceed
+            return yield tag_name, markup
+          end
+          new_tag = tag.parse(tag_name, markup, tokenizer, parse_context)
+          @blank &&= new_tag.blank?
+          @nodelist << new_tag
+        when token.start_with?(VARSTART)
+          whitespace_handler(token, parse_context)
+          @nodelist << create_variable(token, parse_context)
+          @blank = false
+        else
+          if parse_context.trim_whitespace
+            token.lstrip!
+          end
+          parse_context.trim_whitespace = false
+          @nodelist << token
+          @blank &&= !!(token =~ WhitespaceOrNothing)
+        end
+        parse_context.line_number = tokenizer.line_number
+      end
+
+      yield nil, nil
+    end
+
+    def whitespace_handler(token, parse_context)
+      if token[2] == WhitespaceControl
+        previous_token = @nodelist.last
+        if previous_token.is_a?(String)
+          first_byte = previous_token.getbyte(0)
+          previous_token.rstrip!
+          if previous_token.empty? && parse_context[:bug_compatible_whitespace_trimming] && first_byte
+            previous_token << first_byte
+          end
+        end
+      end
+      parse_context.trim_whitespace = (token[-3] == WhitespaceControl)
+    end
+
     def blank?
       @blank
     end
 
-    def warnings
-      all_warnings = []
-      nodelist.each do |node|
-        all_warnings.concat(node.warnings || []) if node.respond_to?(:warnings)
-      end
-      all_warnings
+    # Remove blank strings in the block body for a control flow tag (e.g. `if`, `for`, `case`, `unless`)
+    # with a blank body.
+    #
+    # For example, in a conditional assignment like the following
+    #
+    # ```
+    # {% if size > max_size %}
+    #   {% assign size = max_size %}
+    # {% endif %}
+    # ```
+    #
+    # we assume the intention wasn't to output the blank spaces in the `if` tag's block body, so this method
+    # will remove them to reduce the render output size.
+    #
+    # Note that it is now preferred to use the `liquid` tag for this use case.
+    def remove_blank_strings
+      raise "remove_blank_strings only support being called on a blank block body" unless @blank
+      @nodelist.reject! { |node| node.instance_of?(String) }
     end
 
     def render(context)
-      output = []
-      context.resource_limits.render_score += @nodelist.length
-
-      @nodelist.each do |token|
-        # Break out if we have any unhanded interrupts.
-        break if context.has_interrupt?
-
-        begin
-          # If we get an Interrupt that means the block must stop processing. An
-          # Interrupt is any command that stops block execution such as {% break %}
-          # or {% continue %}
-          if token.is_a?(Continue) or token.is_a?(Break)
-            context.push_interrupt(token.interrupt)
-            break
-          end
-
-          token_output = render_token(token, context)
-
-          unless token.is_a?(Block) && token.blank?
-            output << token_output
-          end
-        rescue MemoryError => e
-          raise e
-        rescue ::StandardError => e
-          output << context.handle_error(e, token)
-        end
-      end
-
-      output.join
+      render_to_output_buffer(context, +'')
     end
 
-    def format
-      @nodelist.map do |node|
-        if node.is_a?(Variable)
-          "{{ #{node.format} }}"
-        elsif node.is_a?(Tag)
-          node.format
+    def render_to_output_buffer(context, output)
+      freeze unless frozen?
+
+      context.resource_limits.increment_render_score(@nodelist.length)
+
+      idx = 0
+      while (node = @nodelist[idx])
+        if node.instance_of?(String)
+          output << node
         else
-          node
+          render_node(context, output, node)
+          # If we get an Interrupt that means the block must stop processing. An
+          # Interrupt is any command that stops block execution such as {% break %}
+          # or {% continue %}. These tags may also occur through Block or Include tags.
+          break if context.interrupt? # might have happened in a for-block
         end
-      end.join
+        idx += 1
+
+        context.resource_limits.increment_write_score(output)
+      end
+
+      output
     end
 
     private
 
-    def render_token(token, context)
-      token_output = (token.respond_to?(:render) ? token.render(context) : token)
-      token_str = token_output.is_a?(Array) ? token_output.join : token_output.to_s
-
-      context.resource_limits.render_length += token_str.length
-      if context.resource_limits.reached?
-        raise MemoryError.new("Memory limits exceeded".freeze)
-      end
-      token_str
+    def render_node(context, output, node)
+      BlockBody.render_node(context, output, node)
     end
 
-    def create_variable(token, options)
+    def create_variable(token, parse_context)
       token.scan(ContentOfVariable) do |content|
-        markup = token.is_a?(Token) ? token.child(content.first) : content.first
-        return Variable.new(markup, options)
+        markup = content.first
+        return Variable.new(markup, parse_context)
       end
-      raise_missing_variable_terminator(token, options)
+      BlockBody.raise_missing_variable_terminator(token, parse_context)
     end
 
-    def raise_missing_tag_terminator(token, options)
-      raise SyntaxError.new(options[:locale].t("errors.syntax.tag_termination".freeze, :token => token, :tag_end => TagEnd.inspect))
+    # @deprecated Use {.raise_missing_tag_terminator} instead
+    def raise_missing_tag_terminator(token, parse_context)
+      BlockBody.raise_missing_tag_terminator(token, parse_context)
     end
 
-    def raise_missing_variable_terminator(token, options)
-      raise SyntaxError.new(options[:locale].t("errors.syntax.variable_termination".freeze, :token => token, :tag_end => VariableEnd.inspect))
+    # @deprecated Use {.raise_missing_variable_terminator} instead
+    def raise_missing_variable_terminator(token, parse_context)
+      BlockBody.raise_missing_variable_terminator(token, parse_context)
+    end
+
+    def registered_tags
+      Template.tags
     end
   end
 end

lib/liquid/condition.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # Container for liquid nodes which conveniently wraps decision making logic
   #
@@ -8,59 +10,83 @@ module Liquid
   #
   class Condition #:nodoc:
     @@operators = {
-      '=='.freeze => lambda { |cond, left, right|  cond.send(:equal_variables, left, right) },
-      '!='.freeze => lambda { |cond, left, right| !cond.send(:equal_variables, left, right) },
-      '<>'.freeze => lambda { |cond, left, right| !cond.send(:equal_variables, left, right) },
-      '<'.freeze  => :<,
-      '>'.freeze  => :>,
-      '>='.freeze => :>=,
-      '<='.freeze => :<=,
-      'contains'.freeze => lambda { |cond, left, right|
-        left && right && left.respond_to?(:include?) ? left.include?(right) : false
-      }
+      '==' => ->(cond, left, right) {  cond.send(:equal_variables, left, right) },
+      '!=' => ->(cond, left, right) { !cond.send(:equal_variables, left, right) },
+      '<>' => ->(cond, left, right) { !cond.send(:equal_variables, left, right) },
+      '<' => :<,
+      '>' => :>,
+      '>=' => :>=,
+      '<=' => :<=,
+      'contains' => lambda do |_cond, left, right|
+        if left && right && left.respond_to?(:include?)
+          right = right.to_s if left.is_a?(String)
+          left.include?(right)
+        else
+          false
+        end
+      end,
+    }
+
+    class MethodLiteral
+      attr_reader :method_name, :to_s
+
+      def initialize(method_name, to_s)
+        @method_name = method_name
+        @to_s = to_s
+      end
+    end
+
+    @@method_literals = {
+      'blank' => MethodLiteral.new(:blank?, '').freeze,
+      'empty' => MethodLiteral.new(:empty?, '').freeze,
     }
 
     def self.operators
       @@operators
     end
 
-    attr_reader :attachment
+    def self.parse_expression(parse_context, markup)
+      @@method_literals[markup] || parse_context.parse_expression(markup)
+    end
+
+    attr_reader :attachment, :child_condition
     attr_accessor :left, :operator, :right
 
     def initialize(left = nil, operator = nil, right = nil)
-      @left = left
+      @left     = left
       @operator = operator
-      @right = right
+      @right    = right
+
       @child_relation  = nil
       @child_condition = nil
-
-      if right && right.is_a?(VariableLookup) && right.name.nil?
-        # Strip blank variable lookups resulting from cases like:
-        # {% if foo && bar %}
-        @right = nil
-      end
     end
 
     def evaluate(context = Context.new)
-      result = interpret_condition(left, right, operator, context)
+      condition = self
+      result = nil
+      loop do
+        result = interpret_condition(condition.left, condition.right, condition.operator, context)
 
-      case @child_relation
-      when :or
-        result || @child_condition.evaluate(context)
-      when :and
-        result && @child_condition.evaluate(context)
-      else
-        result
+        case condition.child_relation
+        when :or
+          break if result
+        when :and
+          break unless result
+        else
+          break
+        end
+        condition = condition.child_condition
       end
+      result
     end
 
     def or(condition)
-      @child_relation = :or
+      @child_relation  = :or
       @child_condition = condition
     end
 
     def and(condition)
-      @child_relation = :and
+      @child_relation  = :and
       @child_condition = condition
     end
 
@@ -73,37 +99,27 @@ module Liquid
     end
 
     def inspect
-      "#<Condition #{[@left, @operator, @right].compact.join(' '.freeze)}>"
+      "#<Condition #{[@left, @operator, @right].compact.join(' ')}>"
     end
 
-    def format
-      out = if operator.nil?
-        Expression.format(left)
-      else
-        "#{Expression.format(left)} #{operator} #{Expression.format(right)}"
-      end
+    protected
 
-      if @child_relation
-        "#{out} #{@child_relation.to_s} #{@child_condition.format}"
-      else
-        out
-      end
-    end
+    attr_reader :child_relation
 
     private
 
     def equal_variables(left, right)
-      if left.is_a?(Symbol)
-        if right.respond_to?(left)
-          return right.send(left.to_s)
+      if left.is_a?(MethodLiteral)
+        if right.respond_to?(left.method_name)
+          return right.send(left.method_name)
         else
           return nil
         end
       end
 
-      if right.is_a?(Symbol)
-        if left.respond_to?(right)
-          return left.send(right.to_s)
+      if right.is_a?(MethodLiteral)
+        if left.respond_to?(right.method_name)
+          return left.send(right.method_name)
         else
           return nil
         end
@@ -116,36 +132,41 @@ module Liquid
       # If the operator is empty this means that the decision statement is just
       # a single variable. We can just poll this variable from the context and
       # return this as the result.
-      return context.evaluate(left) if op == nil
+      return context.evaluate(left) if op.nil?
 
-      left = context.evaluate(left)
+      left  = context.evaluate(left)
       right = context.evaluate(right)
 
-      operation = self.class.operators[op] || raise(Liquid::ArgumentError.new("Unknown operator #{op}"))
+      operation = self.class.operators[op] || raise(Liquid::ArgumentError, "Unknown operator #{op}")
 
       if operation.respond_to?(:call)
         operation.call(self, left, right)
-      elsif left.respond_to?(operation) and right.respond_to?(operation)
+      elsif left.respond_to?(operation) && right.respond_to?(operation) && !left.is_a?(Hash) && !right.is_a?(Hash)
         begin
           left.send(operation, right)
         rescue ::ArgumentError => e
-          raise Liquid::ArgumentError.new(e.message)
+          raise Liquid::ArgumentError, e.message
         end
-      else
-        nil
+      end
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.left, @node.right,
+          @node.child_condition, @node.attachment
+        ].compact
       end
     end
   end
 
-
   class ElseCondition < Condition
     def else?
       true
     end
 
-    def evaluate(context)
+    def evaluate(_context)
       true
     end
   end
-
 end

lib/liquid/context.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Context keeps the variable stack and resolves variables, as well as keywords
   #
   #   context['variable'] = 'testing'
@@ -13,29 +14,49 @@ module Liquid
   #
   #   context['bob']  #=> nil  class Context
   class Context
-    attr_reader :scopes, :errors, :registers, :environments, :resource_limits
-    attr_accessor :exception_handler
+    attr_reader :scopes, :errors, :registers, :environments, :resource_limits, :static_registers, :static_environments
+    attr_accessor :exception_renderer, :template_name, :partial, :global_filter, :strict_variables, :strict_filters
 
-    def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil)
-      @environments     = [environments].flatten
-      @scopes           = [(outer_scope || {})]
-      @registers        = registers
-      @errors           = []
-      @resource_limits  = resource_limits || ResourceLimits.new(Template.default_resource_limits)
-      squash_instance_assigns_with_environments
+    # rubocop:disable Metrics/ParameterLists
+    def self.build(environments: {}, outer_scope: {}, registers: {}, rethrow_errors: false, resource_limits: nil, static_environments: {}, &block)
+      new(environments, outer_scope, registers, rethrow_errors, resource_limits, static_environments, &block)
+    end
 
-      @this_stack_used = false
+    def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil, static_environments = {})
+      @environments = [environments]
+      @environments.flatten!
 
+      @static_environments = [static_environments].flat_map(&:freeze).freeze
+      @scopes              = [(outer_scope || {})]
+      @registers           = registers
+      @errors              = []
+      @partial             = false
+      @strict_variables    = false
+      @resource_limits     = resource_limits || ResourceLimits.new(Template.default_resource_limits)
+      @base_scope_depth    = 0
+      @interrupts          = []
+      @filters             = []
+      @global_filter       = nil
+      @disabled_tags       = {}
+
+      self.exception_renderer = Template.default_exception_renderer
       if rethrow_errors
-        self.exception_handler = ->(e) { true }
+        self.exception_renderer = Liquid::RAISE_EXCEPTION_LAMBDA
       end
 
-      @interrupts = []
-      @filters = []
+      yield self if block_given?
+
+      # Do this last, since it could result in this object being passed to a Proc in the environment
+      squash_instance_assigns_with_environments
+    end
+    # rubocop:enable Metrics/ParameterLists
+
+    def warnings
+      @warnings ||= []
     end
 
     def strainer
-      @strainer ||= Strainer.create(self, @filters)
+      @strainer ||= StrainerFactory.create(self, @filters)
     end
 
     # Adds filters to this context.
@@ -48,8 +69,12 @@ module Liquid
       @strainer = nil
     end
 
+    def apply_global_filter(obj)
+      global_filter.nil? ? obj : global_filter.call(obj)
+    end
+
     # are there any not handled interrupts?
-    def has_interrupt?
+    def interrupt?
       !@interrupts.empty?
     end
 
@@ -63,15 +88,12 @@ module Liquid
       @interrupts.pop
     end
 
-
-    def handle_error(e, token=nil)
-      if e.is_a?(Liquid::Error)
-        e.set_line_number_from_token(token)
-      end
-
+    def handle_error(e, line_number = nil)
+      e = internal_error unless e.is_a?(Liquid::Error)
+      e.template_name ||= template_name
+      e.line_number   ||= line_number
       errors.push(e)
-      raise if exception_handler && exception_handler.call(e)
-      Liquid::Error.render(e)
+      exception_renderer.call(e).to_s
     end
 
     def invoke(method, *args)
@@ -79,9 +101,9 @@ module Liquid
     end
 
     # Push new local scope on the stack. use <tt>Context#stack</tt> instead
-    def push(new_scope={})
+    def push(new_scope = {})
       @scopes.unshift(new_scope)
-      raise StackLevelError, "Nesting too deep".freeze if @scopes.length > 100
+      check_overflow
     end
 
     # Merge a hash of variables in the current local scope
@@ -103,19 +125,31 @@ module Liquid
     #   end
     #
     #   context['var]  #=> nil
-    def stack(new_scope=nil)
-      old_stack_used = @this_stack_used
-      if new_scope
-        push(new_scope)
-        @this_stack_used = true
-      else
-        @this_stack_used = false
-      end
-
+    def stack(new_scope = {})
+      push(new_scope)
       yield
     ensure
-      pop if @this_stack_used
-      @this_stack_used = old_stack_used
+      pop
+    end
+
+    # Creates a new context inheriting resource limits, filters, environment etc.,
+    # but with an isolated scope.
+    def new_isolated_subcontext
+      check_overflow
+
+      self.class.build(
+        resource_limits: resource_limits,
+        static_environments: static_environments,
+        registers: StaticRegisters.new(registers)
+      ).tap do |subcontext|
+        subcontext.base_scope_depth   = base_scope_depth + 1
+        subcontext.exception_renderer = exception_renderer
+        subcontext.filters  = @filters
+        subcontext.strainer = nil
+        subcontext.errors   = errors
+        subcontext.warnings = warnings
+        subcontext.disabled_tags = @disabled_tags
+      end
     end
 
     def clear_instance_assigns
@@ -124,10 +158,6 @@ module Liquid
 
     # Only allow String, Numeric, Hash, Array, Proc, Boolean or <tt>Liquid::Drop</tt>
     def []=(key, value)
-      unless @this_stack_used
-        @this_stack_used = true
-        push({})
-      end
       @scopes[0][key] = value
     end
 
@@ -143,7 +173,7 @@ module Liquid
       evaluate(Expression.parse(expression))
     end
 
-    def has_key?(key)
+    def key?(key)
       self[key] != nil
     end
 
@@ -152,52 +182,100 @@ module Liquid
     end
 
     # Fetches an object starting at the local scope and then moving up the hierachy
-    def find_variable(key)
-
+    def find_variable(key, raise_on_not_found: true)
       # This was changed from find() to find_index() because this is a very hot
       # path and find_index() is optimized in MRI to reduce object allocation
-      index = @scopes.find_index { |s| s.has_key?(key) }
-      scope = @scopes[index] if index
+      index = @scopes.find_index { |s| s.key?(key) }
 
-      variable = nil
-
-      if scope.nil?
-        @environments.each do |e|
-          variable = lookup_and_evaluate(e, key)
-          unless variable.nil?
-            scope = e
-            break
-          end
-        end
+      variable = if index
+        lookup_and_evaluate(@scopes[index], key, raise_on_not_found: raise_on_not_found)
+      else
+        try_variable_find_in_environments(key, raise_on_not_found: raise_on_not_found)
       end
 
-      scope     ||= @environments.last || @scopes.last
-      variable  ||= lookup_and_evaluate(scope, key)
-
-      variable = variable.to_liquid
+      variable         = variable.to_liquid
       variable.context = self if variable.respond_to?(:context=)
 
-      return variable
+      variable
     end
 
-    def lookup_and_evaluate(obj, key)
-      if (value = obj[key]).is_a?(Proc) && obj.respond_to?(:[]=)
-        obj[key] = (value.arity == 0) ? value.call : value.call(self)
+    def lookup_and_evaluate(obj, key, raise_on_not_found: true)
+      if @strict_variables && raise_on_not_found && obj.respond_to?(:key?) && !obj.key?(key)
+        raise Liquid::UndefinedVariable, "undefined variable #{key}"
+      end
+
+      value = obj[key]
+
+      if value.is_a?(Proc) && obj.respond_to?(:[]=)
+        obj[key] = value.arity == 0 ? value.call : value.call(self)
       else
         value
       end
     end
 
+    def with_disabled_tags(tag_names)
+      tag_names.each do |name|
+        @disabled_tags[name] = @disabled_tags.fetch(name, 0) + 1
+      end
+      yield
+    ensure
+      tag_names.each do |name|
+        @disabled_tags[name] -= 1
+      end
+    end
+
+    def tag_disabled?(tag_name)
+      @disabled_tags.fetch(tag_name, 0) > 0
+    end
+
+    protected
+
+    attr_writer :base_scope_depth, :warnings, :errors, :strainer, :filters, :disabled_tags
+
     private
-      def squash_instance_assigns_with_environments
-        @scopes.last.each_key do |k|
-          @environments.each do |env|
-            if env.has_key?(k)
-              scopes.last[k] = lookup_and_evaluate(env, k)
-              break
-            end
+
+    attr_reader :base_scope_depth
+
+    def try_variable_find_in_environments(key, raise_on_not_found:)
+      @environments.each do |environment|
+        found_variable = lookup_and_evaluate(environment, key, raise_on_not_found: raise_on_not_found)
+        if !found_variable.nil? || @strict_variables && raise_on_not_found
+          return found_variable
+        end
+      end
+      @static_environments.each do |environment|
+        found_variable = lookup_and_evaluate(environment, key, raise_on_not_found: raise_on_not_found)
+        if !found_variable.nil? || @strict_variables && raise_on_not_found
+          return found_variable
+        end
+      end
+      nil
+    end
+
+    def check_overflow
+      raise StackLevelError, "Nesting too deep" if overflow?
+    end
+
+    def overflow?
+      base_scope_depth + @scopes.length > Block::MAX_DEPTH
+    end
+
+    def internal_error
+      # raise and catch to set backtrace and cause on exception
+      raise Liquid::InternalError, 'internal'
+    rescue Liquid::InternalError => exc
+      exc
+    end
+
+    def squash_instance_assigns_with_environments
+      @scopes.last.each_key do |k|
+        @environments.each do |env|
+          if env.key?(k)
+            scopes.last[k] = lookup_and_evaluate(env, k)
+            break
           end
         end
-      end # squash_instance_assigns_with_environments
+      end
+    end # squash_instance_assigns_with_environments
   end # Context
 end # Liquid

lib/liquid/document.rb

@@ -1,23 +1,64 @@
+# frozen_string_literal: true
+
 module Liquid
-  class Document < BlockBody
-    def self.parse(tokens, options)
-      doc = new
-      doc.parse(tokens, options)
+  class Document
+    def self.parse(tokens, parse_context)
+      doc = new(parse_context)
+      doc.parse(tokens, parse_context)
       doc
     end
 
-    def parse(tokens, options)
-      super do |end_tag_name, end_tag_params|
-        unknown_tag(end_tag_name, options) if end_tag_name
+    attr_reader :parse_context, :body
+
+    def initialize(parse_context)
+      @parse_context = parse_context
+      @body = new_body
+    end
+
+    def nodelist
+      @body.nodelist
+    end
+
+    def parse(tokenizer, parse_context)
+      while parse_body(tokenizer)
+      end
+      @body.freeze
+    rescue SyntaxError => e
+      e.line_number ||= parse_context.line_number
+      raise
+    end
+
+    def unknown_tag(tag, _markup, _tokenizer)
+      case tag
+      when 'else', 'end'
+        raise SyntaxError, parse_context.locale.t("errors.syntax.unexpected_outer_tag", tag: tag)
+      else
+        raise SyntaxError, parse_context.locale.t("errors.syntax.unknown_tag", tag: tag)
       end
     end
 
-    def unknown_tag(tag, options)
-      case tag
-      when 'else'.freeze, 'end'.freeze
-        raise SyntaxError.new(options[:locale].t("errors.syntax.unexpected_outer_tag".freeze, :tag => tag))
-      else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.unknown_tag".freeze, :tag => tag))
+    def render_to_output_buffer(context, output)
+      @body.render_to_output_buffer(context, output)
+    end
+
+    def render(context)
+      render_to_output_buffer(context, +'')
+    end
+
+    private
+
+    def new_body
+      parse_context.new_block_body
+    end
+
+    def parse_body(tokenizer)
+      @body.parse(tokenizer, parse_context) do |unknown_tag_name, unknown_tag_markup|
+        if unknown_tag_name
+          unknown_tag(unknown_tag_name, unknown_tag_markup, tokenizer)
+          true
+        else
+          false
+        end
       end
     end
   end

lib/liquid/drop.rb

@@ -1,7 +1,8 @@
+# frozen_string_literal: true
+
 require 'set'
 
 module Liquid
-
   # A drop in liquid is a class which allows you to export DOM like things to liquid.
   # Methods of drops are callable.
   # The main use for liquid drops is to implement lazy loaded objects.
@@ -19,28 +20,27 @@ module Liquid
   #   tmpl = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {%endfor%} '  )
   #   tmpl.render('product' => ProductDrop.new ) # will invoke top_sales query.
   #
-  # Your drop can either implement the methods sans any parameters or implement the before_method(name) method which is a
-  # catch all.
+  # Your drop can either implement the methods sans any parameters
+  # or implement the liquid_method_missing(name) method which is a catch all.
   class Drop
     attr_writer :context
 
-    EMPTY_STRING = ''.freeze
-
     # Catch all for the method
-    def before_method(method)
-      nil
+    def liquid_method_missing(method)
+      return nil unless @context&.strict_variables
+      raise Liquid::UndefinedDropMethod, "undefined method #{method}"
     end
 
     # called by liquid to invoke a drop
     def invoke_drop(method_or_key)
-      if method_or_key && method_or_key != EMPTY_STRING && self.class.invokable?(method_or_key)
+      if self.class.invokable?(method_or_key)
         send(method_or_key)
       else
-        before_method(method_or_key)
+        liquid_method_missing(method_or_key)
       end
     end
 
-    def has_key?(name)
+    def key?(_name)
       true
     end
 
@@ -56,26 +56,25 @@ module Liquid
       self.class.name
     end
 
-    alias :[] :invoke_drop
-
-    private
+    alias_method :[], :invoke_drop
 
     # Check for method existence without invoking respond_to?, which creates symbols
     def self.invokable?(method_name)
-      self.invokable_methods.include?(method_name.to_s)
+      invokable_methods.include?(method_name.to_s)
     end
 
     def self.invokable_methods
-      unless @invokable_methods
+      @invokable_methods ||= begin
         blacklist = Liquid::Drop.public_instance_methods + [:each]
+
         if include?(Enumerable)
           blacklist += Enumerable.public_instance_methods
-          blacklist -= [:sort, :count, :first, :min, :max, :include?]
+          blacklist -= [:sort, :count, :first, :min, :max]
         end
+
         whitelist = [:to_liquid] + (public_instance_methods - blacklist)
-        @invokable_methods = Set.new(whitelist.map(&:to_s))
+        Set.new(whitelist.map(&:to_s))
       end
-      @invokable_methods
     end
   end
 end

lib/liquid/errors.rb

@@ -1,10 +1,13 @@
+# frozen_string_literal: true
+
 module Liquid
   class Error < ::StandardError
     attr_accessor :line_number
+    attr_accessor :template_name
     attr_accessor :markup_context
 
-    def to_s(with_prefix=true)
-      str = ""
+    def to_s(with_prefix = true)
+      str = +""
       str << message_prefix if with_prefix
       str << super()
 
@@ -16,32 +19,20 @@ module Liquid
       str
     end
 
-    def set_line_number_from_token(token)
-      return unless token.respond_to?(:line_number)
-      return if self.line_number
-      self.line_number = token.line_number
-    end
-
-    def self.render(e)
-      if e.is_a?(Liquid::Error)
-        e.to_s
-      else
-        "Liquid error: #{e.to_s}"
-      end
-    end
-
     private
 
     def message_prefix
-      str = ""
-      if is_a?(SyntaxError)
-        str << "Liquid syntax error"
+      str = +""
+      str << if is_a?(SyntaxError)
+        "Liquid syntax error"
       else
-        str << "Liquid error"
+        "Liquid error"
       end
 
       if line_number
-        str << " (line #{line_number})"
+        str << " ("
+        str << template_name << " " if template_name
+        str << "line " << line_number.to_s << ")"
       end
 
       str << ": "
@@ -49,12 +40,19 @@ module Liquid
     end
   end
 
-  class ArgumentError < Error; end
-  class ContextError < Error; end
-  class FileSystemError < Error; end
-  class StandardError < Error; end
-  class SyntaxError < Error; end
-  class StackLevelError < Error; end
-  class TaintedError < Error; end
-  class MemoryError < Error; end
+  ArgumentError       = Class.new(Error)
+  ContextError        = Class.new(Error)
+  FileSystemError     = Class.new(Error)
+  StandardError       = Class.new(Error)
+  SyntaxError         = Class.new(Error)
+  StackLevelError     = Class.new(Error)
+  MemoryError         = Class.new(Error)
+  ZeroDivisionError   = Class.new(Error)
+  FloatDomainError    = Class.new(Error)
+  UndefinedVariable   = Class.new(Error)
+  UndefinedDropMethod = Class.new(Error)
+  UndefinedFilter     = Class.new(Error)
+  MethodOverrideError = Class.new(Error)
+  DisabledError       = Class.new(Error)
+  InternalError       = Class.new(Error)
 end

lib/liquid/expression.rb

@@ -1,48 +1,44 @@
+# frozen_string_literal: true
+
 module Liquid
   class Expression
     LITERALS = {
-      nil => nil, 'nil'.freeze => nil, 'null'.freeze => nil, ''.freeze => nil,
-      'true'.freeze  => true,
-      'false'.freeze => false,
-      'blank'.freeze => :blank?,
-      'empty'.freeze => :empty?
-    }
+      nil => nil, 'nil' => nil, 'null' => nil, '' => nil,
+      'true' => true,
+      'false' => false,
+      'blank' => '',
+      'empty' => ''
+    }.freeze
 
-    INVERTED_LITERALS = LITERALS.invert
+    SINGLE_QUOTED_STRING = /\A\s*'(.*)'\s*\z/m
+    DOUBLE_QUOTED_STRING = /\A\s*"(.*)"\s*\z/m
+    INTEGERS_REGEX       = /\A\s*(-?\d+)\s*\z/
+    FLOATS_REGEX         = /\A\s*(-?\d[\d\.]+)\s*\z/
+
+    # Use an atomic group (?>...) to avoid pathological backtracing from
+    # malicious input as described in https://github.com/Shopify/liquid/issues/1357
+    RANGES_REGEX         = /\A\s*\(\s*(?>(\S+)\s*\.\.)\s*(\S+)\s*\)\s*\z/
 
     def self.parse(markup)
-      if LITERALS.key?(markup)
-        LITERALS[markup]
+      case markup
+      when nil
+        nil
+      when SINGLE_QUOTED_STRING, DOUBLE_QUOTED_STRING
+        Regexp.last_match(1)
+      when INTEGERS_REGEX
+        Regexp.last_match(1).to_i
+      when RANGES_REGEX
+        RangeLookup.parse(Regexp.last_match(1), Regexp.last_match(2))
+      when FLOATS_REGEX
+        Regexp.last_match(1).to_f
       else
-        case markup
-        when /\A'(.*)'\z/m # Single quoted strings
-          $1
-        when /\A"(.*)"\z/m # Double quoted strings
-          $1
-        when /\A(-?\d+)\z/ # Integer and floats
-          $1.to_i
-        when /\A\((\S+)\.\.(\S+)\)\z/ # Ranges
-          RangeLookup.parse($1, $2)
-        when /\A(-?\d[\d\.]+)\z/ # Floats
-          $1.to_f
+        markup = markup.strip
+        if LITERALS.key?(markup)
+          LITERALS[markup]
         else
           VariableLookup.parse(markup)
         end
       end
     end
-
-    def self.format(value)
-      if INVERTED_LITERALS.key?(value)
-        INVERTED_LITERALS[value].dup
-      elsif value.is_a?(VariableLookup) || value.is_a?(RangeLookup)
-        value.format
-      elsif value.is_a?(String)
-        "\"#{value}\""
-      elsif value.is_a?(Range)
-        "(#{value.to_s})"
-      else
-        value.to_s
-      end
-    end
   end
 end

lib/liquid/extensions.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'time'
 require 'date'
 
@@ -7,44 +9,56 @@ class String # :nodoc:
   end
 end
 
-class Array  # :nodoc:
+class Symbol # :nodoc:
+  def to_liquid
+    to_s
+  end
+end
+
+class Array # :nodoc:
   def to_liquid
     self
   end
 end
 
-class Hash  # :nodoc:
+class Hash # :nodoc:
   def to_liquid
     self
   end
 end
 
-class Numeric  # :nodoc:
+class Numeric # :nodoc:
   def to_liquid
     self
   end
 end
 
-class Time  # :nodoc:
+class Range # :nodoc:
   def to_liquid
     self
   end
 end
 
-class DateTime < Date  # :nodoc:
+class Time # :nodoc:
   def to_liquid
     self
   end
 end
 
-class Date  # :nodoc:
+class DateTime < Date # :nodoc:
+  def to_liquid
+    self
+  end
+end
+
+class Date # :nodoc:
   def to_liquid
     self
   end
 end
 
 class TrueClass
-  def to_liquid  # :nodoc:
+  def to_liquid # :nodoc:
     self
   end
 end

lib/liquid/file_system.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # A Liquid file system is a way to let your templates retrieve other templates for use with the include tag.
   #
@@ -8,13 +10,13 @@ module Liquid
   #
   # Example:
   #
-  # Liquid::Template.file_system = Liquid::LocalFileSystem.new(template_path)
-  # liquid = Liquid::Template.parse(template)
+  #   Liquid::Template.file_system = Liquid::LocalFileSystem.new(template_path)
+  #   liquid = Liquid::Template.parse(template)
   #
   # This will parse the template with a LocalFileSystem implementation rooted at 'template_path'.
   class BlankFileSystem
     # Called by Liquid to retrieve a template file
-    def read_template_file(template_path)
+    def read_template_file(_template_path)
       raise FileSystemError, "This liquid context does not allow includes."
     end
   end
@@ -26,10 +28,10 @@ module Liquid
   #
   # Example:
   #
-  # file_system = Liquid::LocalFileSystem.new("/some/path")
+  #   file_system = Liquid::LocalFileSystem.new("/some/path")
   #
-  # file_system.full_path("mypartial")       # => "/some/path/_mypartial.liquid"
-  # file_system.full_path("dir/mypartial")   # => "/some/path/dir/_mypartial.liquid"
+  #   file_system.full_path("mypartial")       # => "/some/path/_mypartial.liquid"
+  #   file_system.full_path("dir/mypartial")   # => "/some/path/dir/_mypartial.liquid"
   #
   # Optionally in the second argument you can specify a custom pattern for template filenames.
   # The Kernel::sprintf format specification is used.
@@ -37,35 +39,35 @@ module Liquid
   #
   # Example:
   #
-  # file_system = Liquid::LocalFileSystem.new("/some/path", "%s.html")
+  #   file_system = Liquid::LocalFileSystem.new("/some/path", "%s.html")
   #
-  # file_system.full_path("index") # => "/some/path/index.html"
+  #   file_system.full_path("index") # => "/some/path/index.html"
   #
   class LocalFileSystem
     attr_accessor :root
 
-    def initialize(root, pattern = "_%s.liquid".freeze)
-      @root = root
+    def initialize(root, pattern = "_%s.liquid")
+      @root    = root
       @pattern = pattern
     end
 
     def read_template_file(template_path)
       full_path = full_path(template_path)
-      raise FileSystemError, "No such template '#{template_path}'" unless File.exists?(full_path)
+      raise FileSystemError, "No such template '#{template_path}'" unless File.exist?(full_path)
 
       File.read(full_path)
     end
 
     def full_path(template_path)
-      raise FileSystemError, "Illegal template name '#{template_path}'" unless template_path =~ /\A[^.\/][a-zA-Z0-9_\/]+\z/
+      raise FileSystemError, "Illegal template name '#{template_path}'" unless %r{\A[^./][a-zA-Z0-9_/]+\z}.match?(template_path)
 
-      full_path = if template_path.include?('/'.freeze)
+      full_path = if template_path.include?('/')
         File.join(root, File.dirname(template_path), @pattern % File.basename(template_path))
       else
         File.join(root, @pattern % template_path)
       end
 
-      raise FileSystemError, "Illegal template path '#{File.expand_path(full_path)}'" unless File.expand_path(full_path) =~ /\A#{File.expand_path(root)}/
+      raise FileSystemError, "Illegal template path '#{File.expand_path(full_path)}'" unless File.expand_path(full_path).start_with?(File.expand_path(root))
 
       full_path
     end

lib/liquid/forloop_drop.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module Liquid
+  class ForloopDrop < Drop
+    def initialize(name, length, parentloop)
+      @name       = name
+      @length     = length
+      @parentloop = parentloop
+      @index      = 0
+    end
+
+    attr_reader :length, :parentloop
+
+    def name
+      Usage.increment('forloop_drop_name')
+      @name
+    end
+
+    def index
+      @index + 1
+    end
+
+    def index0
+      @index
+    end
+
+    def rindex
+      @length - @index
+    end
+
+    def rindex0
+      @length - @index - 1
+    end
+
+    def first
+      @index == 0
+    end
+
+    def last
+      @index == @length - 1
+    end
+
+    protected
+
+    def increment!
+      @index += 1
+    end
+  end
+end

lib/liquid/i18n.rb

@@ -1,11 +1,12 @@
+# frozen_string_literal: true
+
 require 'yaml'
 
 module Liquid
   class I18n
-    DEFAULT_LOCALE = File.join(File.expand_path(File.dirname(__FILE__)), "locales", "en.yml")
+    DEFAULT_LOCALE = File.join(File.expand_path(__dir__), "locales", "en.yml")
 
-    class TranslationError < StandardError
-    end
+    TranslationError = Class.new(StandardError)
 
     attr_reader :path
 
@@ -23,16 +24,17 @@ module Liquid
     end
 
     private
+
     def interpolate(name, vars)
-      name.gsub(/%\{(\w+)\}/) {
+      name.gsub(/%\{(\w+)\}/) do
         # raise TranslationError, "Undefined key #{$1} for interpolation in translation #{name}"  unless vars[$1.to_sym]
-        "#{vars[$1.to_sym]}"
-      }
+        (vars[Regexp.last_match(1).to_sym]).to_s
+      end
     end
 
     def deep_fetch_translation(name)
-      name.split('.'.freeze).reduce(locale) do |level, cur|
-        level[cur] or raise TranslationError, "Translation for #{name} does not exist in locale #{path}"
+      name.split('.').reduce(locale) do |level, cur|
+        level[cur] || raise(TranslationError, "Translation for #{name} does not exist in locale #{path}")
       end
     end
   end

lib/liquid/interrupts.rb

@@ -1,11 +1,12 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # An interrupt is any command that breaks processing of a block (ex: a for loop).
   class Interrupt
     attr_reader :message
 
-    def initialize(message=nil)
-      @message = message || "interrupt".freeze
+    def initialize(message = nil)
+      @message = message || "interrupt"
     end
   end
 

lib/liquid/lexer.rb

@@ -1,45 +1,54 @@
+# frozen_string_literal: true
+
 require "strscan"
 module Liquid
   class Lexer
     SPECIALS = {
-      '|'.freeze => :pipe,
-      '.'.freeze => :dot,
-      ':'.freeze => :colon,
-      ','.freeze => :comma,
-      '['.freeze => :open_square,
-      ']'.freeze => :close_square,
-      '('.freeze => :open_round,
-      ')'.freeze => :close_round,
-      '?'.freeze => :question,
-      '-'.freeze => :dash
-    }
-    IDENTIFIER = /[a-zA-Z_][\w-]*\??/
+      '|' => :pipe,
+      '.' => :dot,
+      ':' => :colon,
+      ',' => :comma,
+      '[' => :open_square,
+      ']' => :close_square,
+      '(' => :open_round,
+      ')' => :close_round,
+      '?' => :question,
+      '-' => :dash,
+    }.freeze
+    IDENTIFIER            = /[a-zA-Z_][\w-]*\??/
     SINGLE_STRING_LITERAL = /'[^\']*'/
     DOUBLE_STRING_LITERAL = /"[^\"]*"/
-    NUMBER_LITERAL = /-?\d+(\.\d+)?/
-    DOTDOT = /\.\./
-    COMPARISON_OPERATOR = /==|!=|<>|<=?|>=?|contains/
+    NUMBER_LITERAL        = /-?\d+(\.\d+)?/
+    DOTDOT                = /\.\./
+    COMPARISON_OPERATOR   = /==|!=|<>|<=?|>=?|contains(?=\s)/
+    WHITESPACE_OR_NOTHING = /\s*/
 
     def initialize(input)
-      @ss = StringScanner.new(input.rstrip)
+      @ss = StringScanner.new(input)
     end
 
     def tokenize
       @output = []
 
-      while !@ss.eos?
-        @ss.skip(/\s*/)
-        tok = case
-        when t = @ss.scan(COMPARISON_OPERATOR) then [:comparison, t]
-        when t = @ss.scan(SINGLE_STRING_LITERAL) then [:string, t]
-        when t = @ss.scan(DOUBLE_STRING_LITERAL) then [:string, t]
-        when t = @ss.scan(NUMBER_LITERAL) then [:number, t]
-        when t = @ss.scan(IDENTIFIER) then [:id, t]
-        when t = @ss.scan(DOTDOT) then [:dotdot, t]
+      until @ss.eos?
+        @ss.skip(WHITESPACE_OR_NOTHING)
+        break if @ss.eos?
+        tok      = if (t = @ss.scan(COMPARISON_OPERATOR))
+          [:comparison, t]
+        elsif (t = @ss.scan(SINGLE_STRING_LITERAL))
+          [:string, t]
+        elsif (t = @ss.scan(DOUBLE_STRING_LITERAL))
+          [:string, t]
+        elsif (t = @ss.scan(NUMBER_LITERAL))
+          [:number, t]
+        elsif (t = @ss.scan(IDENTIFIER))
+          [:id, t]
+        elsif (t = @ss.scan(DOTDOT))
+          [:dotdot, t]
         else
-          c = @ss.getch
-          if s = SPECIALS[c]
-            [s,c]
+          c     = @ss.getch
+          if (s = SPECIALS[c])
+            [s, c]
           else
             raise SyntaxError, "Unexpected character #{c}"
           end

lib/liquid/locales/en.yml

@@ -1,6 +1,7 @@
 ---
   errors:
     syntax:
+      tag_unexpected_args: "Syntax Error in '%{tag}' - Valid syntax: %{tag}"
       assign: "Syntax Error in 'assign' - Valid syntax: assign [var] = [source]"
       capture: "Syntax Error in 'capture' - Valid syntax: capture [var]"
       case: "Syntax Error in 'case' - Valid syntax: case [condition]"
@@ -13,11 +14,15 @@
       if: "Syntax Error in tag 'if' - Valid syntax: if [expression]"
       include: "Error in tag 'include' - Valid syntax: include '[template]' (with|for) [object|collection]"
       unknown_tag: "Unknown tag '%{tag}'"
-      invalid_delimiter: "'end' is not a valid delimiter for %{block_name} tags. use %{block_delimiter}"
+      invalid_delimiter: "'%{tag}' is not a valid delimiter for %{block_name} tags. use %{block_delimiter}"
       unexpected_else: "%{block_name} tag does not expect 'else' tag"
       unexpected_outer_tag: "Unexpected outer '%{tag}' tag"
       tag_termination: "Tag '%{token}' was not properly terminated with regexp: %{tag_end}"
       variable_termination: "Variable '%{token}' was not properly terminated with regexp: %{tag_end}"
       tag_never_closed: "'%{block_name}' tag was never closed"
-      meta_syntax_error: "Liquid syntax error: #{e.message}"
       table_row: "Syntax Error in 'table_row loop' - Valid syntax: table_row [item] in [collection] cols=3"
+      render: "Syntax error in tag 'render' - Template name must be a quoted string"
+    argument:
+      include: "Argument error in tag 'include' - Illegal template name"
+    disabled:
+      tag: "usage is not allowed in this context"

lib/liquid/module_ex.rb

@@ -1,64 +0,0 @@
-# Copyright 2007 by Domizio Demichelis
-# This library is free software. It may be used, redistributed and/or modified
-# under the same terms as Ruby itself
-#
-# This extension is used in order to expose the object of the implementing class
-# to liquid as it were a Drop. It also limits the liquid-callable methods of the instance
-# to the allowed method passed with the liquid_methods call
-# Example:
-#
-#   class SomeClass
-#     liquid_methods :an_allowed_method
-#
-#     def an_allowed_method
-#       'this comes from an allowed method'
-#     end
-#
-#     def unallowed_method
-#       'this will never be an output'
-#     end
-#   end
-#
-# if you want to extend the drop to other methods you can defines more methods
-# in the class <YourClass>::LiquidDropClass
-#
-#   class SomeClass::LiquidDropClass
-#     def another_allowed_method
-#       'and this from another allowed method'
-#     end
-#   end
-#
-#
-# usage:
-#   @something = SomeClass.new
-#
-# template:
-#   {{something.an_allowed_method}}{{something.unallowed_method}} {{something.another_allowed_method}}
-#
-# output:
-#   'this comes from an allowed method and this from another allowed method'
-#
-# You can also chain associations, by adding the liquid_method call in the
-# association models.
-#
-class Module
-  def liquid_methods(*allowed_methods)
-    drop_class = eval "class #{self.to_s}::LiquidDropClass < Liquid::Drop; self; end"
-    
-    define_method :to_liquid do
-      drop_class.new(self)
-    end
-    
-    drop_class.class_eval do
-      def initialize(object)
-        @object = object
-      end
-      
-      allowed_methods.each do |sym|
-        define_method sym do
-          @object.send sym
-        end
-      end
-    end
-  end
-end

lib/liquid/parse_context.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Liquid
+  class ParseContext
+    attr_accessor :locale, :line_number, :trim_whitespace, :depth
+    attr_reader :partial, :warnings, :error_mode
+
+    def initialize(options = {})
+      @template_options = options ? options.dup : {}
+
+      @locale   = @template_options[:locale] ||= I18n.new
+      @warnings = []
+
+      self.depth   = 0
+      self.partial = false
+    end
+
+    def [](option_key)
+      @options[option_key]
+    end
+
+    def new_block_body
+      Liquid::BlockBody.new
+    end
+
+    def new_tokenizer(markup, start_line_number: nil, for_liquid_tag: false)
+      Tokenizer.new(markup, line_number: start_line_number, for_liquid_tag: for_liquid_tag)
+    end
+
+    def parse_expression(markup)
+      Expression.parse(markup)
+    end
+
+    def partial=(value)
+      @partial = value
+      @options = value ? partial_options : @template_options
+
+      @error_mode = @options[:error_mode] || Template.error_mode
+    end
+
+    def partial_options
+      @partial_options ||= begin
+        dont_pass = @template_options[:include_options_blacklist]
+        if dont_pass == true
+          { locale: locale }
+        elsif dont_pass.is_a?(Array)
+          @template_options.reject { |k, _v| dont_pass.include?(k) }
+        else
+          @template_options
+        end
+      end
+    end
+  end
+end

lib/liquid/parse_tree_visitor.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Liquid
+  class ParseTreeVisitor
+    def self.for(node, callbacks = Hash.new(proc {}))
+      if defined?(node.class::ParseTreeVisitor)
+        node.class::ParseTreeVisitor
+      else
+        self
+      end.new(node, callbacks)
+    end
+
+    def initialize(node, callbacks)
+      @node      = node
+      @callbacks = callbacks
+    end
+
+    def add_callback_for(*classes, &block)
+      callback = block
+      callback = ->(node, _) { yield node } if block.arity.abs == 1
+      callback = ->(_, _) { yield } if block.arity.zero?
+      classes.each { |klass| @callbacks[klass] = callback }
+      self
+    end
+
+    def visit(context = nil)
+      children.map do |node|
+        item, new_context = @callbacks[node.class].call(node, context)
+        [
+          item,
+          ParseTreeVisitor.for(node, @callbacks).visit(new_context || context),
+        ]
+      end
+    end
+
+    protected
+
+    def children
+      @node.respond_to?(:nodelist) ? Array(@node.nodelist) : []
+    end
+  end
+end

lib/liquid/parser.rb

@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 module Liquid
   class Parser
     def initialize(input)
-      l = Lexer.new(input)
+      l       = Lexer.new(input)
       @tokens = l.tokenize
-      @p = 0 # pointer to current location
+      @p      = 0 # pointer to current location
     end
 
     def jump(point)
@@ -46,11 +48,18 @@ module Liquid
 
     def expression
       token = @tokens[@p]
-      if token[0] == :id
-        variable_signature
-      elsif [:string, :number].include? token[0]
+      case token[0]
+      when :id
+        str = consume
+        str << variable_lookups
+      when :open_square
+        str = consume
+        str << expression
+        str << consume(:close_square)
+        str << variable_lookups
+      when :string, :number
         consume
-      elsif token.first == :open_round
+      when :open_round
         consume
         first = expression
         consume(:dotdot)
@@ -63,26 +72,29 @@ module Liquid
     end
 
     def argument
-      str = ""
+      str = +""
       # might be a keyword argument (identifier: expression)
       if look(:id) && look(:colon, 1)
-        str << consume << consume << ' '.freeze
+        str << consume << consume << ' '
       end
 
       str << expression
       str
     end
 
-    def variable_signature
-      str = consume(:id)
-      if look(:open_square)
-        str << consume
-        str << expression
-        str << consume(:close_square)
-      end
-      if look(:dot)
-        str << consume
-        str << variable_signature
+    def variable_lookups
+      str = +""
+      loop do
+        if look(:open_square)
+          str << consume
+          str << expression
+          str << consume(:close_square)
+        elsif look(:dot)
+          str << consume
+          str << consume(:id)
+        else
+          break
+        end
       end
       str
     end

lib/liquid/parser_switching.rb

@@ -1,25 +1,39 @@
+# frozen_string_literal: true
+
 module Liquid
   module ParserSwitching
+    def strict_parse_with_error_mode_fallback(markup)
+      strict_parse_with_error_context(markup)
+    rescue SyntaxError => e
+      case parse_context.error_mode
+      when :strict
+        raise
+      when :warn
+        parse_context.warnings << e
+      end
+      lax_parse(markup)
+    end
+
     def parse_with_selected_parser(markup)
-      case @options[:error_mode] || Template.error_mode
+      case parse_context.error_mode
       when :strict then strict_parse_with_error_context(markup)
       when :lax    then lax_parse(markup)
       when :warn
         begin
-          return strict_parse_with_error_context(markup)
+          strict_parse_with_error_context(markup)
         rescue SyntaxError => e
-          e.set_line_number_from_token(markup)
-          @warnings ||= []
-          @warnings << e
-          return lax_parse(markup)
+          parse_context.warnings << e
+          lax_parse(markup)
         end
       end
     end
 
     private
+
     def strict_parse_with_error_context(markup)
       strict_parse(markup)
     rescue SyntaxError => e
+      e.line_number    = line_number
       e.markup_context = markup_context(markup)
       raise e
     end

lib/liquid/partial_cache.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Liquid
+  class PartialCache
+    def self.load(template_name, context:, parse_context:)
+      cached_partials = (context.registers[:cached_partials] ||= {})
+      cached = cached_partials[template_name]
+      return cached if cached
+
+      file_system = (context.registers[:file_system] ||= Liquid::Template.file_system)
+      source      = file_system.read_template_file(template_name)
+
+      parse_context.partial = true
+
+      template_factory = (context.registers[:template_factory] ||= Liquid::TemplateFactory.new)
+      template = template_factory.for(template_name)
+
+      partial = template.parse(source, parse_context)
+      cached_partials[template_name] = partial
+    ensure
+      parse_context.partial = false
+    end
+  end
+end

lib/liquid/profiler.rb

@@ -1,7 +1,8 @@
+# frozen_string_literal: true
+
 require 'liquid/profiler/hooks'
 
 module Liquid
-
   # Profiler enables support for profiling template rendering to help track down performance issues.
   #
   # To enable profiling, first require 'liquid/profiler'.
@@ -20,11 +21,11 @@ module Liquid
   # inside of <tt>{% include %}</tt> tags.
   #
   #   profile.each do |node|
-  #     # Access to the token itself
+  #     # Access to the node itself
   #     node.code
   #
   #     # Which template and line number of this node.
-  #     # If top level, this will be "<root>".
+  #     # The top-level template name is `nil` by default, but can be set in the Liquid::Context before rendering.
   #     node.partial
   #     node.line_number
   #
@@ -45,118 +46,94 @@ module Liquid
     include Enumerable
 
     class Timing
-      attr_reader :code, :partial, :line_number, :children
+      attr_reader :code, :template_name, :line_number, :children
+      attr_accessor :total_time
+      alias_method :render_time, :total_time
+      alias_method :partial, :template_name
 
-      def initialize(token, partial)
-        @code        = token.respond_to?(:raw) ? token.raw : token
-        @partial     = partial
-        @line_number = token.respond_to?(:line_number) ? token.line_number : nil
-        @children    = []
+      def initialize(code: nil, template_name: nil, line_number: nil)
+        @code = code
+        @template_name = template_name
+        @line_number = line_number
+        @children = []
       end
 
-      def self.start(token, partial)
-        new(token, partial).tap do |t|
-          t.start
+      def self_time
+        @self_time ||= begin
+          total_children_time = 0.0
+          @children.each do |child|
+            total_children_time += child.total_time
+          end
+          @total_time - total_children_time
         end
       end
-
-      def start
-        @start_time = Time.now
-      end
-
-      def finish
-        @end_time = Time.now
-      end
-
-      def render_time
-        @end_time - @start_time
-      end
     end
 
-    def self.profile_token_render(token)
-      if Profiler.current_profile && token.respond_to?(:render)
-        Profiler.current_profile.start_token(token)
-        output = yield
-        Profiler.current_profile.end_token(token)
-        output
-      else
-        yield
-      end
-    end
-
-    def self.profile_children(template_name)
-      if Profiler.current_profile
-        Profiler.current_profile.push_partial(template_name)
-        output = yield
-        Profiler.current_profile.pop_partial
-        output
-      else
-        yield
-      end
-    end
-
-    def self.current_profile
-      Thread.current[:liquid_profiler]
-    end
+    attr_reader :total_time
+    alias_method :total_render_time, :total_time
 
     def initialize
-      @partial_stack = ["<root>"]
-
-      @root_timing = Timing.new("", current_partial)
-      @timing_stack = [@root_timing]
-
-      @render_start_at = Time.now
-      @render_end_at = @render_start_at
+      @root_children = []
+      @current_children = nil
+      @total_time = 0.0
     end
 
-    def start
-      Thread.current[:liquid_profiler] = self
-      @render_start_at = Time.now
+    def profile(template_name, &block)
+      # nested renders are done from a tag that already has a timing node
+      return yield if @current_children
+
+      root_children = @root_children
+      render_idx = root_children.length
+      begin
+        @current_children = root_children
+        profile_node(template_name, &block)
+      ensure
+        @current_children = nil
+        if (timing = root_children[render_idx])
+          @total_time += timing.total_time
+        end
+      end
     end
 
-    def stop
-      Thread.current[:liquid_profiler] = nil
-      @render_end_at = Time.now
-    end
-
-    def total_render_time
-      @render_end_at - @render_start_at
+    def children
+      children = @root_children
+      if children.length == 1
+        children.first.children
+      else
+        children
+      end
     end
 
     def each(&block)
-      @root_timing.children.each(&block)
+      children.each(&block)
     end
 
     def [](idx)
-      @root_timing.children[idx]
+      children[idx]
     end
 
     def length
-      @root_timing.children.length
+      children.length
     end
 
-    def start_token(token)
-      @timing_stack.push(Timing.start(token, current_partial))
+    def profile_node(template_name, code: nil, line_number: nil)
+      timing = Timing.new(code: code, template_name: template_name, line_number: line_number)
+      parent_children = @current_children
+      start_time = monotonic_time
+      begin
+        @current_children = timing.children
+        yield
+      ensure
+        @current_children = parent_children
+        timing.total_time = monotonic_time - start_time
+        parent_children << timing
+      end
     end
 
-    def end_token(token)
-      timing = @timing_stack.pop
-      timing.finish
+    private
 
-      @timing_stack.last.children << timing
+    def monotonic_time
+      Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
-
-    def current_partial
-      @partial_stack.last
-    end
-
-    def push_partial(partial_name)
-      @partial_stack.push(partial_name)
-    end
-
-    def pop_partial
-      @partial_stack.pop
-    end
-
   end
 end

lib/liquid/profiler/hooks.rb

@@ -1,23 +1,35 @@
+# frozen_string_literal: true
+
 module Liquid
-  class BlockBody
-    def render_token_with_profiling(token, context)
-      Profiler.profile_token_render(token) do
-        render_token_without_profiling(token, context)
+  module BlockBodyProfilingHook
+    def render_node(context, output, node)
+      if (profiler = context.profiler)
+        profiler.profile_node(context.template_name, code: node.raw, line_number: node.line_number) do
+          super
+        end
+      else
+        super
       end
     end
-
-    alias_method :render_token_without_profiling, :render_token
-    alias_method :render_token, :render_token_with_profiling
   end
+  BlockBody.prepend(BlockBodyProfilingHook)
 
-  class Include < Tag
-    def render_with_profiling(context)
-      Profiler.profile_children(context.evaluate(@template_name_expr).to_s) do
-        render_without_profiling(context)
-      end
+  module DocumentProfilingHook
+    def render_to_output_buffer(context, output)
+      return super unless context.profiler
+      context.profiler.profile(context.template_name) { super }
     end
-
-    alias_method :render_without_profiling, :render
-    alias_method :render, :render_with_profiling
   end
+  Document.prepend(DocumentProfilingHook)
+
+  module ContextProfilingHook
+    attr_accessor :profiler
+
+    def new_isolated_subcontext
+      new_context = super
+      new_context.profiler = profiler
+      new_context
+    end
+  end
+  Context.prepend(ContextProfilingHook)
 end

lib/liquid/range_lookup.rb

@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 module Liquid
   class RangeLookup
     def self.parse(start_markup, end_markup)
       start_obj = Expression.parse(start_markup)
-      end_obj = Expression.parse(end_markup)
+      end_obj   = Expression.parse(end_markup)
       if start_obj.respond_to?(:evaluate) || end_obj.respond_to?(:evaluate)
         new(start_obj, end_obj)
       else
@@ -12,15 +14,26 @@ module Liquid
 
     def initialize(start_obj, end_obj)
       @start_obj = start_obj
-      @end_obj = end_obj
+      @end_obj   = end_obj
     end
 
     def evaluate(context)
-      context.evaluate(@start_obj).to_i..context.evaluate(@end_obj).to_i
+      start_int = to_integer(context.evaluate(@start_obj))
+      end_int   = to_integer(context.evaluate(@end_obj))
+      start_int..end_int
     end
 
-    def format
-      "(#{Expression.format(@start_obj)}..#{Expression.format(@end_obj)})"
+    private
+
+    def to_integer(input)
+      case input
+      when Integer
+        input
+      when NilClass, String
+        input.to_i
+      else
+        Utils.to_integer(input)
+      end
     end
   end
 end

lib/liquid/register.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Register
+  end
+end

lib/liquid/resource_limits.rb

@@ -1,23 +1,62 @@
+# frozen_string_literal: true
+
 module Liquid
   class ResourceLimits
-    attr_accessor :render_length, :render_score, :assign_score,
-                  :render_length_limit, :render_score_limit, :assign_score_limit
+    attr_accessor :render_length_limit, :render_score_limit, :assign_score_limit
+    attr_reader :render_score, :assign_score
 
     def initialize(limits)
       @render_length_limit = limits[:render_length_limit]
-      @render_score_limit = limits[:render_score_limit]
-      @assign_score_limit = limits[:assign_score_limit]
+      @render_score_limit  = limits[:render_score_limit]
+      @assign_score_limit  = limits[:assign_score_limit]
       reset
     end
 
+    def increment_render_score(amount)
+      @render_score += amount
+      raise_limits_reached if @render_score_limit && @render_score > @render_score_limit
+    end
+
+    def increment_assign_score(amount)
+      @assign_score += amount
+      raise_limits_reached if @assign_score_limit && @assign_score > @assign_score_limit
+    end
+
+    # update either render_length or assign_score based on whether or not the writes are captured
+    def increment_write_score(output)
+      if (last_captured = @last_capture_length)
+        captured = output.bytesize
+        increment = captured - last_captured
+        @last_capture_length = captured
+        increment_assign_score(increment)
+      elsif @render_length_limit && output.bytesize > @render_length_limit
+        raise_limits_reached
+      end
+    end
+
+    def raise_limits_reached
+      @reached_limit = true
+      raise MemoryError, "Memory limits exceeded"
+    end
+
     def reached?
-      (@render_length_limit && @render_length > @render_length_limit) ||
-      (@render_score_limit  && @render_score  > @render_score_limit ) ||
-      (@assign_score_limit  && @assign_score  > @assign_score_limit )
+      @reached_limit
     end
 
     def reset
-      @render_length = @render_score = @assign_score = 0
+      @reached_limit = false
+      @last_capture_length = nil
+      @render_score = @assign_score = 0
+    end
+
+    def with_capture
+      old_capture_length = @last_capture_length
+      begin
+        @last_capture_length = 0
+        yield
+      ensure
+        @last_capture_length = old_capture_length
+      end
     end
   end
 end

lib/liquid/standardfilters.rb

@@ -1,17 +1,24 @@
+# frozen_string_literal: true
+
 require 'cgi'
 require 'bigdecimal'
 
 module Liquid
-
   module StandardFilters
     HTML_ESCAPE = {
-      '&'.freeze => '&'.freeze,
-      '>'.freeze => '>'.freeze,
-      '<'.freeze => '&lt;'.freeze,
-      '"'.freeze => '&quot;'.freeze,
-      "'".freeze => '&#39;'.freeze
-    }
+      '&' => '&amp;',
+      '>' => '&gt;',
+      '<' => '&lt;',
+      '"' => '&quot;',
+      "'" => '&#39;',
+    }.freeze
     HTML_ESCAPE_ONCE_REGEXP = /["><']|&(?!([a-zA-Z]+|(#\d+));)/
+    STRIP_HTML_BLOCKS       = Regexp.union(
+      %r{<script.*?</script>}m,
+      /<!--.*?-->/m,
+      %r{<style.*?</style>}m
+    )
+    STRIP_HTML_TAGS = /<.*?>/m
 
     # Return the size of an array or of an string
     def size(input)
@@ -34,7 +41,7 @@ module Liquid
     end
 
     def escape(input)
-      CGI.escapeHTML(input).untaint rescue input
+      CGI.escapeHTML(input.to_s) unless input.nil?
     end
     alias_method :h, :escape
 
@@ -43,12 +50,21 @@ module Liquid
     end
 
     def url_encode(input)
-      CGI.escape(input) rescue input
+      CGI.escape(input.to_s) unless input.nil?
     end
 
-    def slice(input, offset, length=nil)
-      offset = Integer(offset)
-      length = length ? Integer(length) : 1
+    def url_decode(input)
+      return if input.nil?
+
+      result = CGI.unescape(input.to_s)
+      raise Liquid::ArgumentError, "invalid byte sequence in #{result.encoding}" unless result.valid_encoding?
+
+      result
+    end
+
+    def slice(input, offset, length = nil)
+      offset = Utils.to_integer(offset)
+      length = length ? Utils.to_integer(length) : 1
 
       if input.is_a?(Array)
         input.slice(offset, length) || []
@@ -58,19 +74,28 @@ module Liquid
     end
 
     # Truncate a string down to x characters
-    def truncate(input, length = 50, truncate_string = "...".freeze)
-      if input.nil? then return end
-      l = length.to_i - truncate_string.length
+    def truncate(input, length = 50, truncate_string = "...")
+      return if input.nil?
+      input_str = input.to_s
+      length    = Utils.to_integer(length)
+
+      truncate_string_str = truncate_string.to_s
+
+      l = length - truncate_string_str.length
       l = 0 if l < 0
-      input.length > length.to_i ? input[0...l] + truncate_string : input
+
+      input_str.length > length ? input_str[0...l].concat(truncate_string_str) : input_str
     end
 
-    def truncatewords(input, words = 15, truncate_string = "...".freeze)
-      if input.nil? then return end
+    def truncatewords(input, words = 15, truncate_string = "...")
+      return if input.nil?
       wordlist = input.to_s.split
-      l = words.to_i - 1
+      words    = Utils.to_integer(words)
+
+      l = words - 1
       l = 0 if l < 0
-      wordlist.length > l ? wordlist[0..l].join(" ".freeze) + truncate_string : input
+
+      wordlist.length > l ? wordlist[0..l].join(" ").concat(truncate_string.to_s) : input
     end
 
     # Split input string into an array of substrings separated by given pattern.
@@ -79,7 +104,7 @@ module Liquid
     #   <div class="summary">{{ post | split '//' | first }}</div>
     #
     def split(input, pattern)
-      input.to_s.split(pattern)
+      input.to_s.split(pattern.to_s)
     end
 
     def strip(input)
@@ -95,95 +120,160 @@ module Liquid
     end
 
     def strip_html(input)
-      empty = ''.freeze
-      input.to_s.gsub(/<script.*?<\/script>/m, empty).gsub(/<!--.*?-->/m, empty).gsub(/<style.*?<\/style>/m, empty).gsub(/<.*?>/m, empty)
+      empty  = ''
+      result = input.to_s.gsub(STRIP_HTML_BLOCKS, empty)
+      result.gsub!(STRIP_HTML_TAGS, empty)
+      result
     end
 
     # Remove all newlines from the string
     def strip_newlines(input)
-      input.to_s.gsub(/\r?\n/, ''.freeze)
+      input.to_s.gsub(/\r?\n/, '')
     end
 
     # Join elements of the array with certain character between them
-    def join(input, glue = ' '.freeze)
-      InputIterator.new(input).join(glue)
+    def join(input, glue = ' ')
+      InputIterator.new(input, context).join(glue)
     end
 
     # Sort elements of the array
     # provide optional property with which to sort an array of hashes or drops
     def sort(input, property = nil)
-      ary = InputIterator.new(input)
+      ary = InputIterator.new(input, context)
+
+      return [] if ary.empty?
+
       if property.nil?
-        ary.sort
-      elsif ary.first.respond_to?(:[]) && !ary.first[property].nil?
-        ary.sort {|a,b| a[property] <=> b[property] }
-      elsif ary.first.respond_to?(property)
-        ary.sort {|a,b| a.send(property) <=> b.send(property) }
+        ary.sort do |a, b|
+          nil_safe_compare(a, b)
+        end
+      elsif ary.all? { |el| el.respond_to?(:[]) }
+        begin
+          ary.sort { |a, b| nil_safe_compare(a[property], b[property]) }
+        rescue TypeError
+          raise_property_error(property)
+        end
       end
     end
 
     # Sort elements of an array ignoring case if strings
     # provide optional property with which to sort an array of hashes or drops
     def sort_natural(input, property = nil)
-      ary = InputIterator.new(input)
+      ary = InputIterator.new(input, context)
+
+      return [] if ary.empty?
 
       if property.nil?
-        ary.sort {|a,b| a.casecmp(b) }
-      elsif ary.first.respond_to?(:[]) && !ary.first[property].nil?
-        ary.sort {|a,b| a[property].casecmp(b[property]) }
-      elsif ary.first.respond_to?(property)
-        ary.sort {|a,b| a.send(property).casecmp(b.send(property)) }
+        ary.sort do |a, b|
+          nil_safe_casecmp(a, b)
+        end
+      elsif ary.all? { |el| el.respond_to?(:[]) }
+        begin
+          ary.sort { |a, b| nil_safe_casecmp(a[property], b[property]) }
+        rescue TypeError
+          raise_property_error(property)
+        end
+      end
+    end
+
+    # Filter the elements of an array to those with a certain property value.
+    # By default the target is any truthy value.
+    def where(input, property, target_value = nil)
+      ary = InputIterator.new(input, context)
+
+      if ary.empty?
+        []
+      elsif ary.first.respond_to?(:[]) && target_value.nil?
+        begin
+          ary.select { |item| item[property] }
+        rescue TypeError
+          raise_property_error(property)
+        end
+      elsif ary.first.respond_to?(:[])
+        begin
+          ary.select { |item| item[property] == target_value }
+        rescue TypeError
+          raise_property_error(property)
+        end
       end
     end
 
     # Remove duplicate elements from an array
     # provide optional property with which to determine uniqueness
     def uniq(input, property = nil)
-      ary = InputIterator.new(input)
+      ary = InputIterator.new(input, context)
+
       if property.nil?
-        input.uniq
-      elsif input.first.respond_to?(:[])
-        input.uniq{ |a| a[property] }
+        ary.uniq
+      elsif ary.empty? # The next two cases assume a non-empty array.
+        []
+      elsif ary.first.respond_to?(:[])
+        begin
+          ary.uniq { |a| a[property] }
+        rescue TypeError
+          raise_property_error(property)
+        end
       end
     end
 
     # Reverse the elements of an array
     def reverse(input)
-      ary = InputIterator.new(input)
+      ary = InputIterator.new(input, context)
       ary.reverse
     end
 
     # map/collect on a given property
     def map(input, property)
-      InputIterator.new(input).map do |e|
+      InputIterator.new(input, context).map do |e|
         e = e.call if e.is_a?(Proc)
 
-        if property == "to_liquid".freeze
+        if property == "to_liquid"
           e
         elsif e.respond_to?(:[])
-          e[property]
+          r = e[property]
+          r.is_a?(Proc) ? r.call : r
+        end
+      end
+    rescue TypeError
+      raise_property_error(property)
+    end
+
+    # Remove nils within an array
+    # provide optional property with which to check for nil
+    def compact(input, property = nil)
+      ary = InputIterator.new(input, context)
+
+      if property.nil?
+        ary.compact
+      elsif ary.empty? # The next two cases assume a non-empty array.
+        []
+      elsif ary.first.respond_to?(:[])
+        begin
+          ary.reject { |a| a[property].nil? }
+        rescue TypeError
+          raise_property_error(property)
         end
       end
     end
 
     # Replace occurrences of a string with another
-    def replace(input, string, replacement = ''.freeze)
-      input.to_s.gsub(string, replacement.to_s)
+    def replace(input, string, replacement = '')
+      input.to_s.gsub(string.to_s, replacement.to_s)
     end
 
     # Replace the first occurrences of a string with another
-    def replace_first(input, string, replacement = ''.freeze)
-      input.to_s.sub(string, replacement.to_s)
+    def replace_first(input, string, replacement = '')
+      input.to_s.sub(string.to_s, replacement.to_s)
     end
 
     # remove a substring
     def remove(input, string)
-      input.to_s.gsub(string, ''.freeze)
+      input.to_s.gsub(string.to_s, '')
     end
 
     # remove the first occurrences of a substring
     def remove_first(input, string)
-      input.to_s.sub(string, ''.freeze)
+      input.to_s.sub(string.to_s, '')
     end
 
     # add one string to another
@@ -192,7 +282,10 @@ module Liquid
     end
 
     def concat(input, array)
-      InputIterator.new(input).concat(array)
+      unless array.respond_to?(:to_ary)
+        raise ArgumentError, "concat filter requires an array argument"
+      end
+      InputIterator.new(input, context).concat(array)
     end
 
     # prepend a string to another
@@ -202,7 +295,7 @@ module Liquid
 
     # Add <br /> tags in front of all newlines in input string
     def newline_to_br(input)
-      input.to_s.gsub(/\n/, "<br />\n".freeze)
+      input.to_s.gsub(/\n/, "<br />\n")
     end
 
     # Reformat a date using Ruby's core Time#strftime( string ) -> string
@@ -239,7 +332,7 @@ module Liquid
     def date(input, format)
       return input if format.to_s.empty?
 
-      return input unless date = to_date(input)
+      return input unless (date = Utils.to_date(input))
 
       date.strftime(format.to_s)
     end
@@ -262,6 +355,12 @@ module Liquid
       array.last if array.respond_to?(:last)
     end
 
+    # absolute value
+    def abs(input)
+      result = Utils.to_number(input).abs
+      result.is_a?(BigDecimal) ? result.to_f : result
+    end
+
     # addition
     def plus(input, operand)
       apply_operation(input, operand, :+)
@@ -280,79 +379,104 @@ module Liquid
     # division
     def divided_by(input, operand)
       apply_operation(input, operand, :/)
+    rescue ::ZeroDivisionError => e
+      raise Liquid::ZeroDivisionError, e.message
     end
 
     def modulo(input, operand)
       apply_operation(input, operand, :%)
+    rescue ::ZeroDivisionError => e
+      raise Liquid::ZeroDivisionError, e.message
     end
 
     def round(input, n = 0)
-      result = to_number(input).round(to_number(n))
+      result = Utils.to_number(input).round(Utils.to_number(n))
       result = result.to_f if result.is_a?(BigDecimal)
       result = result.to_i if n == 0
       result
+    rescue ::FloatDomainError => e
+      raise Liquid::FloatDomainError, e.message
     end
 
     def ceil(input)
-      to_number(input).ceil.to_i
+      Utils.to_number(input).ceil.to_i
+    rescue ::FloatDomainError => e
+      raise Liquid::FloatDomainError, e.message
     end
 
     def floor(input)
-      to_number(input).floor.to_i
+      Utils.to_number(input).floor.to_i
+    rescue ::FloatDomainError => e
+      raise Liquid::FloatDomainError, e.message
     end
 
-    def default(input, default_value = "".freeze)
-      is_blank = input.respond_to?(:empty?) ? input.empty? : !input
-      is_blank ? default_value : input
+    def at_least(input, n)
+      min_value = Utils.to_number(n)
+
+      result = Utils.to_number(input)
+      result = min_value if min_value > result
+      result.is_a?(BigDecimal) ? result.to_f : result
+    end
+
+    def at_most(input, n)
+      max_value = Utils.to_number(n)
+
+      result = Utils.to_number(input)
+      result = max_value if max_value < result
+      result.is_a?(BigDecimal) ? result.to_f : result
+    end
+
+    # Set a default value when the input is nil, false or empty
+    #
+    # Example:
+    #    {{ product.title | default: "No Title" }}
+    #
+    # Use `allow_false` when an input should only be tested against nil or empty and not false.
+    #
+    # Example:
+    #    {{ product.title | default: "No Title", allow_false: true }}
+    #
+    def default(input, default_value = '', options = {})
+      options = {} unless options.is_a?(Hash)
+      false_check = options['allow_false'] ? input.nil? : !input
+      false_check || (input.respond_to?(:empty?) && input.empty?) ? default_value : input
     end
 
     private
 
-    def to_number(obj)
-      case obj
-      when Float
-        BigDecimal.new(obj.to_s)
-      when Numeric
-        obj
-      when String
-        (obj.strip =~ /\A\d+\.\d+\z/) ? BigDecimal.new(obj) : obj.to_i
-      else
-        0
-      end
-    end
+    attr_reader :context
 
-    def to_date(obj)
-      return obj if obj.respond_to?(:strftime)
-
-      if obj.is_a?(String)
-        return nil if obj.empty?
-        obj = obj.downcase
-      end
-
-      case obj
-      when 'now'.freeze, 'today'.freeze
-        Time.now
-      when /\A\d+\z/, Integer
-        Time.at(obj.to_i)
-      when String
-        Time.parse(obj)
-      else
-        nil
-      end
-    rescue ArgumentError
-      nil
+    def raise_property_error(property)
+      raise Liquid::ArgumentError, "cannot select the property '#{property}'"
     end
 
     def apply_operation(input, operand, operation)
-      result = to_number(input).send(operation, to_number(operand))
+      result = Utils.to_number(input).send(operation, Utils.to_number(operand))
       result.is_a?(BigDecimal) ? result.to_f : result
     end
 
+    def nil_safe_compare(a, b)
+      if !a.nil? && !b.nil?
+        a <=> b
+      else
+        a.nil? ? 1 : -1
+      end
+    end
+
+    def nil_safe_casecmp(a, b)
+      if !a.nil? && !b.nil?
+        a.to_s.casecmp(b.to_s)
+      else
+        a.nil? ? 1 : -1
+      end
+    end
+
     class InputIterator
       include Enumerable
 
-      def initialize(input)
-        @input = if input.is_a?(Array)
+      def initialize(input, context)
+        @context = context
+        @input   = if input.is_a?(Array)
           input.flatten
         elsif input.is_a?(Hash)
           [input]
@@ -364,19 +488,33 @@ module Liquid
       end
 
       def join(glue)
-        to_a.join(glue)
+        to_a.join(glue.to_s)
       end
 
       def concat(args)
-        to_a.concat args
+        to_a.concat(args)
       end
 
       def reverse
         reverse_each.to_a
       end
 
+      def uniq(&block)
+        to_a.uniq(&block)
+      end
+
+      def compact
+        to_a.compact
+      end
+
+      def empty?
+        @input.each { return false }
+        true
+      end
+
       def each
         @input.each do |e|
+          e.context = @context if e.respond_to?(:context=)
           yield(e.respond_to?(:to_liquid) ? e.to_liquid : e)
         end
       end

lib/liquid/static_registers.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module Liquid
+  class StaticRegisters
+    attr_reader :static
+
+    def initialize(registers = {})
+      @static    = registers.is_a?(StaticRegisters) ? registers.static : registers
+      @registers = {}
+    end
+
+    def []=(key, value)
+      @registers[key] = value
+    end
+
+    def [](key)
+      if @registers.key?(key)
+        @registers[key]
+      else
+        @static[key]
+      end
+    end
+
+    def delete(key)
+      @registers.delete(key)
+    end
+
+    UNDEFINED = Object.new
+
+    def fetch(key, default = UNDEFINED, &block)
+      if @registers.key?(key)
+        @registers.fetch(key)
+      elsif default != UNDEFINED
+        @static.fetch(key, default, &block)
+      else
+        @static.fetch(key, &block)
+      end
+    end
+
+    def key?(key)
+      @registers.key?(key) || @static.key?(key)
+    end
+  end
+end

lib/liquid/strainer.rb

@@ -1,59 +0,0 @@
-require 'set'
-
-module Liquid
-
-  # Strainer is the parent class for the filters system.
-  # New filters are mixed into the strainer class which is then instantiated for each liquid template render run.
-  #
-  # The Strainer only allows method calls defined in filters given to it via Strainer.global_filter,
-  # Context#add_filters or Template.register_filter
-  class Strainer #:nodoc:
-    @@global_strainer = Class.new(Strainer) do
-      @filter_methods = Set.new
-    end
-    @@strainer_class_cache = Hash.new do |hash, filters|
-      hash[filters] = Class.new(@@global_strainer) do
-        @filter_methods = @@global_strainer.filter_methods.dup
-        filters.each { |f| add_filter(f) }
-      end
-    end
-
-    def initialize(context)
-      @context = context
-    end
-
-    def self.filter_methods
-      @filter_methods
-    end
-
-    def self.add_filter(filter)
-      raise ArgumentError, "Expected module but got: #{f.class}" unless filter.is_a?(Module)
-      unless self.class.include?(filter)
-        self.send(:include, filter)
-        @filter_methods.merge(filter.public_instance_methods.map(&:to_s))
-      end
-    end
-
-    def self.global_filter(filter)
-      @@global_strainer.add_filter(filter)
-    end
-
-    def self.invokable?(method)
-      @filter_methods.include?(method.to_s)
-    end
-
-    def self.create(context, filters = [])
-      @@strainer_class_cache[filters].new(context)
-    end
-
-    def invoke(method, *args)
-      if self.class.invokable?(method)
-        send(method, *args)
-      else
-        args.first
-      end
-    rescue ::ArgumentError => e
-      raise Liquid::ArgumentError.new(e.message)
-    end
-  end
-end

lib/liquid/strainer_factory.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module Liquid
+  # StrainerFactory is the factory for the filters system.
+  module StrainerFactory
+    extend self
+
+    def add_global_filter(filter)
+      strainer_class_cache.clear
+      global_filters << filter
+    end
+
+    def create(context, filters = [])
+      strainer_from_cache(filters).new(context)
+    end
+
+    private
+
+    def global_filters
+      @global_filters ||= []
+    end
+
+    def strainer_from_cache(filters)
+      strainer_class_cache[filters] ||= begin
+        klass = Class.new(StrainerTemplate)
+        global_filters.each { |f| klass.add_filter(f) }
+        filters.each { |f| klass.add_filter(f) }
+        klass
+      end
+    end
+
+    def strainer_class_cache
+      @strainer_class_cache ||= {}
+    end
+  end
+end

lib/liquid/strainer_template.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require 'set'
+
+module Liquid
+  # StrainerTemplate is the computed class for the filters system.
+  # New filters are mixed into the strainer class which is then instantiated for each liquid template render run.
+  #
+  # The Strainer only allows method calls defined in filters given to it via StrainerFactory.add_global_filter,
+  # Context#add_filters or Template.register_filter
+  class StrainerTemplate
+    def initialize(context)
+      @context = context
+    end
+
+    class << self
+      def add_filter(filter)
+        return if include?(filter)
+
+        invokable_non_public_methods = (filter.private_instance_methods + filter.protected_instance_methods).select { |m| invokable?(m) }
+        if invokable_non_public_methods.any?
+          raise MethodOverrideError, "Filter overrides registered public methods as non public: #{invokable_non_public_methods.join(', ')}"
+        end
+
+        include(filter)
+
+        filter_methods.merge(filter.public_instance_methods.map(&:to_s))
+      end
+
+      def invokable?(method)
+        filter_methods.include?(method.to_s)
+      end
+
+      private
+
+      def filter_methods
+        @filter_methods ||= Set.new
+      end
+    end
+
+    def invoke(method, *args)
+      if self.class.invokable?(method)
+        send(method, *args)
+      elsif @context.strict_filters
+        raise Liquid::UndefinedFilter, "undefined filter #{method}"
+      else
+        args.first
+      end
+    rescue ::ArgumentError => e
+      raise Liquid::ArgumentError, e.message, e.backtrace
+    end
+  end
+end

lib/liquid/tablerowloop_drop.rb

@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+module Liquid
+  class TablerowloopDrop < Drop
+    def initialize(length, cols)
+      @length = length
+      @row    = 1
+      @col    = 1
+      @cols   = cols
+      @index  = 0
+    end
+
+    attr_reader :length, :col, :row
+
+    def index
+      @index + 1
+    end
+
+    def index0
+      @index
+    end
+
+    def col0
+      @col - 1
+    end
+
+    def rindex
+      @length - @index
+    end
+
+    def rindex0
+      @length - @index - 1
+    end
+
+    def first
+      @index == 0
+    end
+
+    def last
+      @index == @length - 1
+    end
+
+    def col_first
+      @col == 1
+    end
+
+    def col_last
+      @col == @cols
+    end
+
+    protected
+
+    def increment!
+      @index += 1
+
+      if @col == @cols
+        @col = 1
+        @row += 1
+      else
+        @col += 1
+      end
+    end
+  end
+end

lib/liquid/tag.rb

@@ -1,49 +1,65 @@
+# frozen_string_literal: true
+
 module Liquid
   class Tag
-    attr_accessor :options, :line_number
-    attr_reader :nodelist, :warnings
+    attr_reader :nodelist, :tag_name, :line_number, :parse_context
+    alias_method :options, :parse_context
     include ParserSwitching
 
     class << self
-      def parse(tag_name, markup, tokens, options)
-        tag = new(tag_name, markup, options)
-        tag.parse(tokens)
+      def parse(tag_name, markup, tokenizer, parse_context)
+        tag = new(tag_name, markup, parse_context)
+        tag.parse(tokenizer)
         tag
       end
 
+      def disable_tags(*tag_names)
+        @disabled_tags ||= []
+        @disabled_tags.concat(tag_names)
+        prepend(Disabler)
+      end
+
       private :new
     end
 
-    def initialize(tag_name, markup, options)
-      @tag_name   = tag_name
-      @markup     = markup
-      @options    = options
+    def initialize(tag_name, markup, parse_context)
+      @tag_name      = tag_name
+      @markup        = markup
+      @parse_context = parse_context
+      @line_number   = parse_context.line_number
     end
 
-    def parse(tokens)
+    def parse(_tokens)
     end
 
     def raw
-      tag = @tag_name.strip
-      markup = @markup.strip
-      tag << " #{markup}" unless markup.empty?
-      tag
+      "#{@tag_name} #{@markup}"
     end
 
     def name
       self.class.name.downcase
     end
 
-    def render(context)
-      ''.freeze
+    def render(_context)
+      ''
+    end
+
+    # For backwards compatibility with custom tags. In a future release, the semantics
+    # of the `render_to_output_buffer` method will become the default and the `render`
+    # method will be removed.
+    def render_to_output_buffer(context, output)
+      output << render(context)
+      output
     end
 
     def blank?
       false
     end
 
-    def format
-      "{% #{raw} %}"
+    private
+
+    def parse_expression(markup)
+      parse_context.parse_expression(markup)
     end
   end
 end

lib/liquid/tag/disableable.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Tag
+    module Disableable
+      def render_to_output_buffer(context, output)
+        if context.tag_disabled?(tag_name)
+          output << disabled_error(context)
+          return
+        end
+        super
+      end
+
+      def disabled_error(context)
+        # raise then rescue the exception so that the Context#exception_renderer can re-raise it
+        raise DisabledError, "#{tag_name} #{parse_context[:locale].t('errors.disabled.tag')}"
+      rescue DisabledError => exc
+        context.handle_error(exc, line_number)
+      end
+    end
+  end
+end

lib/liquid/tag/disabler.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Tag
+    module Disabler
+      module ClassMethods
+        attr_reader :disabled_tags
+      end
+
+      def self.prepended(base)
+        base.extend(ClassMethods)
+      end
+
+      def render_to_output_buffer(context, output)
+        context.with_disabled_tags(self.class.disabled_tags) do
+          super
+        end
+      end
+    end
+  end
+end

lib/liquid/tags/assign.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Assign sets a variable in your template.
   #
   #   {% assign foo = 'monkey' %}
@@ -11,35 +12,62 @@ module Liquid
   class Assign < Tag
     Syntax = /(#{VariableSignature}+)\s*=\s*(.*)\s*/om
 
-    def initialize(tag_name, markup, options)
+    # @api private
+    def self.raise_syntax_error(parse_context)
+      raise Liquid::SyntaxError, parse_context.locale.t('errors.syntax.assign')
+    end
+
+    attr_reader :to, :from
+
+    def initialize(tag_name, markup, parse_context)
       super
       if markup =~ Syntax
-        @to = $1
-        @from = Variable.new($2,options)
-        @from.line_number = line_number
+        @to   = Regexp.last_match(1)
+        @from = Variable.new(Regexp.last_match(2), parse_context)
       else
-        raise SyntaxError.new options[:locale].t("errors.syntax.assign".freeze)
+        self.class.raise_syntax_error(parse_context)
       end
     end
 
-    def render(context)
+    def render_to_output_buffer(context, output)
       val = @from.render(context)
       context.scopes.last[@to] = val
-
-      inc = val.instance_of?(String) || val.instance_of?(Array) || val.instance_of?(Hash) ? val.length : 1
-      context.resource_limits.assign_score += inc
-
-      ''.freeze
+      context.resource_limits.increment_assign_score(assign_score_of(val))
+      output
     end
 
     def blank?
       true
     end
 
-    def format
-      "{% assign #{@to} = #{@from.format} %}"
+    private
+
+    def assign_score_of(val)
+      if val.instance_of?(String)
+        val.bytesize
+      elsif val.instance_of?(Array)
+        sum = 1
+        # Uses #each to avoid extra allocations.
+        val.each { |child| sum += assign_score_of(child) }
+        sum
+      elsif val.instance_of?(Hash)
+        sum = 1
+        val.each do |key, entry_value|
+          sum += assign_score_of(key)
+          sum += assign_score_of(entry_value)
+        end
+        sum
+      else
+        1
+      end
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [@node.from]
+      end
     end
   end
 
-  Template.register_tag('assign'.freeze, Assign)
+  Template.register_tag('assign', Assign)
 end

lib/liquid/tags/break.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Break tag to be used to break out of a for loop.
   #
   # == Basic Usage:
@@ -10,12 +11,13 @@ module Liquid
   #    {% endfor %}
   #
   class Break < Tag
+    INTERRUPT = BreakInterrupt.new.freeze
 
-    def interrupt
-      BreakInterrupt.new
+    def render_to_output_buffer(context, output)
+      context.push_interrupt(INTERRUPT)
+      output
     end
-
   end
 
-  Template.register_tag('break'.freeze, Break)
+  Template.register_tag('break', Break)
 end

lib/liquid/tags/capture.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # Capture stores the result of a block into a variable without rendering it inplace.
   #
@@ -16,27 +18,24 @@ module Liquid
     def initialize(tag_name, markup, options)
       super
       if markup =~ Syntax
-        @to = $1
+        @to = Regexp.last_match(1)
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.capture"))
+        raise SyntaxError, options[:locale].t("errors.syntax.capture")
       end
     end
 
-    def render(context)
-      output = super
-      context.scopes.last[@to] = output
-      context.resource_limits.assign_score += output.length
-      ''.freeze
+    def render_to_output_buffer(context, output)
+      context.resource_limits.with_capture do
+        capture_output = render(context)
+        context.scopes.last[@to] = capture_output
+      end
+      output
     end
 
     def blank?
       true
     end
-
-    def format
-      "{% #{block_name} #{@to} %}#{@body.format}{% #{block_delimiter} %}"
-    end
   end
 
-  Template.register_tag('capture'.freeze, Capture)
+  Template.register_tag('capture', Capture)
 end

lib/liquid/tags/case.rb

@@ -1,24 +1,34 @@
+# frozen_string_literal: true
+
 module Liquid
   class Case < Block
     Syntax     = /(#{QuotedFragment})/o
     WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/om
 
+    attr_reader :blocks, :left
+
     def initialize(tag_name, markup, options)
       super
       @blocks = []
 
       if markup =~ Syntax
-        @left = Expression.parse($1)
+        @left = parse_expression(Regexp.last_match(1))
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.case".freeze))
+        raise SyntaxError, options[:locale].t("errors.syntax.case")
       end
     end
 
     def parse(tokens)
-      @initial_body = body = BlockBody.new
-      while more = parse_body(body, tokens)
-        body = @blocks.last.attachment
+      body = case_body = new_body
+      body = @blocks.last.attachment while parse_body(body, tokens)
+      @blocks.reverse_each do |condition|
+        body = condition.attachment
+        unless body.frozen?
+          body.remove_blank_strings if blank?
+          body.freeze
+        end
       end
+      case_body.freeze
     end
 
     def nodelist
@@ -27,75 +37,64 @@ module Liquid
 
     def unknown_tag(tag, markup, tokens)
       case tag
-      when 'when'.freeze
+      when 'when'
         record_when_condition(markup)
-      when 'else'.freeze
+      when 'else'
         record_else_condition(markup)
       else
         super
       end
     end
 
-    def render(context)
-      context.stack do
-        execute_else_block = true
-
-        output = ''
-        @blocks.each do |block|
-          if block.else?
-            return block.attachment.render(context) if execute_else_block
-          elsif block.evaluate(context)
-            execute_else_block = false
-            output << block.attachment.render(context)
-          end
-        end
-        output
-      end
-    end
-
-    def format
-      out = "{% case #{Expression.format(@left)} %}#{@initial_body.format}"
+    def render_to_output_buffer(context, output)
+      execute_else_block = true
 
       @blocks.each do |block|
         if block.else?
-          out << "{% else %}"
-        else
-          out << "{% when #{Expression.format(block.right)} %}"
+          block.attachment.render_to_output_buffer(context, output) if execute_else_block
+        elsif block.evaluate(context)
+          execute_else_block = false
+          block.attachment.render_to_output_buffer(context, output)
         end
-        out << block.attachment.format
       end
 
-      out + "{% endcase %}"
+      output
     end
 
     private
 
     def record_when_condition(markup)
-      body = BlockBody.new
+      body = new_body
 
       while markup
-        if not markup =~ WhenSyntax
-          raise SyntaxError.new(options[:locale].t("errors.syntax.case_invalid_when".freeze))
+        unless markup =~ WhenSyntax
+          raise SyntaxError, options[:locale].t("errors.syntax.case_invalid_when")
         end
 
-        markup = $2
+        markup = Regexp.last_match(2)
 
-        block = Condition.new(@left, '=='.freeze, Expression.parse($1))
+        block = Condition.new(@left, '==', Condition.parse_expression(parse_context, Regexp.last_match(1)))
         block.attach(body)
         @blocks << block
       end
     end
 
     def record_else_condition(markup)
-      if not markup.strip.empty?
-        raise SyntaxError.new(options[:locale].t("errors.syntax.case_invalid_else".freeze))
+      unless markup.strip.empty?
+        raise SyntaxError, options[:locale].t("errors.syntax.case_invalid_else")
       end
 
       block = ElseCondition.new
-      block.attach(BlockBody.new)
+      block.attach(new_body)
       @blocks << block
     end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [@node.left] + @node.blocks
+      end
+    end
   end
 
-  Template.register_tag('case'.freeze, Case)
+  Template.register_tag('case', Case)
 end

lib/liquid/tags/comment.rb

@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 module Liquid
   class Comment < Block
-    def render(context)
-      ''.freeze
+    def render_to_output_buffer(_context, output)
+      output
     end
 
-    def unknown_tag(tag, markup, tokens)
+    def unknown_tag(_tag, _markup, _tokens)
     end
 
     def blank?
@@ -12,5 +14,5 @@ module Liquid
     end
   end
 
-  Template.register_tag('comment'.freeze, Comment)
+  Template.register_tag('comment', Comment)
 end

lib/liquid/tags/continue.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # Continue tag to be used to break out of a for loop.
   #
@@ -9,10 +11,13 @@ module Liquid
   #    {% endfor %}
   #
   class Continue < Tag
-    def interrupt
-      ContinueInterrupt.new
+    INTERRUPT = ContinueInterrupt.new.freeze
+
+    def render_to_output_buffer(context, output)
+      context.push_interrupt(INTERRUPT)
+      output
     end
   end
 
-  Template.register_tag('continue'.freeze, Continue)
+  Template.register_tag('continue', Continue)
 end

lib/liquid/tags/cycle.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # Cycle is usually used within a loop to alternate between values, like colors or DOM classes.
   #
@@ -15,42 +17,43 @@ module Liquid
     SimpleSyntax = /\A#{QuotedFragment}+/o
     NamedSyntax  = /\A(#{QuotedFragment})\s*\:\s*(.*)/om
 
+    attr_reader :variables
+
     def initialize(tag_name, markup, options)
       super
       case markup
       when NamedSyntax
-        @variables = variables_from_string($2)
-        @name = Expression.parse($1)
-        @named = true
+        @variables = variables_from_string(Regexp.last_match(2))
+        @name      = parse_expression(Regexp.last_match(1))
       when SimpleSyntax
         @variables = variables_from_string(markup)
-        @name = @variables.to_s
+        @name      = @variables.to_s
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.cycle".freeze))
+        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
       end
     end
 
-    def render(context)
-      context.registers[:cycle] ||= Hash.new(0)
+    def render_to_output_buffer(context, output)
+      context.registers[:cycle] ||= {}
 
-      context.stack do
-        key = context.evaluate(@name)
-        iteration = context.registers[:cycle][key]
-        result = context.evaluate(@variables[iteration])
-        iteration += 1
-        iteration  = 0  if iteration >= @variables.size
-        context.registers[:cycle][key] = iteration
-        result
-      end
-    end
+      key       = context.evaluate(@name)
+      iteration = context.registers[:cycle][key].to_i
 
-    def format
-      formatted_vars = @variables.map { |v| Expression.format(v) }.join(', ')
-      if @named
-        "{% cycle #{Expression.format(@name)}: #{formatted_vars} %}"
-      else
-        "{% cycle #{formatted_vars} %}"
+      val = context.evaluate(@variables[iteration])
+
+      if val.is_a?(Array)
+        val = val.join
+      elsif !val.is_a?(String)
+        val = val.to_s
       end
+
+      output << val
+
+      iteration += 1
+      iteration = 0 if iteration >= @variables.size
+
+      context.registers[:cycle][key] = iteration
+      output
     end
 
     private
@@ -58,9 +61,15 @@ module Liquid
     def variables_from_string(markup)
       markup.split(',').collect do |var|
         var =~ /\s*(#{QuotedFragment})\s*/o
-        $1 ? Expression.parse($1) : nil
+        Regexp.last_match(1) ? parse_expression(Regexp.last_match(1)) : nil
       end.compact
     end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        Array(@node.variables)
+      end
+    end
   end
 
   Template.register_tag('cycle', Cycle)

lib/liquid/tags/decrement.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # decrement is used in a place where one needs to insert a counter
   #     into a template, and needs the counter to survive across
   #     multiple instantiations of the template.
@@ -24,15 +25,14 @@ module Liquid
       @variable = markup.strip
     end
 
-    def render(context)
+    def render_to_output_buffer(context, output)
       value = context.environments.first[@variable] ||= 0
-      value = value - 1
+      value -= 1
       context.environments.first[@variable] = value
-      value.to_s
+      output << value.to_s
+      output
     end
-
-    private
   end
 
-  Template.register_tag('decrement'.freeze, Decrement)
+  Template.register_tag('decrement', Decrement)
 end

lib/liquid/tags/echo.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module Liquid
+  # Echo outputs an expression
+  #
+  #   {% echo monkey %}
+  #   {% echo user.name %}
+  #
+  # This is identical to variable output syntax, like {{ foo }}, but works
+  # inside {% liquid %} tags. The full syntax is supported, including filters:
+  #
+  #   {% echo user | link %}
+  #
+  class Echo < Tag
+    def initialize(tag_name, markup, parse_context)
+      super
+      @variable = Variable.new(markup, parse_context)
+    end
+
+    def render(context)
+      @variable.render_to_output_buffer(context, +'')
+    end
+  end
+
+  Template.register_tag('echo', Echo)
+end

lib/liquid/tags/for.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # "For" iterates over an array or collection.
   # Several useful variables are available to you within the loop.
   #
@@ -24,7 +25,7 @@ module Liquid
   #      {{ item.name }}
   #    {% end %}
   #
-  #  To reverse the for loop simply use {% for item in collection reversed %}
+  #  To reverse the for loop simply use {% for item in collection reversed %} (note that the flag's spelling is different to the filter `reverse`)
   #
   # == Available variables:
   #
@@ -47,16 +48,26 @@ module Liquid
   class For < Block
     Syntax = /\A(#{VariableSegment}+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
 
+    attr_reader :collection_name, :variable_name, :limit, :from
+
     def initialize(tag_name, markup, options)
       super
+      @from = @limit = nil
       parse_with_selected_parser(markup)
-      @for_block = BlockBody.new
+      @for_block = new_body
+      @else_block = nil
     end
 
     def parse(tokens)
-      if more = parse_body(@for_block, tokens)
+      if parse_body(@for_block, tokens)
         parse_body(@else_block, tokens)
       end
+      if blank?
+        @else_block&.remove_blank_strings
+        @for_block.remove_blank_strings
+      end
+      @else_block&.freeze
+      @for_block.freeze
     end
 
     def nodelist
@@ -64,115 +75,53 @@ module Liquid
     end
 
     def unknown_tag(tag, markup, tokens)
-      return super unless tag == 'else'.freeze
-      @else_block = BlockBody.new
+      return super unless tag == 'else'
+      @else_block = new_body
     end
 
-    def render(context)
-      context.registers[:for] ||= Hash.new(0)
+    def render_to_output_buffer(context, output)
+      segment = collection_segment(context)
 
-      collection = context.evaluate(@collection_name)
-      collection = collection.to_a if collection.is_a?(Range)
-
-      # Maintains Ruby 1.8.7 String#each behaviour on 1.9
-      return render_else(context) unless iterable?(collection)
-
-      from = if @from == :continue
-        context.registers[:for][@name].to_i
+      if segment.empty?
+        render_else(context, output)
       else
-        context.evaluate(@from).to_i
+        render_segment(context, output, segment)
       end
 
-      limit = context.evaluate(@limit)
-      to    = limit ? limit.to_i + from : nil
-
-      segment = Utils.slice_collection(collection, from, to)
-
-      return render_else(context) if segment.empty?
-
-      segment.reverse! if @reversed
-
-      result = ''
-
-      length = segment.length
-
-      # Store our progress through the collection for the continue flag
-      context.registers[:for][@name] = from + segment.length
-
-      parent_loop = context['forloop'.freeze]
-
-      context.stack do
-        segment.each_with_index do |item, index|
-          context[@variable_name] = item
-          context['forloop'.freeze] = {
-            'name'.freeze       => @name,
-            'length'.freeze     => length,
-            'index'.freeze      => index + 1,
-            'index0'.freeze     => index,
-            'rindex'.freeze     => length - index,
-            'rindex0'.freeze    => length - index - 1,
-            'first'.freeze      => (index == 0),
-            'last'.freeze       => (index == length - 1),
-            'parentloop'.freeze => parent_loop
-          }
-
-          result << @for_block.render(context)
-
-          # Handle any interrupts if they exist.
-          if context.has_interrupt?
-            interrupt = context.pop_interrupt
-            break if interrupt.is_a? BreakInterrupt
-            next if interrupt.is_a? ContinueInterrupt
-          end
-        end
-      end
-      result
-    end
-
-    def format
-      args = [Expression.format(@collection_name)]
-      args << "reversed" if @reversed
-      args << "limit: #{Expression.format(@limit)}" if @limit
-      args << "offset: " << (@from == :continue ? 'continue' : Expression.format(@from)) if @from
-
-      out = "{% for #{@variable_name} in #{args.join(' ')} %}"
-      out << @for_block.format
-      if @else_block
-        out << "{% else %}"
-        out << @else_block.format
-      end
-      out + "{% endfor %}"
+      output
     end
 
     protected
 
     def lax_parse(markup)
       if markup =~ Syntax
-        @variable_name = $1
-        collection_name = $2
-        @reversed = $3
-        @name = "#{@variable_name}-#{collection_name}"
-        @collection_name = Expression.parse(collection_name)
+        @variable_name   = Regexp.last_match(1)
+        collection_name  = Regexp.last_match(2)
+        @reversed        = !!Regexp.last_match(3)
+        @name            = "#{@variable_name}-#{collection_name}"
+        @collection_name = parse_expression(collection_name)
         markup.scan(TagAttributes) do |key, value|
           set_attribute(key, value)
         end
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.for".freeze))
+        raise SyntaxError, options[:locale].t("errors.syntax.for")
       end
     end
 
     def strict_parse(markup)
       p = Parser.new(markup)
       @variable_name = p.consume(:id)
-      raise SyntaxError.new(options[:locale].t("errors.syntax.for_invalid_in".freeze))  unless p.id?('in'.freeze)
-      collection_name = p.expression
-      @name = "#{@variable_name}-#{collection_name}"
-      @collection_name = Expression.parse(collection_name)
-      @reversed = p.id?('reversed'.freeze)
+      raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_in") unless p.id?('in')
+
+      collection_name  = p.expression
+      @collection_name = parse_expression(collection_name)
+
+      @name     = "#{@variable_name}-#{collection_name}"
+      @reversed = p.id?('reversed')
 
       while p.look(:id) && p.look(:colon, 1)
-        unless attribute = p.id?('limit'.freeze) || p.id?('offset'.freeze)
-          raise SyntaxError.new(options[:locale].t("errors.syntax.for_invalid_attribute".freeze))
+        unless (attribute = p.id?('limit') || p.id?('offset'))
+          raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_attribute")
         end
         p.consume
         set_attribute(attribute, p.expression)
@@ -182,27 +131,97 @@ module Liquid
 
     private
 
+    def collection_segment(context)
+      offsets = context.registers[:for] ||= {}
+
+      from = if @from == :continue
+        offsets[@name].to_i
+      else
+        from_value = context.evaluate(@from)
+        if from_value.nil?
+          0
+        else
+          Utils.to_integer(from_value)
+        end
+      end
+
+      collection = context.evaluate(@collection_name)
+      collection = collection.to_a if collection.is_a?(Range)
+
+      limit_value = context.evaluate(@limit)
+      to = if limit_value.nil?
+        nil
+      else
+        Utils.to_integer(limit_value) + from
+      end
+
+      segment = Utils.slice_collection(collection, from, to)
+      segment.reverse! if @reversed
+
+      offsets[@name] = from + segment.length
+
+      segment
+    end
+
+    def render_segment(context, output, segment)
+      for_stack = context.registers[:for_stack] ||= []
+      length    = segment.length
+
+      context.stack do
+        loop_vars = Liquid::ForloopDrop.new(@name, length, for_stack[-1])
+
+        for_stack.push(loop_vars)
+
+        begin
+          context['forloop'] = loop_vars
+
+          segment.each do |item|
+            context[@variable_name] = item
+            @for_block.render_to_output_buffer(context, output)
+            loop_vars.send(:increment!)
+
+            # Handle any interrupts if they exist.
+            next unless context.interrupt?
+            interrupt = context.pop_interrupt
+            break if interrupt.is_a?(BreakInterrupt)
+            next if interrupt.is_a?(ContinueInterrupt)
+          end
+        ensure
+          for_stack.pop
+        end
+      end
+
+      output
+    end
+
     def set_attribute(key, expr)
       case key
-      when 'offset'.freeze
-        @from = if expr == 'continue'.freeze
+      when 'offset'
+        @from = if expr == 'continue'
+          Usage.increment('for_offset_continue')
           :continue
         else
-          Expression.parse(expr)
+          parse_expression(expr)
         end
-      when 'limit'.freeze
-        @limit = Expression.parse(expr)
+      when 'limit'
+        @limit = parse_expression(expr)
       end
     end
 
-    def render_else(context)
-      @else_block ? @else_block.render(context) : ''.freeze
+    def render_else(context, output)
+      if @else_block
+        @else_block.render_to_output_buffer(context, output)
+      else
+        output
+      end
     end
 
-    def iterable?(collection)
-      collection.respond_to?(:each) || Utils.non_blank_string?(collection)
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        (super + [@node.limit, @node.from, @node.collection_name]).compact
+      end
     end
   end
 
-  Template.register_tag('for'.freeze, For)
+  Template.register_tag('for', For)
 end

lib/liquid/tags/if.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # If is the conditional block
   #
@@ -10,121 +12,123 @@ module Liquid
   #    There are {% if count < 5 %} less {% else %} more {% endif %} items than you need.
   #
   class If < Block
-    Syntax = /(#{QuotedFragment})\s*([=!<>a-z_]+)?\s*(#{QuotedFragment})?/o
+    Syntax                  = /(#{QuotedFragment})\s*([=!<>a-z_]+)?\s*(#{QuotedFragment})?/o
     ExpressionsAndOperators = /(?:\b(?:\s?and\s?|\s?or\s?)\b|(?:\s*(?!\b(?:\s?and\s?|\s?or\s?)\b)(?:#{QuotedFragment}|\S+)\s*)+)/o
-    BOOLEAN_OPERATORS = %w(and or)
+    BOOLEAN_OPERATORS       = %w(and or).freeze
+
+    attr_reader :blocks
 
     def initialize(tag_name, markup, options)
       super
       @blocks = []
-      push_block('if'.freeze, markup)
-    end
-
-    def parse(tokens)
-      while more = parse_body(@blocks.last.attachment, tokens)
-      end
+      push_block('if', markup)
     end
 
     def nodelist
       @blocks.map(&:attachment)
     end
 
+    def parse(tokens)
+      while parse_body(@blocks.last.attachment, tokens)
+      end
+      @blocks.reverse_each do |block|
+        block.attachment.remove_blank_strings if blank?
+        block.attachment.freeze
+      end
+    end
+
+    ELSE_TAG_NAMES = ['elsif', 'else'].freeze
+    private_constant :ELSE_TAG_NAMES
+
     def unknown_tag(tag, markup, tokens)
-      if ['elsif'.freeze, 'else'.freeze].include?(tag)
+      if ELSE_TAG_NAMES.include?(tag)
         push_block(tag, markup)
       else
         super
       end
     end
 
-    def render(context)
-      context.stack do
-        @blocks.each do |block|
-          if block.evaluate(context)
-            return block.attachment.render(context)
-          end
-        end
-        ''.freeze
-      end
-    end
-
-    def format
-      out = ""
-      first_condition = true
-
+    def render_to_output_buffer(context, output)
       @blocks.each do |block|
-        if block.else?
-          out << "{% else %}"
-        elsif first_condition
-          out << "{% #{block_name} #{block.format} %}"
-          first_condition = false
-        else
-          out << "{% elsif #{block.format} %}"
+        if block.evaluate(context)
+          return block.attachment.render_to_output_buffer(context, output)
         end
-        out << block.attachment.format
       end
 
-      out + "{% #{block_delimiter} %}"
+      output
     end
 
     private
 
-      def push_block(tag, markup)
-        block = if tag == 'else'.freeze
-          ElseCondition.new
-        else
-          parse_with_selected_parser(markup)
-        end
-
-        @blocks.push(block)
-        block.attach(BlockBody.new)
+    def push_block(tag, markup)
+      block = if tag == 'else'
+        ElseCondition.new
+      else
+        parse_with_selected_parser(markup)
       end
 
-      def lax_parse(markup)
-        expressions = markup.scan(ExpressionsAndOperators)
-        raise(SyntaxError.new(options[:locale].t("errors.syntax.if".freeze))) unless expressions.pop =~ Syntax
+      @blocks.push(block)
+      block.attach(new_body)
+    end
 
-        condition = Condition.new(Expression.parse($1), $2, Expression.parse($3))
+    def parse_expression(markup)
+      Condition.parse_expression(parse_context, markup)
+    end
 
-        while not expressions.empty?
-          operator = expressions.pop.to_s.strip
+    def lax_parse(markup)
+      expressions = markup.scan(ExpressionsAndOperators)
+      raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop =~ Syntax
 
-          raise(SyntaxError.new(options[:locale].t("errors.syntax.if".freeze))) unless expressions.pop.to_s =~ Syntax
+      condition = Condition.new(parse_expression(Regexp.last_match(1)), Regexp.last_match(2), parse_expression(Regexp.last_match(3)))
 
-          new_condition = Condition.new(Expression.parse($1), $2, Expression.parse($3))
-          raise(SyntaxError.new(options[:locale].t("errors.syntax.if".freeze))) unless BOOLEAN_OPERATORS.include?(operator)
-          new_condition.send(operator, condition)
-          condition = new_condition
-        end
+      until expressions.empty?
+        operator = expressions.pop.to_s.strip
 
-        condition
+        raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop.to_s =~ Syntax
+
+        new_condition = Condition.new(parse_expression(Regexp.last_match(1)), Regexp.last_match(2), parse_expression(Regexp.last_match(3)))
+        raise SyntaxError, options[:locale].t("errors.syntax.if") unless BOOLEAN_OPERATORS.include?(operator)
+        new_condition.send(operator, condition)
+        condition = new_condition
       end
 
-      def strict_parse(markup)
-        p = Parser.new(markup)
+      condition
+    end
 
-        condition = parse_comparison(p)
+    def strict_parse(markup)
+      p = Parser.new(markup)
+      condition = parse_binary_comparisons(p)
+      p.consume(:end_of_string)
+      condition
+    end
 
-        while op = (p.id?('and'.freeze) || p.id?('or'.freeze))
-          new_cond = parse_comparison(p)
-          new_cond.send(op, condition)
-          condition = new_cond
-        end
-        p.consume(:end_of_string)
-
-        condition
+    def parse_binary_comparisons(p)
+      condition = parse_comparison(p)
+      first_condition = condition
+      while (op = (p.id?('and') || p.id?('or')))
+        child_condition = parse_comparison(p)
+        condition.send(op, child_condition)
+        condition = child_condition
       end
+      first_condition
+    end
 
-      def parse_comparison(p)
-        a = Expression.parse(p.expression)
-        if op = p.consume?(:comparison)
-          b = Expression.parse(p.expression)
-          Condition.new(a, op, b)
-        else
-          Condition.new(a)
-        end
+    def parse_comparison(p)
+      a = parse_expression(p.expression)
+      if (op = p.consume?(:comparison))
+        b = parse_expression(p.expression)
+        Condition.new(a, op, b)
+      else
+        Condition.new(a)
       end
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        @node.blocks
+      end
+    end
   end
 
-  Template.register_tag('if'.freeze, If)
+  Template.register_tag('if', If)
 end

lib/liquid/tags/ifchanged.rb

@@ -1,20 +1,19 @@
+# frozen_string_literal: true
+
 module Liquid
   class Ifchanged < Block
+    def render_to_output_buffer(context, output)
+      block_output = +''
+      super(context, block_output)
 
-    def render(context)
-      context.stack do
-
-        output = super
-
-        if output != context.registers[:ifchanged]
-          context.registers[:ifchanged] = output
-          output
-        else
-          ''.freeze
-        end
+      if block_output != context.registers[:ifchanged]
+        context.registers[:ifchanged] = block_output
+        output << block_output
       end
+
+      output
     end
   end
 
-  Template.register_tag('ifchanged'.freeze, Ifchanged)
+  Template.register_tag('ifchanged', Ifchanged)
 end

lib/liquid/tags/include.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Include allows templates to relate with other templates
   #
   # Simply include another template:
@@ -15,107 +16,96 @@ module Liquid
   #   {% include 'product' for products %}
   #
   class Include < Tag
-    Syntax = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?/o
+    prepend Tag::Disableable
+
+    SYNTAX = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
+    Syntax = SYNTAX
+
+    attr_reader :template_name_expr, :variable_name_expr, :attributes
 
     def initialize(tag_name, markup, options)
       super
 
-      if markup =~ Syntax
+      if markup =~ SYNTAX
 
-        template_name = $1
-        variable_name = $3
+        template_name = Regexp.last_match(1)
+        variable_name = Regexp.last_match(3)
 
-        @variable_name_expr = variable_name ? Expression.parse(variable_name) : nil
-        @template_name_expr = Expression.parse(template_name)
-        @attributes = {}
+        @alias_name         = Regexp.last_match(5)
+        @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
+        @template_name_expr = parse_expression(template_name)
+        @attributes         = {}
 
         markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = Expression.parse(value)
+          @attributes[key] = parse_expression(value)
         end
 
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.include".freeze))
+        raise SyntaxError, options[:locale].t("errors.syntax.include")
       end
     end
 
-    def parse(tokens)
+    def parse(_tokens)
     end
 
-    def render(context)
-      partial = load_cached_partial(context)
-
+    def render_to_output_buffer(context, output)
       template_name = context.evaluate(@template_name_expr)
-      context_variable_name = template_name.split('/'.freeze).last
+      raise ArgumentError, options[:locale].t("errors.argument.include") unless template_name
+
+      partial = PartialCache.load(
+        template_name,
+        context: context,
+        parse_context: parse_context
+      )
+
+      context_variable_name = @alias_name || template_name.split('/').last
 
       variable = if @variable_name_expr
         context.evaluate(@variable_name_expr)
       else
-        context.find_variable(template_name)
+        context.find_variable(template_name, raise_on_not_found: false)
       end
 
-      context.stack do
-        @attributes.each do |key, value|
-          context[key] = context.evaluate(value)
-        end
-
-        if variable.is_a?(Array)
-          variable.collect do |var|
-            context[context_variable_name] = var
-            partial.render(context)
+      old_template_name = context.template_name
+      old_partial       = context.partial
+      begin
+        context.template_name = template_name
+        context.partial       = true
+        context.stack do
+          @attributes.each do |key, value|
+            context[key] = context.evaluate(value)
+          end
+
+          if variable.is_a?(Array)
+            variable.each do |var|
+              context[context_variable_name] = var
+              partial.render_to_output_buffer(context, output)
+            end
+          else
+            context[context_variable_name] = variable
+            partial.render_to_output_buffer(context, output)
           end
-        else
-          context[context_variable_name] = variable
-          partial.render(context)
         end
+      ensure
+        context.template_name = old_template_name
+        context.partial       = old_partial
       end
+
+      output
     end
 
-    def format
-      segments = [@tag_name, Expression.format(@template_name_expr)]
+    alias_method :parse_context, :options
+    private :parse_context
 
-      if @variable_name_expr
-        segments << "with"
-        segments << Expression.format(@variable_name_expr)
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.template_name_expr,
+          @node.variable_name_expr,
+        ] + @node.attributes.values
       end
-
-      unless @attributes.empty?
-        segments << @attributes.map { |k, v| "#{k}: #{Expression.format(v)}" }.join(", ")
-      end
-
-      "{% #{segments.join(' ')} %}"
     end
-
-    private
-      def load_cached_partial(context)
-        cached_partials = context.registers[:cached_partials] || {}
-        template_name = context.evaluate(@template_name_expr)
-
-        if cached = cached_partials[template_name]
-          return cached
-        end
-        source = read_template_from_file_system(context)
-        partial = Liquid::Template.parse(source, pass_options)
-        cached_partials[template_name] = partial
-        context.registers[:cached_partials] = cached_partials
-        partial
-      end
-
-      def read_template_from_file_system(context)
-        file_system = context.registers[:file_system] || Liquid::Template.file_system
-
-        file_system.read_template_file(context.evaluate(@template_name_expr))
-      end
-
-      def pass_options
-        dont_pass = @options[:include_options_blacklist]
-        return {locale: @options[:locale]} if dont_pass == true
-        opts = @options.merge(included: true, include_options_blacklist: false)
-        if dont_pass.is_a?(Array)
-          dont_pass.each {|o| opts.delete(o)}
-        end
-        opts
-      end
   end
 
-  Template.register_tag('include'.freeze, Include)
+  Template.register_tag('include', Include)
 end

lib/liquid/tags/increment.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # increment is used in a place where one needs to insert a counter
   #     into a template, and needs the counter to survive across
@@ -20,12 +22,14 @@ module Liquid
       @variable = markup.strip
     end
 
-    def render(context)
+    def render_to_output_buffer(context, output)
       value = context.environments.first[@variable] ||= 0
       context.environments.first[@variable] = value + 1
-      value.to_s
+
+      output << value.to_s
+      output
     end
   end
 
-  Template.register_tag('increment'.freeze, Increment)
+  Template.register_tag('increment', Increment)
 end

lib/liquid/tags/inline_comment.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module Liquid
+  class InlineComment < Tag
+    def blank?
+      true
+    end
+
+    def render_to_output_buffer(_context, _output)
+    end
+  end
+
+  Template.register_tag('--', InlineComment)
+end
+

lib/liquid/tags/raw.rb

@@ -1,20 +1,32 @@
+# frozen_string_literal: true
+
 module Liquid
   class Raw < Block
+    Syntax = /\A\s*\z/
     FullTokenPossiblyInvalid = /\A(.*)#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}\z/om
 
-    def parse(tokens)
-      @body = ''
-      while token = tokens.shift
-        if token =~ FullTokenPossiblyInvalid
-          @body << $1 if $1 != "".freeze
-          return if block_delimiter == $2
-        end
-        @body << token if not token.empty?
-      end
+    def initialize(tag_name, markup, parse_context)
+      super
+
+      ensure_valid_markup(tag_name, markup, parse_context)
     end
 
-    def render(context)
-      @body
+    def parse(tokens)
+      @body = +''
+      while (token = tokens.shift)
+        if token =~ FullTokenPossiblyInvalid && block_delimiter == Regexp.last_match(2)
+          @body << Regexp.last_match(1) if Regexp.last_match(1) != ""
+          return
+        end
+        @body << token unless token.empty?
+      end
+
+      raise_tag_never_closed(block_name)
+    end
+
+    def render_to_output_buffer(_context, output)
+      output << @body
+      output
     end
 
     def nodelist
@@ -25,10 +37,14 @@ module Liquid
       @body.empty?
     end
 
-    def format
-      "{% #{block_name} %}#{@body}{% #{block_delimiter} %}"
+    protected
+
+    def ensure_valid_markup(tag_name, markup, parse_context)
+      unless Syntax.match?(markup)
+        raise SyntaxError, parse_context.locale.t("errors.syntax.tag_unexpected_args", tag: tag_name)
+      end
     end
   end
 
-  Template.register_tag('raw'.freeze, Raw)
+  Template.register_tag('raw', Raw)
 end

lib/liquid/tags/render.rb

@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Render < Tag
+    FOR = 'for'
+    SYNTAX = /(#{QuotedString}+)(\s+(with|#{FOR})\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
+
+    disable_tags "include"
+
+    attr_reader :template_name_expr, :attributes
+
+    def initialize(tag_name, markup, options)
+      super
+
+      raise SyntaxError, options[:locale].t("errors.syntax.render") unless markup =~ SYNTAX
+
+      template_name = Regexp.last_match(1)
+      with_or_for = Regexp.last_match(3)
+      variable_name = Regexp.last_match(4)
+
+      @alias_name = Regexp.last_match(6)
+      @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
+      @template_name_expr = parse_expression(template_name)
+      @for = (with_or_for == FOR)
+
+      @attributes = {}
+      markup.scan(TagAttributes) do |key, value|
+        @attributes[key] = parse_expression(value)
+      end
+    end
+
+    def render_to_output_buffer(context, output)
+      render_tag(context, output)
+    end
+
+    def render_tag(context, output)
+      # Though we evaluate this here we will only ever parse it as a string literal.
+      template_name = context.evaluate(@template_name_expr)
+      raise ArgumentError, options[:locale].t("errors.argument.include") unless template_name
+
+      partial = PartialCache.load(
+        template_name,
+        context: context,
+        parse_context: parse_context
+      )
+
+      context_variable_name = @alias_name || template_name.split('/').last
+
+      render_partial_func = ->(var, forloop) {
+        inner_context               = context.new_isolated_subcontext
+        inner_context.template_name = template_name
+        inner_context.partial       = true
+        inner_context['forloop']    = forloop if forloop
+
+        @attributes.each do |key, value|
+          inner_context[key] = context.evaluate(value)
+        end
+        inner_context[context_variable_name] = var unless var.nil?
+        partial.render_to_output_buffer(inner_context, output)
+        forloop&.send(:increment!)
+      }
+
+      variable = @variable_name_expr ? context.evaluate(@variable_name_expr) : nil
+      if @for && variable.respond_to?(:each) && variable.respond_to?(:count)
+        forloop = Liquid::ForloopDrop.new(template_name, variable.count, nil)
+        variable.each { |var| render_partial_func.call(var, forloop) }
+      else
+        render_partial_func.call(variable, nil)
+      end
+
+      output
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.template_name_expr,
+        ] + @node.attributes.values
+      end
+    end
+  end
+
+  Template.register_tag('render', Render)
+end

lib/liquid/tags/table_row.rb

@@ -1,78 +1,66 @@
+# frozen_string_literal: true
+
 module Liquid
   class TableRow < Block
     Syntax = /(\w+)\s+in\s+(#{QuotedFragment}+)/o
 
+    attr_reader :variable_name, :collection_name, :attributes
+
     def initialize(tag_name, markup, options)
       super
       if markup =~ Syntax
-        @variable_name = $1
-        @collection_name = Expression.parse($2)
-        @attributes = {}
+        @variable_name   = Regexp.last_match(1)
+        @collection_name = parse_expression(Regexp.last_match(2))
+        @attributes      = {}
         markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = Expression.parse(value)
+          @attributes[key] = parse_expression(value)
         end
       else
-        raise SyntaxError.new(options[:locale].t("errors.syntax.table_row".freeze))
+        raise SyntaxError, options[:locale].t("errors.syntax.table_row")
       end
     end
 
-    def render(context)
-      collection = context.evaluate(@collection_name) or return ''.freeze
+    def render_to_output_buffer(context, output)
+      (collection = context.evaluate(@collection_name)) || (return '')
 
-      from = @attributes.key?('offset'.freeze) ? context.evaluate(@attributes['offset'.freeze]).to_i : 0
-      to = @attributes.key?('limit'.freeze) ? from + context.evaluate(@attributes['limit'.freeze]).to_i : nil
+      from = @attributes.key?('offset') ? context.evaluate(@attributes['offset']).to_i : 0
+      to   = @attributes.key?('limit')  ? from + context.evaluate(@attributes['limit']).to_i : nil
 
       collection = Utils.slice_collection(collection, from, to)
+      length     = collection.length
 
-      length = collection.length
+      cols = context.evaluate(@attributes['cols']).to_i
 
-      cols = context.evaluate(@attributes['cols'.freeze]).to_i
-
-      row = 1
-      col = 0
-
-      result = "<tr class=\"row1\">\n"
+      output << "<tr class=\"row1\">\n"
       context.stack do
+        tablerowloop = Liquid::TablerowloopDrop.new(length, cols)
+        context['tablerowloop'] = tablerowloop
 
-        collection.each_with_index do |item, index|
+        collection.each do |item|
           context[@variable_name] = item
-          context['tablerowloop'.freeze] = {
-            'length'.freeze    => length,
-            'index'.freeze     => index + 1,
-            'index0'.freeze    => index,
-            'col'.freeze       => col + 1,
-            'col0'.freeze      => col,
-            'rindex'.freeze    => length - index,
-            'rindex0'.freeze   => length - index - 1,
-            'first'.freeze     => (index == 0),
-            'last'.freeze      => (index == length - 1),
-            'col_first'.freeze => (col == 0),
-            'col_last'.freeze  => (col == cols - 1)
-          }
 
+          output << "<td class=\"col#{tablerowloop.col}\">"
+          super
+          output << '</td>'
 
-          col += 1
-
-          result << "<td class=\"col#{col}\">" << super << '</td>'
-
-          if col == cols and (index != length - 1)
-            col  = 0
-            row += 1
-            result << "</tr>\n<tr class=\"row#{row}\">"
+          if tablerowloop.col_last && !tablerowloop.last
+            output << "</tr>\n<tr class=\"row#{tablerowloop.row + 1}\">"
           end
 
+          tablerowloop.send(:increment!)
         end
       end
-      result << "</tr>\n"
-      result
+
+      output << "</tr>\n"
+      output
     end
 
-    def format
-      tag_main = "#{block_name} #{@variable_name} in #{Expression.format(@collection_name)}"
-      args = @attributes.map { |k, v| "#{k}: #{Expression.format(v)}" }.join(", ")
-      "{% #{tag_main} #{args} %}#{@body.format}{% #{block_delimiter} %}"
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        super + @node.attributes.values + [@node.collection_name]
+      end
     end
   end
 
-  Template.register_tag('tablerow'.freeze, TableRow)
+  Template.register_tag('tablerow', TableRow)
 end

lib/liquid/tags/unless.rb

@@ -1,4 +1,6 @@
-require File.dirname(__FILE__) + '/if'
+# frozen_string_literal: true
+
+require_relative 'if'
 
 module Liquid
   # Unless is a conditional just like 'if' but works on the inverse logic.
@@ -6,26 +8,23 @@ module Liquid
   #   {% unless x < 0 %} x is greater than zero {% endunless %}
   #
   class Unless < If
-    def render(context)
-      context.stack do
-
-        # First condition is interpreted backwards ( if not )
-        first_block = @blocks.first
-        unless first_block.evaluate(context)
-          return first_block.attachment.render(context)
-        end
-
-        # After the first condition unless works just like if
-        @blocks[1..-1].each do |block|
-          if block.evaluate(context)
-            return block.attachment.render(context)
-          end
-        end
-
-        ''.freeze
+    def render_to_output_buffer(context, output)
+      # First condition is interpreted backwards ( if not )
+      first_block = @blocks.first
+      unless first_block.evaluate(context)
+        return first_block.attachment.render_to_output_buffer(context, output)
       end
+
+      # After the first condition unless works just like if
+      @blocks[1..-1].each do |block|
+        if block.evaluate(context)
+          return block.attachment.render_to_output_buffer(context, output)
+        end
+      end
+
+      output
     end
   end
 
-  Template.register_tag('unless'.freeze, Unless)
+  Template.register_tag('unless', Unless)
 end

lib/liquid/template.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Templates are central to liquid.
   # Interpretating templates is a two step process. First you compile the
   # source code you got. During compile time some extensive error checking is performed.
@@ -14,23 +15,19 @@ module Liquid
   #   template.render('user_name' => 'bob')
   #
   class Template
-    DEFAULT_OPTIONS = {
-      :locale => I18n.new
-    }
-
     attr_accessor :root
-    attr_reader :resource_limits
-
-    @@file_system = BlankFileSystem.new
+    attr_reader :resource_limits, :warnings
 
     class TagRegistry
+      include Enumerable
+
       def initialize
         @tags  = {}
         @cache = {}
       end
 
       def [](tag_name)
-        return nil unless @tags.has_key?(tag_name)
+        return nil unless @tags.key?(tag_name)
         return @cache[tag_name] if Liquid.cache_classes
 
         lookup_class(@tags[tag_name]).tap { |o| @cache[tag_name] = o }
@@ -46,10 +43,14 @@ module Liquid
         @cache.delete(tag_name)
       end
 
+      def each(&block)
+        @tags.each(&block)
+      end
+
       private
 
       def lookup_class(name)
-        name.split("::").reject(&:empty?).reduce(Object) { |scope, const| scope.const_get(const) }
+        Object.const_get(name)
       end
     end
 
@@ -60,77 +61,57 @@ module Liquid
       # :lax acts like liquid 2.5 and silently ignores malformed tags in most cases.
       # :warn is the default and will give deprecation warnings when invalid syntax is used.
       # :strict will enforce correct syntax.
-      attr_writer :error_mode
+      attr_accessor :error_mode
+      Template.error_mode = :lax
 
-      # Sets how strict the taint checker should be.
-      # :lax is the default, and ignores the taint flag completely
-      # :warn adds a warning, but does not interrupt the rendering
-      # :error raises an error when tainted output is used
-      attr_writer :taint_mode
-
-      def file_system
-        @@file_system
+      attr_accessor :default_exception_renderer
+      Template.default_exception_renderer = lambda do |exception|
+        exception
       end
 
-      def file_system=(obj)
-        @@file_system = obj
-      end
+      attr_accessor :file_system
+      Template.file_system = BlankFileSystem.new
+
+      attr_accessor :tags
+      Template.tags = TagRegistry.new
+      private :tags=
 
       def register_tag(name, klass)
         tags[name.to_s] = klass
       end
 
-      def tags
-        @tags ||= TagRegistry.new
-      end
-
-      def error_mode
-        @error_mode || :lax
-      end
-
-      def taint_mode
-        @taint_mode || :lax
-      end
-
       # Pass a module with filter methods which should be available
       # to all liquid views. Good for registering the standard library
       def register_filter(mod)
-        Strainer.global_filter(mod)
+        StrainerFactory.add_global_filter(mod)
       end
 
-      def default_resource_limits
-        @default_resource_limits ||= {}
-      end
+      attr_accessor :default_resource_limits
+      Template.default_resource_limits = {}
+      private :default_resource_limits=
 
       # creates a new <tt>Template</tt> object from liquid source code
       # To enable profiling, pass in <tt>profile: true</tt> as an option.
       # See Liquid::Profiler for more information
       def parse(source, options = {})
-        template = Template.new
-        template.parse(source, options)
+        new.parse(source, options)
       end
     end
 
     def initialize
-      @resource_limits = ResourceLimits.new(self.class.default_resource_limits)
+      @rethrow_errors  = false
+      @resource_limits = ResourceLimits.new(Template.default_resource_limits)
     end
 
     # Parse source code.
     # Returns self for easy chaining
     def parse(source, options = {})
-      @options = options
-      @profiling = options[:profile]
-      @line_numbers = options[:line_numbers] || @profiling
-      @root = Document.parse(tokenize(source), DEFAULT_OPTIONS.merge(options))
-      @warnings = nil
+      parse_context = configure_options(options)
+      tokenizer     = parse_context.new_tokenizer(source, start_line_number: @line_numbers && 1)
+      @root         = Document.parse(tokenizer, parse_context)
       self
     end
 
-    def warnings
-      return [] unless @root
-      @warnings ||= @root.warnings
-    end
-
     def registers
       @registers ||= {}
     end
@@ -162,19 +143,19 @@ module Liquid
     #    filters and tags and might be useful to integrate liquid more with its host application
     #
     def render(*args)
-      return ''.freeze if @root.nil?
+      return '' if @root.nil?
 
       context = case args.first
       when Liquid::Context
         c = args.shift
 
         if @rethrow_errors
-          c.exception_handler = ->(e) { true }
+          c.exception_renderer = Liquid::RAISE_EXCEPTION_LAMBDA
         end
 
         c
       when Liquid::Drop
-        drop = args.shift
+        drop         = args.shift
         drop.context = Context.new([drop, assigns], instance_assigns, registers, @rethrow_errors, @resource_limits)
       when Hash
         Context.new([args.shift, assigns], instance_assigns, registers, @rethrow_errors, @resource_limits)
@@ -184,37 +165,34 @@ module Liquid
         raise ArgumentError, "Expected Hash or Liquid::Context as parameter"
       end
 
+      output = nil
+
+      context_register = context.registers.is_a?(StaticRegisters) ? context.registers.static : context.registers
+
       case args.last
       when Hash
         options = args.pop
+        output  = options[:output] if options[:output]
 
-        if options[:registers].is_a?(Hash)
-          self.registers.merge!(options[:registers])
+        options[:registers]&.each do |key, register|
+          context_register[key] = register
         end
 
-        if options[:filters]
-          context.add_filters(options[:filters])
-        end
-
-        if options[:exception_handler]
-          context.exception_handler = options[:exception_handler]
-        end
-      when Module
-        context.add_filters(args.pop)
-      when Array
+        apply_options_to_context(context, options)
+      when Module, Array
         context.add_filters(args.pop)
       end
 
       # Retrying a render resets resource usage
       context.resource_limits.reset
 
+      if @profiling && context.profiler.nil?
+        @profiler = context.profiler = Liquid::Profiler.new
+      end
+
       begin
         # render the nodelist.
-        # for performance reasons we get an array back here. join will make a string out of it.
-        result = with_profiling do
-          @root.render(context)
-        end
-        result.respond_to?(:join) ? result.join : result
+        @root.render_to_output_buffer(context, output || +'')
       rescue Liquid::MemoryError => e
         context.handle_error(e)
       ensure
@@ -227,47 +205,31 @@ module Liquid
       render(*args)
     end
 
+    def render_to_output_buffer(context, output)
+      render(context, output: output)
+    end
+
     private
 
-    # Uses the <tt>Liquid::TemplateParser</tt> regexp to tokenize the passed source
-    def tokenize(source)
-      source = source.source if source.respond_to?(:source)
-      return [] if source.to_s.empty?
-
-      tokens = calculate_line_numbers(source.split(TemplateParser))
-
-      # removes the rogue empty element at the beginning of the array
-      tokens.shift if tokens[0] and tokens[0].empty?
-
-      tokens
-    end
-
-    def calculate_line_numbers(raw_tokens)
-      return raw_tokens unless @line_numbers
-
-      current_line = 1
-      raw_tokens.map do |token|
-        Token.new(token, current_line).tap do
-          current_line += token.count("\n")
-        end
-      end
-    end
-
-    def with_profiling
-      if @profiling && !@options[:included]
+    def configure_options(options)
+      if (profiling = options[:profile])
         raise "Profiler not loaded, require 'liquid/profiler' first" unless defined?(Liquid::Profiler)
-
-        @profiler = Profiler.new
-        @profiler.start
-
-        begin
-          yield
-        ensure
-          @profiler.stop
-        end
-      else
-        yield
       end
+
+      @options      = options
+      @profiling    = profiling
+      @line_numbers = options[:line_numbers] || @profiling
+      parse_context = options.is_a?(ParseContext) ? options : ParseContext.new(options)
+      @warnings     = parse_context.warnings
+      parse_context
+    end
+
+    def apply_options_to_context(context, options)
+      context.add_filters(options[:filters]) if options[:filters]
+      context.global_filter      = options[:global_filter] if options[:global_filter]
+      context.exception_renderer = options[:exception_renderer] if options[:exception_renderer]
+      context.strict_variables   = options[:strict_variables] if options[:strict_variables]
+      context.strict_filters     = options[:strict_filters] if options[:strict_filters]
     end
   end
 end

lib/liquid/template_factory.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module Liquid
+  class TemplateFactory
+    def for(_template_name)
+      Liquid::Template.new
+    end
+  end
+end

lib/liquid/token.rb

@@ -1,18 +0,0 @@
-module Liquid
-  class Token < String
-    attr_reader :line_number
-
-    def initialize(content, line_number)
-      super(content)
-      @line_number = line_number
-    end
-
-    def raw
-      "<raw>"
-    end
-
-    def child(string)
-      Token.new(string, @line_number)
-    end
-  end
-end

lib/liquid/tokenizer.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Tokenizer
+    attr_reader :line_number, :for_liquid_tag
+
+    def initialize(source, line_numbers = false, line_number: nil, for_liquid_tag: false)
+      @source         = source
+      @line_number    = line_number || (line_numbers ? 1 : nil)
+      @for_liquid_tag = for_liquid_tag
+      @tokens         = tokenize
+    end
+
+    def shift
+      (token = @tokens.shift) || return
+
+      if @line_number
+        @line_number += @for_liquid_tag ? 1 : token.count("\n")
+      end
+
+      token
+    end
+
+    private
+
+    def tokenize
+      return [] if @source.to_s.empty?
+
+      return @source.split("\n") if @for_liquid_tag
+
+      tokens = @source.split(TemplateParser)
+
+      # removes the rogue empty element at the beginning of the array
+      tokens.shift if tokens[0]&.empty?
+
+      tokens
+    end
+  end
+end

lib/liquid/usage.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Liquid
+  module Usage
+    def self.increment(name)
+    end
+  end
+end

lib/liquid/utils.rb

@@ -1,27 +1,26 @@
+# frozen_string_literal: true
+
 module Liquid
   module Utils
-
     def self.slice_collection(collection, from, to)
-      if (from != 0 || to != nil) && collection.respond_to?(:load_slice)
+      if (from != 0 || !to.nil?) && collection.respond_to?(:load_slice)
         collection.load_slice(from, to)
       else
         slice_collection_using_each(collection, from, to)
       end
     end
 
-    def self.non_blank_string?(collection)
-      collection.is_a?(String) && collection != ''.freeze
-    end
-
     def self.slice_collection_using_each(collection, from, to)
       segments = []
-      index = 0
+      index    = 0
 
       # Maintains Ruby 1.8.7 String#each behaviour on 1.9
-      return [collection] if non_blank_string?(collection)
+      if collection.is_a?(String)
+        return collection.empty? ? [] : [collection]
+      end
+      return [] unless collection.respond_to?(:each)
 
       collection.each do |item|
-
         if to && to <= index
           break
         end
@@ -35,5 +34,52 @@ module Liquid
 
       segments
     end
+
+    def self.to_integer(num)
+      return num if num.is_a?(Integer)
+      num = num.to_s
+      begin
+        Integer(num)
+      rescue ::ArgumentError
+        raise Liquid::ArgumentError, "invalid integer"
+      end
+    end
+
+    def self.to_number(obj)
+      case obj
+      when Float
+        BigDecimal(obj.to_s)
+      when Numeric
+        obj
+      when String
+        /\A-?\d+\.\d+\z/.match?(obj.strip) ? BigDecimal(obj) : obj.to_i
+      else
+        if obj.respond_to?(:to_number)
+          obj.to_number
+        else
+          0
+        end
+      end
+    end
+
+    def self.to_date(obj)
+      return obj if obj.respond_to?(:strftime)
+
+      if obj.is_a?(String)
+        return nil if obj.empty?
+        obj = obj.downcase
+      end
+
+      case obj
+      when 'now', 'today'
+        Time.now
+      when /\A\d+\z/, Integer
+        Time.at(obj.to_i)
+      when String
+        Time.parse(obj)
+      end
+    rescue ::ArgumentError
+      nil
+    end
   end
 end

lib/liquid/variable.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Holds variables. Variables are only loaded "just in time"
   # and are not evaluated as part of the render stage
   #
@@ -11,64 +12,49 @@ module Liquid
   #   {{ user | link }}
   #
   class Variable
-    FilterParser = /(?:\s+|#{QuotedFragment}|#{ArgumentSeparator})+/o
-    attr_accessor :filters, :name, :warnings
-    attr_accessor :line_number
+    FilterMarkupRegex        = /#{FilterSeparator}\s*(.*)/om
+    FilterParser             = /(?:\s+|#{QuotedFragment}|#{ArgumentSeparator})+/o
+    FilterArgsRegex          = /(?:#{FilterArgumentSeparator}|#{ArgumentSeparator})\s*((?:\w+\s*\:\s*)?#{QuotedFragment})/o
+    JustTagAttributes        = /\A#{TagAttributes}\z/o
+    MarkupWithQuotedFragment = /(#{QuotedFragment})(.*)/om
+
+    attr_accessor :filters, :name, :line_number
+    attr_reader :parse_context
+    alias_method :options, :parse_context
+
     include ParserSwitching
 
-    def initialize(markup, options = {})
-      @markup  = markup
-      @name    = nil
-      @options = options || {}
+    def initialize(markup, parse_context)
+      @markup        = markup
+      @name          = nil
+      @parse_context = parse_context
+      @line_number   = parse_context.line_number
 
-      parse_with_selected_parser(markup)
+      strict_parse_with_error_mode_fallback(markup)
     end
 
     def raw
       @markup
     end
 
-    def format
-      out = Expression.format(@name)
-
-      @filters.each do |filter|
-        out << " | "
-        out << filter[0]
-
-        args = filter[1].map { |arg| Expression.format(arg) }
-
-        if filter.size > 2
-          args += filter[2].map { |key, arg| "#{key}: #{Expression.format(arg)}" }
-        end
-
-        unless args.empty?
-          out << ": "
-          out << args.join(', ')
-        end
-      end
-
-      out
-    end
-
     def markup_context(markup)
       "in \"{{#{markup}}}\""
     end
 
     def lax_parse(markup)
       @filters = []
-      if markup =~ /(#{QuotedFragment})(.*)/om
-        name_markup = $1
-        filter_markup = $2
-        @name = Expression.parse(name_markup)
-        if filter_markup =~ /#{FilterSeparator}\s*(.*)/om
-          filters = $1.scan(FilterParser)
-          filters.each do |f|
-            if f =~ /\w+/
-              filtername = Regexp.last_match(0)
-              filterargs = f.scan(/(?:#{FilterArgumentSeparator}|#{ArgumentSeparator})\s*((?:\w+\s*\:\s*)?#{QuotedFragment})/o).flatten
-              @filters << parse_filter_expressions(filtername, filterargs)
-            end
-          end
+      return unless markup =~ MarkupWithQuotedFragment
+
+      name_markup   = Regexp.last_match(1)
+      filter_markup = Regexp.last_match(2)
+      @name         = Expression.parse(name_markup)
+      if filter_markup =~ FilterMarkupRegex
+        filters = Regexp.last_match(1).scan(FilterParser)
+        filters.each do |f|
+          next unless f =~ /\w+/
+          filtername = Regexp.last_match(0)
+          filterargs = f.scan(FilterArgsRegex).flatten
+          @filters << parse_filter_expressions(filtername, filterargs)
         end
       end
     end
@@ -77,6 +63,8 @@ module Liquid
       @filters = []
       p = Parser.new(markup)
 
+      return if p.look(:end_of_string)
+
       @name = Expression.parse(p.expression)
       while p.consume?(:pipe)
         filtername = p.consume(:id)
@@ -90,38 +78,62 @@ module Liquid
       # first argument
       filterargs = [p.argument]
       # followed by comma separated others
-      while p.consume?(:comma)
-        filterargs << p.argument
-      end
+      filterargs << p.argument while p.consume?(:comma)
       filterargs
     end
 
     def render(context)
-      @filters.inject(context.evaluate(@name)) do |output, (filter_name, filter_args, filter_kwargs)|
+      obj = context.evaluate(@name)
+
+      @filters.each do |filter_name, filter_args, filter_kwargs|
         filter_args = evaluate_filter_expressions(context, filter_args, filter_kwargs)
-        output = context.invoke(filter_name, output, *filter_args)
-      end.tap{ |obj| taint_check(obj) }
+        obj = context.invoke(filter_name, obj, *filter_args)
+      end
+
+      context.apply_global_filter(obj)
+    end
+
+    def render_to_output_buffer(context, output)
+      obj = render(context)
+
+      if obj.is_a?(Array)
+        output << obj.join
+      elsif obj.nil?
+      else
+        output << obj.to_s
+      end
+
+      output
+    end
+
+    def disabled?(_context)
+      false
+    end
+
+    def disabled_tags
+      []
     end
 
     private
 
     def parse_filter_expressions(filter_name, unparsed_args)
-      filter_args = []
-      keyword_args = {}
+      filter_args  = []
+      keyword_args = nil
       unparsed_args.each do |a|
-        if matches = a.match(/\A#{TagAttributes}\z/o)
+        if (matches = a.match(JustTagAttributes))
+          keyword_args           ||= {}
           keyword_args[matches[1]] = Expression.parse(matches[2])
         else
           filter_args << Expression.parse(a)
         end
       end
       result = [filter_name, filter_args]
-      result << keyword_args unless keyword_args.empty?
+      result << keyword_args if keyword_args
       result
     end
 
     def evaluate_filter_expressions(context, filter_args, filter_kwargs)
-      parsed_args = filter_args.map{ |expr| context.evaluate(expr) }
+      parsed_args = filter_args.map { |expr| context.evaluate(expr) }
       if filter_kwargs
         parsed_kwargs = {}
         filter_kwargs.each do |key, expr|
@@ -132,17 +144,9 @@ module Liquid
       parsed_args
     end
 
-    def taint_check(obj)
-      if obj.tainted?
-        @markup =~ QuotedFragment
-        name = Regexp.last_match(0)
-        case Template.taint_mode
-        when :warn
-          @warnings ||= []
-          @warnings << "variable '#{name}' is tainted and was not escaped"
-        when :error
-          raise TaintedError, "Error - variable '#{name}' is tainted and was not escaped"
-        end
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [@node.name] + @node.filters.flatten
       end
     end
   end

lib/liquid/variable_lookup.rb

@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 module Liquid
   class VariableLookup
     SQUARE_BRACKETED = /\A\[(.*)\]\z/m
-    COMMAND_METHODS = ['size'.freeze, 'first'.freeze, 'last'.freeze]
+    COMMAND_METHODS  = ['size', 'first', 'last'].freeze
 
     attr_reader :name, :lookups
 
@@ -14,18 +16,17 @@ module Liquid
 
       name = lookups.shift
       if name =~ SQUARE_BRACKETED
-        @name_expression = true
-        name = Expression.parse($1)
+        name = Expression.parse(Regexp.last_match(1))
       end
       @name = name
 
-      @lookups = lookups
+      @lookups       = lookups
       @command_flags = 0
 
       @lookups.each_index do |i|
         lookup = lookups[i]
         if lookup =~ SQUARE_BRACKETED
-          lookups[i] = Expression.parse($1)
+          lookups[i] = Expression.parse(Regexp.last_match(1))
         elsif COMMAND_METHODS.include?(lookup)
           @command_flags |= 1 << i
         end
@@ -33,7 +34,7 @@ module Liquid
     end
 
     def evaluate(context)
-      name = context.evaluate(@name)
+      name   = context.evaluate(@name)
       object = context.find_variable(name)
 
       @lookups.each_index do |i|
@@ -42,11 +43,11 @@ module Liquid
         # If object is a hash- or array-like object we look for the
         # presence of the key and if its available we return it
         if object.respond_to?(:[]) &&
-          ((object.respond_to?(:has_key?) && object.has_key?(key)) ||
-           (object.respond_to?(:fetch) && key.is_a?(Integer)))
+            ((object.respond_to?(:key?) && object.key?(key)) ||
+             (object.respond_to?(:fetch) && key.is_a?(Integer)))
 
           # if its a proc we will replace the entry with the proc
-          res = context.lookup_and_evaluate(object, key)
+          res    = context.lookup_and_evaluate(object, key)
           object = res.to_liquid
 
           # Some special cases. If the part wasn't in square brackets and
@@ -56,9 +57,11 @@ module Liquid
           object = object.send(key).to_liquid
 
           # No key was present with the desired value and it wasn't one of the directly supported
-          # keywords either. The only thing we got left is to return nil
+          # keywords either. The only thing we got left is to return nil or
+          # raise an exception if `strict_variables` option is set to true
         else
-          return nil
+          return nil unless context.strict_variables
+          raise Liquid::UndefinedVariable, "undefined variable #{key}"
         end
 
         # If we are dealing with a drop here we have to
@@ -69,21 +72,7 @@ module Liquid
     end
 
     def ==(other)
-      self.class == other.class && self.state == other.state
-    end
-
-    def format
-      out = @name_expression ? Expression.format(@name) : @name.dup
-
-      @lookups.each do |lookup|
-        if lookup.is_a?(String) && lookup =~ /^#{VariableSegment}+$/
-          out << ".#{lookup}"
-        else
-          out << "[#{Expression.format(lookup)}]"
-        end
-      end
-
-      out
+      self.class == other.class && state == other.state
     end
 
     protected
@@ -91,5 +80,11 @@ module Liquid
     def state
       [@name, @lookups, @command_flags]
     end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        @node.lookups
+      end
+    end
   end
 end

lib/liquid/version.rb

@@ -1,4 +1,6 @@
 # encoding: utf-8
+# frozen_string_literal: true
+
 module Liquid
-  VERSION = "4.0.0.alpha"
+  VERSION = "5.0.0"
 end

liquid.gemspec

@@ -1,6 +1,8 @@
 # encoding: utf-8
+# frozen_string_literal: true
+
 lib = File.expand_path('../lib/', __FILE__)
-$:.unshift lib unless $:.include?(lib)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
 require "liquid/version"
 
@@ -13,17 +15,20 @@ Gem::Specification.new do |s|
   s.email       = ["tobi@leetsoft.com"]
   s.homepage    = "http://www.liquidmarkup.org"
   s.license     = "MIT"
-  #s.description = "A secure, non-evaling end user template engine with aesthetic markup."
+  # s.description = "A secure, non-evaling end user template engine with aesthetic markup."
 
+  s.required_ruby_version     = ">= 2.5.0"
   s.required_rubygems_version = ">= 1.3.7"
 
-  s.test_files  = Dir.glob("{test}/**/*")
-  s.files       = Dir.glob("{lib}/**/*") + %w(MIT-LICENSE README.md)
+  s.metadata['allowed_push_host'] = 'https://rubygems.org'
 
-  s.extra_rdoc_files  = ["History.md", "README.md"]
+  s.test_files  = Dir.glob("{test}/**/*")
+  s.files       = Dir.glob("{lib}/**/*") + %w(LICENSE README.md)
+
+  s.extra_rdoc_files = ["History.md", "README.md"]
 
   s.require_path = "lib"
 
-  s.add_development_dependency 'rake'
-  s.add_development_dependency 'minitest'
+  s.add_development_dependency('rake', '~> 13.0')
+  s.add_development_dependency('minitest')
 end

performance/benchmark.rb

@@ -1,11 +1,13 @@
+# frozen_string_literal: true
+
 require 'benchmark/ips'
-require File.dirname(__FILE__) + '/theme_runner'
+require_relative 'theme_runner'
 
 Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
 profiler = ThemeRunner.new
 
 Benchmark.ips do |x|
-  x.time = 60
+  x.time   = 10
   x.warmup = 5
 
   puts
@@ -13,5 +15,6 @@ Benchmark.ips do |x|
   puts
 
   x.report("parse:") { profiler.compile }
-  x.report("parse & run:") { profiler.run }
+  x.report("render:") { profiler.render }
+  x.report("parse & render:") { profiler.run }
 end

performance/memory_profile.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require 'benchmark/ips'
+require 'memory_profiler'
+require 'terminal-table'
+require_relative 'theme_runner'
+
+class Profiler
+  LOG_LABEL   = "Profiling: ".rjust(14).freeze
+  REPORTS_DIR = File.expand_path('.memprof', __dir__).freeze
+
+  def self.run
+    puts
+    yield new
+  end
+
+  def initialize
+    @allocated = []
+    @retained  = []
+    @headings  = []
+  end
+
+  def profile(phase, &block)
+    print(LOG_LABEL)
+    print("#{phase}.. ".ljust(10))
+    report = MemoryProfiler.report(&block)
+    puts 'Done.'
+    @headings  << phase.capitalize
+    @allocated << "#{report.scale_bytes(report.total_allocated_memsize)} (#{report.total_allocated} objects)"
+    @retained  << "#{report.scale_bytes(report.total_retained_memsize)} (#{report.total_retained} objects)"
+
+    return if ENV['CI']
+
+    require 'fileutils'
+    report_file = File.join(REPORTS_DIR, "#{sanitize(phase)}.txt")
+    FileUtils.mkdir_p(REPORTS_DIR)
+    report.pretty_print(to_file: report_file, scale_bytes: true)
+  end
+
+  def tabulate
+    table = Terminal::Table.new(headings: @headings.unshift('Phase')) do |t|
+      t << @allocated.unshift('Total allocated')
+      t << @retained.unshift('Total retained')
+    end
+
+    puts
+    puts table
+    puts "\nDetailed report(s) saved to #{REPORTS_DIR}/" unless ENV['CI']
+  end
+
+  def sanitize(string)
+    string.downcase.gsub(/[\W]/, '-').squeeze('-')
+  end
+end
+
+Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
+
+runner = ThemeRunner.new
+Profiler.run do |x|
+  x.profile('parse') { runner.compile }
+  x.profile('render') { runner.render }
+  x.tabulate
+end

performance/profile.rb

@@ -1,19 +1,21 @@
-require 'stackprof' rescue fail("install stackprof extension/gem")
-require File.dirname(__FILE__) + '/theme_runner'
+# frozen_string_literal: true
+
+require 'stackprof'
+require_relative 'theme_runner'
 
 Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
 profiler = ThemeRunner.new
 profiler.run
 
 [:cpu, :object].each do |profile_type|
-  puts "Profiling in #{profile_type.to_s} mode..."
+  puts "Profiling in #{profile_type} mode..."
   results = StackProf.run(mode: profile_type) do
     200.times do
       profiler.run
     end
   end
 
-  if profile_type == :cpu && graph_filename = ENV['GRAPH_FILENAME']
+  if profile_type == :cpu && (graph_filename = ENV['GRAPH_FILENAME'])
     File.open(graph_filename, 'w') do |f|
       StackProf::Report.new(results).print_graphviz(nil, f)
     end

performance/shopify/comment_form.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CommentForm < Liquid::Block
   Syntax = /(#{Liquid::VariableSignature}+)/
 
@@ -5,14 +7,14 @@ class CommentForm < Liquid::Block
     super
 
     if markup =~ Syntax
-      @variable_name = $1
-      @attributes = {}
+      @variable_name = Regexp.last_match(1)
+      @attributes    = {}
     else
-      raise SyntaxError.new("Syntax Error in 'comment_form' - Valid syntax: comment_form [article]")
+      raise SyntaxError, "Syntax Error in 'comment_form' - Valid syntax: comment_form [article]"
     end
   end
 
-  def render(context)
+  def render_to_output_buffer(context, output)
     article = context[@variable_name]
 
     context.stack do
@@ -20,14 +22,16 @@ class CommentForm < Liquid::Block
         'posted_successfully?' => context.registers[:posted_successfully],
         'errors' => context['comment.errors'],
         'author' => context['comment.author'],
-        'email'  => context['comment.email'],
-        'body'   => context['comment.body']
+        'email' => context['comment.email'],
+        'body' => context['comment.body'],
       }
-      wrap_in_form(article, render_all(@nodelist, context))
+
+      output << wrap_in_form(article, render_all(@nodelist, context, output))
+      output
     end
   end
 
   def wrap_in_form(article, input)
-    %Q{<form id="article-#{article.id}-comment-form" class="comment-form" method="post" action="">\n#{input}\n</form>}
+    %(<form id="article-#{article.id}-comment-form" class="comment-form" method="post" action="">\n#{input}\n</form>)
   end
 end

performance/shopify/database.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'yaml'
 
 module Database
@@ -5,7 +7,7 @@ module Database
   # to liquid as assigns. All this is based on Shopify
   def self.tables
     @tables ||= begin
-      db = YAML.load_file(File.dirname(__FILE__) + '/vision.database.yml')
+      db = YAML.load_file("#{__dir__}/vision.database.yml")
 
       # From vision source
       db['products'].each do |product|
@@ -16,9 +18,10 @@ module Database
       end
 
       # key the tables by handles, as this is how liquid expects it.
-      db = db.inject({}) do |assigns, (key, values)|
-        assigns[key] = values.inject({}) { |h, v| h[v['handle']] = v; h; }
-        assigns
+      db = db.each_with_object({}) do |(key, values), assigns|
+        assigns[key] = values.each_with_object({}) do |v, h|
+          h[v['handle']] = v
+        end
       end
 
       # Some standard direct accessors so that the specialized templates
@@ -29,9 +32,9 @@ module Database
       db['article']    = db['blog']['articles'].first
 
       db['cart']       = {
-        'total_price' => db['line_items'].values.inject(0) { |sum, item| sum += item['line_price'] * item['quantity'] },
-        'item_count'  => db['line_items'].values.inject(0) { |sum, item| sum += item['quantity'] },
-        'items'       => db['line_items'].values
+        'total_price' => db['line_items'].values.inject(0) { |sum, item| sum + item['line_price'] * item['quantity'] },
+        'item_count' => db['line_items'].values.inject(0) { |sum, item| sum + item['quantity'] },
+        'items' => db['line_items'].values,
       }
 
       db
@@ -39,7 +42,7 @@ module Database
   end
 end
 
-if __FILE__ == $0
-  p Database.tables['collections']['frontpage'].keys
-  #p Database.tables['blog']['articles']
+if __FILE__ == $PROGRAM_NAME
+  p(Database.tables['collections']['frontpage'].keys)
+  # p Database.tables['blog']['articles']
 end

performance/shopify/json_filter.rb

@@ -1,9 +1,9 @@
+# frozen_string_literal: true
+
 require 'json'
 
 module JsonFilter
-
   def json(object)
-    JSON.dump(object.reject {|k,v| k == "collections" })
+    JSON.dump(object.reject { |k, _v| k == "collections" })
   end
-
 end

performance/shopify/liquid.rb

@@ -1,19 +1,21 @@
-$:.unshift File.dirname(__FILE__) + '/../../lib'
-require File.dirname(__FILE__) + '/../../lib/liquid'
+# frozen_string_literal: true
 
-require File.dirname(__FILE__) + '/comment_form'
-require File.dirname(__FILE__) + '/paginate'
-require File.dirname(__FILE__) + '/json_filter'
-require File.dirname(__FILE__) + '/money_filter'
-require File.dirname(__FILE__) + '/shop_filter'
-require File.dirname(__FILE__) + '/tag_filter'
-require File.dirname(__FILE__) + '/weight_filter'
+$LOAD_PATH.unshift(__dir__ + '/../../lib')
+require_relative '../../lib/liquid'
 
-Liquid::Template.register_tag 'paginate', Paginate
-Liquid::Template.register_tag 'form', CommentForm
+require_relative 'comment_form'
+require_relative 'paginate'
+require_relative 'json_filter'
+require_relative 'money_filter'
+require_relative 'shop_filter'
+require_relative 'tag_filter'
+require_relative 'weight_filter'
 
-Liquid::Template.register_filter JsonFilter
-Liquid::Template.register_filter MoneyFilter
-Liquid::Template.register_filter WeightFilter
-Liquid::Template.register_filter ShopFilter
-Liquid::Template.register_filter TagFilter
+Liquid::Template.register_tag('paginate', Paginate)
+Liquid::Template.register_tag('form', CommentForm)
+
+Liquid::Template.register_filter(JsonFilter)
+Liquid::Template.register_filter(MoneyFilter)
+Liquid::Template.register_filter(WeightFilter)
+Liquid::Template.register_filter(ShopFilter)
+Liquid::Template.register_filter(TagFilter)

performance/shopify/money_filter.rb

@@ -1,13 +1,14 @@
-module MoneyFilter
+# frozen_string_literal: true
 
+module MoneyFilter
   def money_with_currency(money)
     return '' if money.nil?
-    sprintf("$ %.2f USD", money/100.0)
+    format("$ %.2f USD", money / 100.0)
   end
 
   def money(money)
     return '' if money.nil?
-    sprintf("$ %.2f", money/100.0)
+    format("$ %.2f", money / 100.0)
   end
 
   private

performance/shopify/paginate.rb

@@ -1,13 +1,15 @@
+# frozen_string_literal: true
+
 class Paginate < Liquid::Block
-  Syntax     = /(#{Liquid::QuotedFragment})\s*(by\s*(\d+))?/
+  Syntax = /(#{Liquid::QuotedFragment})\s*(by\s*(\d+))?/
 
   def initialize(tag_name, markup, options)
     super
 
     if markup =~ Syntax
-      @collection_name = $1
-      @page_size = if $2
-        $3.to_i
+      @collection_name = Regexp.last_match(1)
+      @page_size       = if Regexp.last_match(2)
+        Regexp.last_match(3).to_i
       else
         20
       end
@@ -17,48 +19,47 @@ class Paginate < Liquid::Block
         @attributes[key] = value
       end
     else
-      raise SyntaxError.new("Syntax Error in tag 'paginate' - Valid syntax: paginate [collection] by number")
+      raise SyntaxError, "Syntax Error in tag 'paginate' - Valid syntax: paginate [collection] by number"
     end
   end
 
-  def render(context)
+  def render_to_output_buffer(context, output)
     @context = context
 
     context.stack do
-      current_page  = context['current_page'].to_i
+      current_page = context['current_page'].to_i
 
       pagination = {
-        'page_size'      => @page_size,
-        'current_page'   => 5,
-        'current_offset' => @page_size * 5
+        'page_size' => @page_size,
+        'current_page' => 5,
+        'current_offset' => @page_size * 5,
       }
 
       context['paginate'] = pagination
 
-      collection_size  = context[@collection_name].size
+      collection_size = context[@collection_name].size
 
-      raise ArgumentError.new("Cannot paginate array '#{@collection_name}'. Not found.") if collection_size.nil?
+      raise ArgumentError, "Cannot paginate array '#{@collection_name}'. Not found." if collection_size.nil?
 
       page_count = (collection_size.to_f / @page_size.to_f).to_f.ceil + 1
 
       pagination['items']      = collection_size
-      pagination['pages']      = page_count -1
-      pagination['previous']   = link('&laquo; Previous', current_page-1 )  unless 1 >= current_page
-      pagination['next']       = link('Next &raquo;', current_page+1 )      unless page_count <= current_page+1
+      pagination['pages']      = page_count - 1
+      pagination['previous']   = link('&laquo; Previous', current_page - 1)  unless 1 >= current_page
+      pagination['next']       = link('Next &raquo;', current_page + 1)      unless page_count <= current_page + 1
       pagination['parts']      = []
 
       hellip_break = false
 
       if page_count > 2
-        1.upto(page_count-1) do |page|
-
+        1.upto(page_count - 1) do |page|
           if current_page == page
             pagination['parts'] << no_link(page)
           elsif page == 1
             pagination['parts'] << link(page, page)
-          elsif page == page_count -1
+          elsif page == page_count - 1
             pagination['parts'] << link(page, page)
-          elsif page <= current_page - @attributes['window_size'] or page >= current_page + @attributes['window_size']
+          elsif page <= current_page - @attributes['window_size'] || page >= current_page + @attributes['window_size']
             next if hellip_break
             pagination['parts'] << no_link('&hellip;')
             hellip_break = true
@@ -78,11 +79,11 @@ class Paginate < Liquid::Block
   private
 
   def no_link(title)
-    { 'title' => title, 'is_link' => false}
+    { 'title' => title, 'is_link' => false }
   end
 
   def link(title, page)
-    { 'title' => title, 'url' => current_url + "?page=#{page}", 'is_link' => true}
+    { 'title' => title, 'url' => current_url + "?page=#{page}", 'is_link' => true }
   end
 
   def current_url

performance/shopify/shop_filter.rb

@@ -1,5 +1,6 @@
-module ShopFilter
+# frozen_string_literal: true
 
+module ShopFilter
   def asset_url(input)
     "/files/1/[shop_id]/[shop_id]/assets/#{input}"
   end
@@ -16,21 +17,21 @@ module ShopFilter
     %(<script src="#{url}" type="text/javascript"></script>)
   end
 
-  def stylesheet_tag(url, media="all")
+  def stylesheet_tag(url, media = "all")
     %(<link href="#{url}" rel="stylesheet" type="text/css"  media="#{media}"  />)
   end
 
-  def link_to(link, url, title="")
-    %|<a href="#{url}" title="#{title}">#{link}</a>|
+  def link_to(link, url, title = "")
+    %(<a href="#{url}" title="#{title}">#{link}</a>)
   end
 
-  def img_tag(url, alt="")
-    %|<img src="#{url}" alt="#{alt}" />|
+  def img_tag(url, alt = "")
+    %(<img src="#{url}" alt="#{alt}" />)
   end
 
   def link_to_vendor(vendor)
     if vendor
-      link_to vendor, url_for_vendor(vendor), vendor
+      link_to(vendor, url_for_vendor(vendor), vendor)
     else
       'Unknown Vendor'
     end
@@ -38,7 +39,7 @@ module ShopFilter
 
   def link_to_type(type)
     if type
-      link_to type, url_for_type(type), type
+      link_to(type, url_for_type(type), type)
     else
       'Unknown Vendor'
     end
@@ -53,36 +54,32 @@ module ShopFilter
   end
 
   def product_img_url(url, style = 'small')
-
-    unless url =~ /\Aproducts\/([\w\-\_]+)\.(\w{2,4})/
+    unless url =~ %r{\Aproducts/([\w\-\_]+)\.(\w{2,4})}
       raise ArgumentError, 'filter "size" can only be called on product images'
     end
 
     case style
     when 'original'
-      return '/files/shops/random_number/' + url
+      '/files/shops/random_number/' + url
     when 'grande', 'large', 'medium', 'compact', 'small', 'thumb', 'icon'
-      "/files/shops/random_number/products/#{$1}_#{style}.#{$2}"
+      "/files/shops/random_number/products/#{Regexp.last_match(1)}_#{style}.#{Regexp.last_match(2)}"
     else
       raise ArgumentError, 'valid parameters for filter "size" are: original, grande, large, medium, compact, small, thumb and icon '
     end
   end
 
   def default_pagination(paginate)
-
     html = []
     html << %(<span class="prev">#{link_to(paginate['previous']['title'], paginate['previous']['url'])}</span>) if paginate['previous']
 
-    for part in paginate['parts']
-
-      if part['is_link']
-        html << %(<span class="page">#{link_to(part['title'], part['url'])}</span>)
+    paginate['parts'].each do |part|
+      html << if part['is_link']
+        %(<span class="page">#{link_to(part['title'], part['url'])}</span>)
       elsif part['title'].to_i == paginate['current_page'].to_i
-        html << %(<span class="page current">#{part['title']}</span>)
+        %(<span class="page current">#{part['title']}</span>)
       else
-        html << %(<span class="deco">#{part['title']}</span>)
+        %(<span class="deco">#{part['title']}</span>)
       end
-
     end
 
     html << %(<span class="next">#{link_to(paginate['next']['title'], paginate['next']['url'])}</span>) if paginate['next']
@@ -106,5 +103,4 @@ module ShopFilter
     result.gsub!(/\A-+/, '') if result[0] == '-'
     result
   end
-
 end

performance/shopify/tag_filter.rb

@@ -1,10 +1,11 @@
-module TagFilter
+# frozen_string_literal: true
 
+module TagFilter
   def link_to_tag(label, tag)
     "<a title=\"Show tag #{tag}\" href=\"/collections/#{@context['handle']}/#{tag}\">#{label}</a>"
   end
 
-  def highlight_active_tag(tag, css_class='active')
+  def highlight_active_tag(tag, css_class = 'active')
     if @context['current_tags'].include?(tag)
       "<span class=\"#{css_class}\">#{tag}</span>"
     else
@@ -14,12 +15,11 @@ module TagFilter
 
   def link_to_add_tag(label, tag)
     tags = (@context['current_tags'] + [tag]).uniq
-    "<a title=\"Show tag #{tag}\" href=\"/collections/#{@context['handle']}/#{tags.join("+")}\">#{label}</a>"
+    "<a title=\"Show tag #{tag}\" href=\"/collections/#{@context['handle']}/#{tags.join('+')}\">#{label}</a>"
   end
 
   def link_to_remove_tag(label, tag)
     tags = (@context['current_tags'] - [tag]).uniq
-    "<a title=\"Show tag #{tag}\" href=\"/collections/#{@context['handle']}/#{tags.join("+")}\">#{label}</a>"
+    "<a title=\"Show tag #{tag}\" href=\"/collections/#{@context['handle']}/#{tags.join('+')}\">#{label}</a>"
   end
-
 end

performance/shopify/weight_filter.rb

@@ -1,11 +1,11 @@
-module WeightFilter
+# frozen_string_literal: true
 
+module WeightFilter
   def weight(grams)
-    sprintf("%.2f", grams / 1000)
+    format("%.2f", grams / 1000)
   end
 
   def weight_with_unit(grams)
     "#{weight(grams)} kg"
   end
-
 end

performance/theme_runner.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This profiler run simulates Shopify.
 # We are looking in the tests directory for liquid files and render them within the designated layout file.
 # We will also export a substantial database to liquid which the templates can render values of.
@@ -6,12 +8,11 @@
 # Shopify which is likely the biggest user of liquid in the world which something to the tune of several
 # million Template#render calls a day.
 
-require File.dirname(__FILE__) + '/shopify/liquid'
-require File.dirname(__FILE__) + '/shopify/database.rb'
+require_relative 'shopify/liquid'
+require_relative 'shopify/database'
 
 class ThemeRunner
   class FileSystem
-
     def initialize(path)
       @path = path
     end
@@ -22,57 +23,104 @@ class ThemeRunner
     end
   end
 
-  # Load all templates into memory, do this now so that
-  # we don't profile IO.
+  # Initialize a new liquid ThemeRunner instance
+  # Will load all templates into memory, do this now so that we don't profile IO.
   def initialize
-    @tests = Dir[File.dirname(__FILE__) + '/tests/**/*.liquid'].collect do |test|
+    @tests = Dir[__dir__ + '/tests/**/*.liquid'].collect do |test|
       next if File.basename(test) == 'theme.liquid'
 
       theme_path = File.dirname(test) + '/theme.liquid'
-
-      [File.read(test), (File.file?(theme_path) ? File.read(theme_path) : nil), test]
+      {
+        liquid: File.read(test),
+        layout: (File.file?(theme_path) ? File.read(theme_path) : nil),
+        template_name: test,
+      }
     end.compact
+
+    compile_all_tests
   end
 
+  # `compile` will test just the compilation portion of liquid without any templates
   def compile
-    # Dup assigns because will make some changes to them
-
-    @tests.each do |liquid, layout, template_name|
-
-      tmpl = Liquid::Template.new
-      tmpl.parse(liquid)
-      tmpl = Liquid::Template.new
-      tmpl.parse(layout)
+    @tests.each do |test_hash|
+      Liquid::Template.new.parse(test_hash[:liquid])
+      Liquid::Template.new.parse(test_hash[:layout])
     end
   end
 
-   def run
+  # `run` is called to benchmark rendering and compiling at the same time
+  def run
+    each_test do |liquid, layout, assigns, page_template, template_name|
+      compile_and_render(liquid, layout, assigns, page_template, template_name)
+    end
+  end
+
+  # `render` is called to benchmark just the render portion of liquid
+  def render
+    @compiled_tests.each do |test|
+      tmpl    = test[:tmpl]
+      assigns = test[:assigns]
+      layout  = test[:layout]
+
+      if layout
+        assigns['content_for_layout'] = tmpl.render!(assigns)
+        layout.render!(assigns)
+      else
+        tmpl.render!(assigns)
+      end
+    end
+  end
+
+  private
+
+  def render_layout(template, layout, assigns)
+    assigns['content_for_layout'] = template.render!(assigns)
+    layout&.render!(assigns)
+  end
+
+  def compile_and_render(template, layout, assigns, page_template, template_file)
+    compiled_test = compile_test(template, layout, assigns, page_template, template_file)
+    render_layout(compiled_test[:tmpl], compiled_test[:layout], compiled_test[:assigns])
+  end
+
+  def compile_all_tests
+    @compiled_tests = []
+    each_test do |liquid, layout, assigns, page_template, template_name|
+      @compiled_tests << compile_test(liquid, layout, assigns, page_template, template_name)
+    end
+    @compiled_tests
+  end
+
+  def compile_test(template, layout, assigns, page_template, template_file)
+    tmpl            = init_template(page_template, template_file)
+    parsed_template = tmpl.parse(template).dup
+
+    if layout
+      parsed_layout = tmpl.parse(layout)
+      { tmpl: parsed_template, assigns: assigns, layout: parsed_layout }
+    else
+      { tmpl: parsed_template, assigns: assigns }
+    end
+  end
+
+  # utility method with similar functionality needed in `compile_all_tests` and `run`
+  def each_test
     # Dup assigns because will make some changes to them
     assigns = Database.tables.dup
 
-    @tests.each do |liquid, layout, template_name|
-
-      # Compute page_tempalte outside of profiler run, uninteresting to profiler
-      page_template = File.basename(template_name, File.extname(template_name))
-      compile_and_render(liquid, layout, assigns, page_template, template_name)
-
+    @tests.each do |test_hash|
+      # Compute page_template outside of profiler run, uninteresting to profiler
+      page_template = File.basename(test_hash[:template_name], File.extname(test_hash[:template_name]))
+      yield(test_hash[:liquid], test_hash[:layout], assigns, page_template, test_hash[:template_name])
     end
   end
 
-
-  def compile_and_render(template, layout, assigns, page_template, template_file)
-    tmpl = Liquid::Template.new
-    tmpl.assigns['page_title'] = 'Page title'
-    tmpl.assigns['template'] = page_template
+  # set up a new Liquid::Template object for use in `compile_and_render` and `compile_test`
+  def init_template(page_template, template_file)
+    tmpl                         = Liquid::Template.new
+    tmpl.assigns['page_title']   = 'Page title'
+    tmpl.assigns['template']     = page_template
     tmpl.registers[:file_system] = ThemeRunner::FileSystem.new(File.dirname(template_file))
-
-    content_for_layout = tmpl.parse(template).render!(assigns)
-
-    if layout
-      assigns['content_for_layout'] = content_for_layout
-      tmpl.parse(layout).render!(assigns)
-    else
-      content_for_layout
-    end
+    tmpl
   end
 end

test/integration/assign_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class AssignTest < Minitest::Test
@@ -8,31 +10,31 @@ class AssignTest < Minitest::Test
     {% assign this-thing = 'Print this-thing' %}
     {{ this-thing }}
     END_TEMPLATE
-    template = Template.parse(template_source)
-    rendered = template.render!
-    assert_equal "Print this-thing", rendered.strip
+    template        = Template.parse(template_source)
+    rendered        = template.render!
+    assert_equal("Print this-thing", rendered.strip)
   end
 
   def test_assigned_variable
     assert_template_result('.foo.',
-                           '{% assign foo = values %}.{{ foo[0] }}.',
-                           'values' => %w{foo bar baz})
+      '{% assign foo = values %}.{{ foo[0] }}.',
+      'values' => %w(foo bar baz))
 
     assert_template_result('.bar.',
-                           '{% assign foo = values %}.{{ foo[1] }}.',
-                           'values' => %w{foo bar baz})
+      '{% assign foo = values %}.{{ foo[1] }}.',
+      'values' => %w(foo bar baz))
   end
 
   def test_assign_with_filter
     assert_template_result('.bar.',
-                           '{% assign foo = values | split: "," %}.{{ foo[1] }}.',
-                           'values' => "foo,bar,baz")
+      '{% assign foo = values | split: "," %}.{{ foo[1] }}.',
+      'values' => "foo,bar,baz")
   end
 
   def test_assign_syntax_error
     assert_match_syntax_error(/assign/,
-                       '{% assign foo not values %}.',
-                       'values' => "foo,bar,baz")
+      '{% assign foo not values %}.',
+      'values' => "foo,bar,baz")
   end
 
   def test_assign_uses_error_mode
@@ -42,7 +44,74 @@ class AssignTest < Minitest::Test
       end
     end
     with_error_mode(:lax) do
-      assert Template.parse("{% assign foo = ('X' | downcase) %}")
+      assert(Template.parse("{% assign foo = ('X' | downcase) %}"))
     end
   end
-end # AssignTest
+
+  def test_expression_with_whitespace_in_square_brackets
+    source = "{% assign r = a[ 'b' ] %}{{ r }}"
+    assert_template_result('result', source, 'a' => { 'b' => 'result' })
+  end
+
+  def test_assign_score_exceeding_resource_limit
+    t = Template.parse("{% assign foo = 42 %}{% assign bar = 23 %}")
+    t.resource_limits.assign_score_limit = 1
+    assert_equal("Liquid error: Memory limits exceeded", t.render)
+    assert(t.resource_limits.reached?)
+
+    t.resource_limits.assign_score_limit = 2
+    assert_equal("", t.render!)
+    refute_nil(t.resource_limits.assign_score)
+  end
+
+  def test_assign_score_exceeding_limit_from_composite_object
+    t = Template.parse("{% assign foo = 'aaaa' | reverse %}")
+
+    t.resource_limits.assign_score_limit = 3
+    assert_equal("Liquid error: Memory limits exceeded", t.render)
+    assert(t.resource_limits.reached?)
+
+    t.resource_limits.assign_score_limit = 5
+    assert_equal("", t.render!)
+  end
+
+  def test_assign_score_of_int
+    assert_equal(1, assign_score_of(123))
+  end
+
+  def test_assign_score_of_string_counts_bytes
+    assert_equal(3, assign_score_of('123'))
+    assert_equal(5, assign_score_of('12345'))
+    assert_equal(9, assign_score_of('すごい'))
+  end
+
+  def test_assign_score_of_array
+    assert_equal(1, assign_score_of([]))
+    assert_equal(2, assign_score_of([123]))
+    assert_equal(6, assign_score_of([123, 'abcd']))
+  end
+
+  def test_assign_score_of_hash
+    assert_equal(1, assign_score_of({}))
+    assert_equal(5, assign_score_of('int' => 123))
+    assert_equal(12, assign_score_of('int' => 123, 'str' => 'abcd'))
+  end
+
+  private
+
+  class ObjectWrapperDrop < Liquid::Drop
+    def initialize(obj)
+      @obj = obj
+    end
+
+    def value
+      @obj
+    end
+  end
+
+  def assign_score_of(obj)
+    context = Liquid::Context.new('drop' => ObjectWrapperDrop.new(obj))
+    Liquid::Template.parse('{% assign obj = drop.value %}').render!(context)
+    context.resource_limits.assign_score
+  end
+end

test/integration/blank_test.rb

@@ -1,11 +1,12 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class FoobarTag < Liquid::Tag
-  def render(*args)
-    " "
+  def render_to_output_buffer(_context, output)
+    output << ' '
+    output
   end
-
-  Liquid::Template.register_tag('foobar', FoobarTag)
 end
 
 class BlankTestFileSystem
@@ -31,7 +32,9 @@ class BlankTest < Minitest::Test
   end
 
   def test_new_tags_are_not_blank_by_default
-    assert_template_result(" "*N, wrap_in_for("{% foobar %}"))
+    with_custom_tag('foobar', FoobarTag) do
+      assert_template_result(" " * N, wrap_in_for("{% foobar %}"))
+    end
   end
 
   def test_loops_are_blank
@@ -47,7 +50,7 @@ class BlankTest < Minitest::Test
   end
 
   def test_mark_as_blank_only_during_parsing
-    assert_template_result(" "*(N+1), wrap(" {% if false %} this never happens, but still, this block is not blank {% endif %}"))
+    assert_template_result(" " * (N + 1), wrap(" {% if false %} this never happens, but still, this block is not blank {% endif %}"))
   end
 
   def test_comments_are_blank
@@ -60,9 +63,9 @@ class BlankTest < Minitest::Test
 
   def test_nested_blocks_are_blank_but_only_if_all_children_are
     assert_template_result("", wrap(wrap(" ")))
-    assert_template_result("\n       but this is not "*(N+1),
-      wrap(%q{{% if true %} {% comment %} this is blank {% endcomment %} {% endif %}
-      {% if true %} but this is not {% endif %}}))
+    assert_template_result("\n       but this is not " * (N + 1),
+      wrap('{% if true %} {% comment %} this is blank {% endcomment %} {% endif %}
+      {% if true %} but this is not {% endif %}'))
   end
 
   def test_assigns_are_blank
@@ -76,31 +79,31 @@ class BlankTest < Minitest::Test
 
   def test_whitespace_is_not_blank_if_other_stuff_is_present
     body = "     x "
-    assert_template_result(body*(N+1), wrap(body))
+    assert_template_result(body * (N + 1), wrap(body))
   end
 
   def test_increment_is_not_blank
-    assert_template_result(" 0"*2*(N+1), wrap("{% assign foo = 0 %} {% increment foo %} {% decrement foo %}"))
+    assert_template_result(" 0" * 2 * (N + 1), wrap("{% assign foo = 0 %} {% increment foo %} {% decrement foo %}"))
   end
 
   def test_cycle_is_not_blank
-    assert_template_result("  "*((N+1)/2)+" ", wrap("{% cycle ' ', ' ' %}"))
+    assert_template_result("  " * ((N + 1) / 2) + " ", wrap("{% cycle ' ', ' ' %}"))
   end
 
   def test_raw_is_not_blank
-    assert_template_result("  "*(N+1), wrap(" {% raw %} {% endraw %}"))
+    assert_template_result("  " * (N + 1), wrap(" {% raw %} {% endraw %}"))
   end
 
   def test_include_is_blank
     Liquid::Template.file_system = BlankTestFileSystem.new
-    assert_template_result "foobar"*(N+1), wrap("{% include 'foobar' %}")
-    assert_template_result " foobar "*(N+1), wrap("{% include ' foobar ' %}")
-    assert_template_result "   "*(N+1), wrap(" {% include ' ' %} ")
+    assert_template_result("foobar" * (N + 1), wrap("{% include 'foobar' %}"))
+    assert_template_result(" foobar " * (N + 1), wrap("{% include ' foobar ' %}"))
+    assert_template_result("   " * (N + 1), wrap(" {% include ' ' %} "))
   end
 
   def test_case_is_blank
     assert_template_result("", wrap(" {% assign foo = 'bar' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} {% endcase %} "))
     assert_template_result("", wrap(" {% assign foo = 'else' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} {% endcase %} "))
-    assert_template_result("   x  "*(N+1), wrap(" {% assign foo = 'else' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} x {% endcase %} "))
+    assert_template_result("   x  " * (N + 1), wrap(" {% assign foo = 'else' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} x {% endcase %} "))
   end
 end

test/integration/block_test.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class BlockTest < Minitest::Test
+  include Liquid
+
+  def test_unexpected_end_tag
+    exc = assert_raises(SyntaxError) do
+      Template.parse("{% if true %}{% endunless %}")
+    end
+    assert_equal(exc.message, "Liquid syntax error: 'endunless' is not a valid delimiter for if tags. use endif")
+  end
+
+  def test_with_custom_tag
+    with_custom_tag('testtag', Block) do
+      assert(Liquid::Template.parse("{% testtag %} {% endtesttag %}"))
+    end
+  end
+
+  def test_custom_block_tags_have_a_default_render_to_output_buffer_method_for_backwards_compatibility
+    klass1 = Class.new(Block) do
+      def render(*)
+        'hello'
+      end
+    end
+
+    with_custom_tag('blabla', klass1) do
+      template = Liquid::Template.parse("{% blabla %} bla {% endblabla %}")
+
+      assert_equal('hello', template.render)
+
+      buf    = +''
+      output = template.render({}, output: buf)
+      assert_equal('hello', output)
+      assert_equal('hello', buf)
+      assert_equal(buf.object_id, output.object_id)
+    end
+
+    klass2 = Class.new(klass1) do
+      def render(*)
+        'foo' + super + 'bar'
+      end
+    end
+
+    with_custom_tag('blabla', klass2) do
+      template = Liquid::Template.parse("{% blabla %} foo {% endblabla %}")
+
+      assert_equal('foohellobar', template.render)
+
+      buf    = +''
+      output = template.render({}, output: buf)
+      assert_equal('foohellobar', output)
+      assert_equal('foohellobar', buf)
+      assert_equal(buf.object_id, output.object_id)
+    end
+  end
+end

test/integration/capture_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class CaptureTest < Minitest::Test
@@ -12,9 +14,9 @@ class CaptureTest < Minitest::Test
     {% capture this-thing %}Print this-thing{% endcapture %}
     {{ this-thing }}
     END_TEMPLATE
-    template = Template.parse(template_source)
-    rendered = template.render!
-    assert_equal "Print this-thing", rendered.strip
+    template        = Template.parse(template_source)
+    rendered        = template.render!
+    assert_equal("Print this-thing", rendered.strip)
   end
 
   def test_capture_to_variable_from_outer_scope_if_existing
@@ -28,9 +30,9 @@ class CaptureTest < Minitest::Test
     {% endif %}
     {{var}}
     END_TEMPLATE
-    template = Template.parse(template_source)
-    rendered = template.render!
-    assert_equal "test-string", rendered.gsub(/\s/, '')
+    template        = Template.parse(template_source)
+    rendered        = template.render!
+    assert_equal("test-string", rendered.gsub(/\s/, ''))
   end
 
   def test_assigning_from_capture
@@ -43,8 +45,14 @@ class CaptureTest < Minitest::Test
     {% endfor %}
     {{ first }}-{{ second }}
     END_TEMPLATE
-    template = Template.parse(template_source)
-    rendered = template.render!
-    assert_equal "3-3", rendered.gsub(/\s/, '')
+    template        = Template.parse(template_source)
+    rendered        = template.render!
+    assert_equal("3-3", rendered.gsub(/\s/, ''))
   end
-end # CaptureTest
+
+  def test_increment_assign_score_by_bytes_not_characters
+    t = Template.parse("{% capture foo %}すごい{% endcapture %}")
+    t.render!
+    assert_equal(9, t.resource_limits.assign_score)
+  end
+end

test/integration/context_test.rb

@@ -1,8 +1,597 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
+class HundredCentes
+  def to_liquid
+    100
+  end
+end
+
+class CentsDrop < Liquid::Drop
+  def amount
+    HundredCentes.new
+  end
+
+  def non_zero?
+    true
+  end
+end
+
+class ContextSensitiveDrop < Liquid::Drop
+  def test
+    @context['test']
+  end
+end
+
+class Category < Liquid::Drop
+  attr_accessor :name
+
+  def initialize(name)
+    @name = name
+  end
+
+  def to_liquid
+    CategoryDrop.new(self)
+  end
+end
+
+class CategoryDrop
+  attr_accessor :category, :context
+  def initialize(category)
+    @category = category
+  end
+end
+
+class CounterDrop < Liquid::Drop
+  def count
+    @count ||= 0
+    @count  += 1
+  end
+end
+
+class ArrayLike
+  def fetch(index)
+  end
+
+  def [](index)
+    @counts        ||= []
+    @counts[index] ||= 0
+    @counts[index]  += 1
+  end
+
+  def to_liquid
+    self
+  end
+end
+
 class ContextTest < Minitest::Test
   include Liquid
 
+  def setup
+    @context = Liquid::Context.new
+  end
+
+  def test_variables
+    @context['string'] = 'string'
+    assert_equal('string', @context['string'])
+
+    @context['num'] = 5
+    assert_equal(5, @context['num'])
+
+    @context['time'] = Time.parse('2006-06-06 12:00:00')
+    assert_equal(Time.parse('2006-06-06 12:00:00'), @context['time'])
+
+    @context['date'] = Date.today
+    assert_equal(Date.today, @context['date'])
+
+    now = Time.now
+    @context['datetime'] = now
+    assert_equal(now, @context['datetime'])
+
+    @context['bool'] = true
+    assert_equal(true, @context['bool'])
+
+    @context['bool'] = false
+    assert_equal(false, @context['bool'])
+
+    @context['nil'] = nil
+    assert_nil(@context['nil'])
+    assert_nil(@context['nil'])
+  end
+
+  def test_variables_not_existing
+    assert_nil(@context['does_not_exist'])
+  end
+
+  def test_scoping
+    @context.push
+    @context.pop
+
+    assert_raises(Liquid::ContextError) do
+      @context.pop
+    end
+
+    assert_raises(Liquid::ContextError) do
+      @context.push
+      @context.pop
+      @context.pop
+    end
+  end
+
+  def test_length_query
+    @context['numbers'] = [1, 2, 3, 4]
+
+    assert_equal(4, @context['numbers.size'])
+
+    @context['numbers'] = { 1 => 1, 2 => 2, 3 => 3, 4 => 4 }
+
+    assert_equal(4, @context['numbers.size'])
+
+    @context['numbers'] = { 1 => 1, 2 => 2, 3 => 3, 4 => 4, 'size' => 1000 }
+
+    assert_equal(1000, @context['numbers.size'])
+  end
+
+  def test_hyphenated_variable
+    @context['oh-my'] = 'godz'
+    assert_equal('godz', @context['oh-my'])
+  end
+
+  def test_add_filter
+    filter = Module.new do
+      def hi(output)
+        output + ' hi!'
+      end
+    end
+
+    context = Context.new
+    context.add_filters(filter)
+    assert_equal('hi? hi!', context.invoke(:hi, 'hi?'))
+
+    context = Context.new
+    assert_equal('hi?', context.invoke(:hi, 'hi?'))
+
+    context.add_filters(filter)
+    assert_equal('hi? hi!', context.invoke(:hi, 'hi?'))
+  end
+
+  def test_only_intended_filters_make_it_there
+    filter = Module.new do
+      def hi(output)
+        output + ' hi!'
+      end
+    end
+
+    context = Context.new
+    assert_equal("Wookie", context.invoke("hi", "Wookie"))
+
+    context.add_filters(filter)
+    assert_equal("Wookie hi!", context.invoke("hi", "Wookie"))
+  end
+
+  def test_add_item_in_outer_scope
+    @context['test'] = 'test'
+    @context.push
+    assert_equal('test', @context['test'])
+    @context.pop
+    assert_equal('test', @context['test'])
+  end
+
+  def test_add_item_in_inner_scope
+    @context.push
+    @context['test'] = 'test'
+    assert_equal('test', @context['test'])
+    @context.pop
+    assert_nil(@context['test'])
+  end
+
+  def test_hierachical_data
+    @context['hash'] = { "name" => 'tobi' }
+    assert_equal('tobi', @context['hash.name'])
+    assert_equal('tobi', @context['hash["name"]'])
+  end
+
+  def test_keywords
+    assert_equal(true, @context['true'])
+    assert_equal(false, @context['false'])
+  end
+
+  def test_digits
+    assert_equal(100, @context['100'])
+    assert_equal(100.00, @context['100.00'])
+  end
+
+  def test_strings
+    assert_equal("hello!", @context['"hello!"'])
+    assert_equal("hello!", @context["'hello!'"])
+  end
+
+  def test_merge
+    @context.merge("test" => "test")
+    assert_equal('test', @context['test'])
+    @context.merge("test" => "newvalue", "foo" => "bar")
+    assert_equal('newvalue', @context['test'])
+    assert_equal('bar', @context['foo'])
+  end
+
+  def test_array_notation
+    @context['test'] = [1, 2, 3, 4, 5]
+
+    assert_equal(1, @context['test[0]'])
+    assert_equal(2, @context['test[1]'])
+    assert_equal(3, @context['test[2]'])
+    assert_equal(4, @context['test[3]'])
+    assert_equal(5, @context['test[4]'])
+  end
+
+  def test_recoursive_array_notation
+    @context['test'] = { 'test' => [1, 2, 3, 4, 5] }
+
+    assert_equal(1, @context['test.test[0]'])
+
+    @context['test'] = [{ 'test' => 'worked' }]
+
+    assert_equal('worked', @context['test[0].test'])
+  end
+
+  def test_hash_to_array_transition
+    @context['colors'] = {
+      'Blue' => ['003366', '336699', '6699CC', '99CCFF'],
+      'Green' => ['003300', '336633', '669966', '99CC99'],
+      'Yellow' => ['CC9900', 'FFCC00', 'FFFF99', 'FFFFCC'],
+      'Red' => ['660000', '993333', 'CC6666', 'FF9999'],
+    }
+
+    assert_equal('003366', @context['colors.Blue[0]'])
+    assert_equal('FF9999', @context['colors.Red[3]'])
+  end
+
+  def test_try_first
+    @context['test'] = [1, 2, 3, 4, 5]
+
+    assert_equal(1, @context['test.first'])
+    assert_equal(5, @context['test.last'])
+
+    @context['test'] = { 'test' => [1, 2, 3, 4, 5] }
+
+    assert_equal(1, @context['test.test.first'])
+    assert_equal(5, @context['test.test.last'])
+
+    @context['test'] = [1]
+    assert_equal(1, @context['test.first'])
+    assert_equal(1, @context['test.last'])
+  end
+
+  def test_access_hashes_with_hash_notation
+    @context['products'] = { 'count' => 5, 'tags' => ['deepsnow', 'freestyle'] }
+    @context['product']  = { 'variants' => [{ 'title' => 'draft151cm' }, { 'title' => 'element151cm' }] }
+
+    assert_equal(5, @context['products["count"]'])
+    assert_equal('deepsnow', @context['products["tags"][0]'])
+    assert_equal('deepsnow', @context['products["tags"].first'])
+    assert_equal('draft151cm', @context['product["variants"][0]["title"]'])
+    assert_equal('element151cm', @context['product["variants"][1]["title"]'])
+    assert_equal('draft151cm', @context['product["variants"][0]["title"]'])
+    assert_equal('element151cm', @context['product["variants"].last["title"]'])
+  end
+
+  def test_access_variable_with_hash_notation
+    @context['foo'] = 'baz'
+    @context['bar'] = 'foo'
+
+    assert_equal('baz', @context['["foo"]'])
+    assert_equal('baz', @context['[bar]'])
+  end
+
+  def test_access_hashes_with_hash_access_variables
+    @context['var']      = 'tags'
+    @context['nested']   = { 'var' => 'tags' }
+    @context['products'] = { 'count' => 5, 'tags' => ['deepsnow', 'freestyle'] }
+
+    assert_equal('deepsnow', @context['products[var].first'])
+    assert_equal('freestyle', @context['products[nested.var].last'])
+  end
+
+  def test_hash_notation_only_for_hash_access
+    @context['array'] = [1, 2, 3, 4, 5]
+    @context['hash']  = { 'first' => 'Hello' }
+
+    assert_equal(1, @context['array.first'])
+    assert_nil(@context['array["first"]'])
+    assert_equal('Hello', @context['hash["first"]'])
+  end
+
+  def test_first_can_appear_in_middle_of_callchain
+    @context['product'] = { 'variants' => [{ 'title' => 'draft151cm' }, { 'title' => 'element151cm' }] }
+
+    assert_equal('draft151cm', @context['product.variants[0].title'])
+    assert_equal('element151cm', @context['product.variants[1].title'])
+    assert_equal('draft151cm', @context['product.variants.first.title'])
+    assert_equal('element151cm', @context['product.variants.last.title'])
+  end
+
+  def test_cents
+    @context.merge("cents" => HundredCentes.new)
+    assert_equal(100, @context['cents'])
+  end
+
+  def test_nested_cents
+    @context.merge("cents" => { 'amount' => HundredCentes.new })
+    assert_equal(100, @context['cents.amount'])
+
+    @context.merge("cents" => { 'cents' => { 'amount' => HundredCentes.new } })
+    assert_equal(100, @context['cents.cents.amount'])
+  end
+
+  def test_cents_through_drop
+    @context.merge("cents" => CentsDrop.new)
+    assert_equal(100, @context['cents.amount'])
+  end
+
+  def test_nested_cents_through_drop
+    @context.merge("vars" => { "cents" => CentsDrop.new })
+    assert_equal(100, @context['vars.cents.amount'])
+  end
+
+  def test_drop_methods_with_question_marks
+    @context.merge("cents" => CentsDrop.new)
+    assert(@context['cents.non_zero?'])
+  end
+
+  def test_context_from_within_drop
+    @context.merge("test" => '123', "vars" => ContextSensitiveDrop.new)
+    assert_equal('123', @context['vars.test'])
+  end
+
+  def test_nested_context_from_within_drop
+    @context.merge("test" => '123', "vars" => { "local" => ContextSensitiveDrop.new })
+    assert_equal('123', @context['vars.local.test'])
+  end
+
+  def test_ranges
+    @context.merge("test" => '5')
+    assert_equal((1..5), @context['(1..5)'])
+    assert_equal((1..5), @context['(1..test)'])
+    assert_equal((5..5), @context['(test..test)'])
+  end
+
+  def test_cents_through_drop_nestedly
+    @context.merge("cents" => { "cents" => CentsDrop.new })
+    assert_equal(100, @context['cents.cents.amount'])
+
+    @context.merge("cents" => { "cents" => { "cents" => CentsDrop.new } })
+    assert_equal(100, @context['cents.cents.cents.amount'])
+  end
+
+  def test_drop_with_variable_called_only_once
+    @context['counter'] = CounterDrop.new
+
+    assert_equal(1, @context['counter.count'])
+    assert_equal(2, @context['counter.count'])
+    assert_equal(3, @context['counter.count'])
+  end
+
+  def test_drop_with_key_called_only_once
+    @context['counter'] = CounterDrop.new
+
+    assert_equal(1, @context['counter["count"]'])
+    assert_equal(2, @context['counter["count"]'])
+    assert_equal(3, @context['counter["count"]'])
+  end
+
+  def test_proc_as_variable
+    @context['dynamic'] = proc { 'Hello' }
+
+    assert_equal('Hello', @context['dynamic'])
+  end
+
+  def test_lambda_as_variable
+    @context['dynamic'] = proc { 'Hello' }
+
+    assert_equal('Hello', @context['dynamic'])
+  end
+
+  def test_nested_lambda_as_variable
+    @context['dynamic'] = { "lambda" => proc { 'Hello' } }
+
+    assert_equal('Hello', @context['dynamic.lambda'])
+  end
+
+  def test_array_containing_lambda_as_variable
+    @context['dynamic'] = [1, 2, proc { 'Hello' }, 4, 5]
+
+    assert_equal('Hello', @context['dynamic[2]'])
+  end
+
+  def test_lambda_is_called_once
+    @context['callcount'] = proc {
+      @global ||= 0
+      @global  += 1
+      @global.to_s
+    }
+
+    assert_equal('1', @context['callcount'])
+    assert_equal('1', @context['callcount'])
+    assert_equal('1', @context['callcount'])
+
+    @global = nil
+  end
+
+  def test_nested_lambda_is_called_once
+    @context['callcount'] = { "lambda" => proc {
+                                            @global ||= 0
+                                            @global  += 1
+                                            @global.to_s
+                                          } }
+
+    assert_equal('1', @context['callcount.lambda'])
+    assert_equal('1', @context['callcount.lambda'])
+    assert_equal('1', @context['callcount.lambda'])
+
+    @global = nil
+  end
+
+  def test_lambda_in_array_is_called_once
+    @context['callcount'] = [1, 2, proc {
+                                     @global ||= 0
+                                     @global  += 1
+                                     @global.to_s
+                                   }, 4, 5]
+
+    assert_equal('1', @context['callcount[2]'])
+    assert_equal('1', @context['callcount[2]'])
+    assert_equal('1', @context['callcount[2]'])
+
+    @global = nil
+  end
+
+  def test_access_to_context_from_proc
+    @context.registers[:magic] = 345392
+
+    @context['magic'] = proc { @context.registers[:magic] }
+
+    assert_equal(345392, @context['magic'])
+  end
+
+  def test_to_liquid_and_context_at_first_level
+    @context['category'] = Category.new("foobar")
+    assert_kind_of(CategoryDrop, @context['category'])
+    assert_equal(@context, @context['category'].context)
+  end
+
+  def test_interrupt_avoids_object_allocations
+    assert_no_object_allocations do
+      @context.interrupt?
+    end
+  end
+
+  def test_context_initialization_with_a_proc_in_environment
+    contx = Context.new([test: ->(c) { c['poutine'] }], test: :foo)
+
+    assert(contx)
+    assert_nil(contx['poutine'])
+  end
+
+  def test_apply_global_filter
+    global_filter_proc = ->(output) { "#{output} filtered" }
+
+    context = Context.new
+    context.global_filter = global_filter_proc
+
+    assert_equal('hi filtered', context.apply_global_filter('hi'))
+  end
+
+  def test_static_environments_are_read_with_lower_priority_than_environments
+    context = Context.build(
+      static_environments: { 'shadowed' => 'static', 'unshadowed' => 'static' },
+      environments: { 'shadowed' => 'dynamic' }
+    )
+
+    assert_equal('dynamic', context['shadowed'])
+    assert_equal('static', context['unshadowed'])
+  end
+
+  def test_apply_global_filter_when_no_global_filter_exist
+    context = Context.new
+    assert_equal('hi', context.apply_global_filter('hi'))
+  end
+
+  def test_new_isolated_subcontext_does_not_inherit_variables
+    super_context = Context.new
+    super_context['my_variable'] = 'some value'
+    subcontext = super_context.new_isolated_subcontext
+
+    assert_nil(subcontext['my_variable'])
+  end
+
+  def test_new_isolated_subcontext_inherits_static_environment
+    super_context = Context.build(static_environments: { 'my_environment_value' => 'my value' })
+    subcontext    = super_context.new_isolated_subcontext
+
+    assert_equal('my value', subcontext['my_environment_value'])
+  end
+
+  def test_new_isolated_subcontext_inherits_resource_limits
+    resource_limits = ResourceLimits.new({})
+    super_context   = Context.new({}, {}, {}, false, resource_limits)
+    subcontext      = super_context.new_isolated_subcontext
+    assert_equal(resource_limits, subcontext.resource_limits)
+  end
+
+  def test_new_isolated_subcontext_inherits_exception_renderer
+    super_context = Context.new
+    super_context.exception_renderer = ->(_e) { 'my exception message' }
+    subcontext = super_context.new_isolated_subcontext
+    assert_equal('my exception message', subcontext.handle_error(Liquid::Error.new))
+  end
+
+  def test_new_isolated_subcontext_does_not_inherit_non_static_registers
+    registers = {
+      my_register: :my_value,
+    }
+    super_context = Context.new({}, {}, StaticRegisters.new(registers))
+    super_context.registers[:my_register] = :my_alt_value
+    subcontext                            = super_context.new_isolated_subcontext
+    assert_equal(:my_value, subcontext.registers[:my_register])
+  end
+
+  def test_new_isolated_subcontext_inherits_static_registers
+    super_context = Context.build(registers: { my_register: :my_value })
+    subcontext    = super_context.new_isolated_subcontext
+    assert_equal(:my_value, subcontext.registers[:my_register])
+  end
+
+  def test_new_isolated_subcontext_registers_do_not_pollute_context
+    super_context                      = Context.build(registers: { my_register: :my_value })
+    subcontext                         = super_context.new_isolated_subcontext
+    subcontext.registers[:my_register] = :my_alt_value
+    assert_equal(:my_value, super_context.registers[:my_register])
+  end
+
+  def test_new_isolated_subcontext_inherits_filters
+    my_filter = Module.new do
+      def my_filter(*)
+        'my filter result'
+      end
+    end
+
+    super_context = Context.new
+    super_context.add_filters([my_filter])
+    subcontext    = super_context.new_isolated_subcontext
+    template      = Template.parse('{{ 123 | my_filter }}')
+    assert_equal('my filter result', template.render(subcontext))
+  end
+
+  def test_disables_tag_specified
+    context = Context.new
+    context.with_disabled_tags(%w(foo bar)) do
+      assert_equal(true, context.tag_disabled?("foo"))
+      assert_equal(true, context.tag_disabled?("bar"))
+      assert_equal(false, context.tag_disabled?("unknown"))
+    end
+  end
+
+  def test_disables_nested_tags
+    context = Context.new
+    context.with_disabled_tags(["foo"]) do
+      context.with_disabled_tags(["foo"]) do
+        assert_equal(true, context.tag_disabled?("foo"))
+        assert_equal(false, context.tag_disabled?("bar"))
+      end
+      context.with_disabled_tags(["bar"]) do
+        assert_equal(true, context.tag_disabled?("foo"))
+        assert_equal(true, context.tag_disabled?("bar"))
+        context.with_disabled_tags(["foo"]) do
+          assert_equal(true, context.tag_disabled?("foo"))
+          assert_equal(true, context.tag_disabled?("bar"))
+        end
+      end
+      assert_equal(true, context.tag_disabled?("foo"))
+      assert_equal(false, context.tag_disabled?("bar"))
+    end
+  end
+
   def test_override_global_filter
     global = Module.new do
       def notice(output)
@@ -17,16 +606,30 @@ class ContextTest < Minitest::Test
     end
 
     with_global_filter(global) do
-      assert_equal 'Global test', Template.parse("{{'test' | notice }}").render!
-      assert_equal 'Local test', Template.parse("{{'test' | notice }}").render!({}, :filters => [local])
+      assert_equal('Global test', Template.parse("{{'test' | notice }}").render!)
+      assert_equal('Local test', Template.parse("{{'test' | notice }}").render!({}, filters: [local]))
     end
   end
 
   def test_has_key_will_not_add_an_error_for_missing_keys
-    with_error_mode :strict do
+    with_error_mode(:strict) do
       context = Context.new
-      context.has_key?('unknown')
-      assert_empty context.errors
+      context.key?('unknown')
+      assert_empty(context.errors)
     end
   end
-end
+
+  private
+
+  def assert_no_object_allocations
+    unless RUBY_ENGINE == 'ruby'
+      skip("stackprof needed to count object allocations")
+    end
+    require 'stackprof'
+
+    profile = StackProf.run(mode: :object) do
+      yield
+    end
+    assert_equal(0, profile[:samples])
+  end
+end # ContextTest

test/integration/document_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class DocumentTest < Minitest::Test
@@ -7,13 +9,13 @@ class DocumentTest < Minitest::Test
     exc = assert_raises(SyntaxError) do
       Template.parse("{% else %}")
     end
-    assert_equal exc.message, "Liquid syntax error: Unexpected outer 'else' tag"
+    assert_equal(exc.message, "Liquid syntax error: Unexpected outer 'else' tag")
   end
 
   def test_unknown_tag
     exc = assert_raises(SyntaxError) do
       Template.parse("{% foo %}")
     end
-    assert_equal exc.message, "Liquid syntax error: Unknown tag 'foo'"
+    assert_equal(exc.message, "Liquid syntax error: Unknown tag 'foo'")
   end
 end