Reserve future support for comment line before a tag name

handle carriage return in newlines_to_br

.github/probots.yml

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

.github/workflows/liquid.yml

@@ -0,0 +1,39 @@
+name: Liquid
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        entry:
+          - { ruby: 2.5, allowed-failure: false } # minimum supported
+          - { ruby: 3.0, allowed-failure: false } # latest
+          - { 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

@@ -1,2 +1,10 @@
+*~
 *.gem
+*.swp
 pkg
+*.rbc
+.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'

CHANGELOG

@@ -1,46 +0,0 @@
-* Make context and assign work the same
-
-* Ruby 1.9.1 bugfixes
-
-* Fix LiquidView for Rails 2.2. Fix local assigns for all versions of Rails
-
-* Fixed gem install rake task
-* Improve Error encapsulation in liquid by maintaining a own set of exceptions instead of relying on ruby build ins
-
-* Added If with or / and expressions
-
-* Implemented .to_liquid for all objects which can be passed to liquid like Strings Arrays Hashes Numerics and Booleans. To export new objects to liquid just implement .to_liquid on them and return objects which themselves have .to_liquid methods.
-
-* Added more tags to standard library
-
-* Added include tag ( like partials in rails )
-
-* [...] Gazillion of detail improvements
-
-* Added strainers as filter hosts for better security [Tobias Luetke]
-
-* Fixed that rails integration would call filter with the wrong "self" [Michael Geary]
-
-* Fixed bad error reporting when a filter called a method which doesn't exist. Liquid told you that it couldn't find the filter which was obviously misleading [Tobias Luetke]
-
-* Removed count helper from standard lib. use size [Tobias Luetke]
-
-* Fixed bug with string filter parameters failing to tolerate commas in strings. [Paul Hammond]
-
-* Improved filter parameters. Filter parameters are now context sensitive; Types are resolved according to the rules of the context. Multiple parameters are now separated by the Liquid::ArgumentSeparator: , by default [Paul Hammond]
-
-  {{ 'Typo' | link_to: 'http://typo.leetsoft.com', 'Typo - a modern weblog engine' }}
-
-
-* Added Liquid::Drop. A base class which you can use for exporting proxy objects to liquid which can acquire more data when used in liquid. [Tobias Luetke]
-
-  class ProductDrop < Liquid::Drop
-    def top_sales
-       Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
-    end
-  end
-  t = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {% endfor %} '  )
-  t.render('product' => ProductDrop.new )
-
-
-* Added filter parameters support. Example: {{ date | format_date: "%Y" }} [Paul Hammond]

CONTRIBUTING.md

@@ -0,0 +1,25 @@
+# How to contribute
+
+## Things we will merge
+
+* Bugfixes
+* Performance improvements
+* Features that are likely to be useful to the majority of Liquid users
+
+## Things we won't merge
+
+* 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/or run a performance benchmark
+* Make sure all tests pass (`bundle exec rake`)
+* Create a pull request
+

Gemfile

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+git_source(:github) do |repo_name|
+  "https://github.com/#{repo_name}.git"
+end
+
+gemspec
+
+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 'rubocop', '~> 1.4', require: false
+  gem 'rubocop-performance', require: false
+
+  platform :mri, :truffleruby do
+    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'inline-comment'
+  end
+end

History.md

@@ -0,0 +1,326 @@
+# Liquid Change Log
+
+## Unreleased
+
+### Features
+* Allow `#` to be used as an inline comment tag (#1401) [Dylan Thacker-Smith]
+
+## 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 break and continue tags inside included templates in loops (#1072) [Justin Li]
+
+## 4.0.2 / 2019-03-08
+
+### 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
+
+* Remove duplicate `index0` key in TableRow tag (#502) [Alfred Xing]
+
+## 3.0.0 / 2014-11-12
+
+* 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]
+* 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]
+* 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]
+
+## 2.6.3 / 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]
+* Prevent arbitrary method invocation on condition objects (#274) [Dylan Thacker-Smith]
+
+## 2.6.0 / 2013-11-25
+
+IMPORTANT: Liquid 2.6 is going to be the last version of Liquid which maintains explicit Ruby 1.8 compatability.
+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]
+* 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]
+* 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]
+* 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), [jsw0528]
+
+## 2.5.3 / 2013-10-09
+
+* #232, #234, #237: Fix map filter bugs [Florian Weingarten]
+
+## 2.5.2 / 2013-09-03 / deleted
+
+Yanked from rubygems, as it contained too many changes that broke compatibility. Those changes will be on following major releases.
+
+## 2.5.1 / 2013-07-24
+
+* #230: Fix security issue with map filter, Use invoke_drop in map filter [Florian Weingarten]
+
+## 2.5.0 / 2013-03-06
+
+* Prevent Object methods from being called on drops
+* Avoid symbol injection from liquid
+* Added break and continue statements
+* Fix filter parser for args without space separators
+* Add support for filter keyword arguments
+
+
+## 2.4.0 / 2012-08-03
+
+* Performance improvements
+* Allow filters in `assign`
+* Add `modulo` filter
+* Ruby 1.8, 1.9, and Rubinius compatibility fixes
+* Add support for `quoted['references']` in `tablerow`
+* Add support for Enumerable to `tablerow`
+* `strip_html` filter removes html comments
+
+
+## 2.3.0 / 2011-10-16
+
+* Several speed/memory improvements
+* Numerous bug fixes
+* Added support for MRI 1.9, Rubinius, and JRuby
+* Added support for integer drop parameters
+* Added epoch support to `date` filter
+* New `raw` tag that suppresses parsing
+* Added `else` option to `for` tag
+* New `increment` tag
+* New `split` filter
+
+
+## 2.2.1 / 2010-08-23
+
+* Added support for literal tags
+
+
+## 2.2.0 / 2010-08-22
+
+* Compatible with Ruby 1.8.7, 1.9.1 and 1.9.2-p0
+* Merged some changed made by the community
+
+
+## 1.9.0 / 2008-03-04
+
+* Fixed gem install rake task
+* Improve Error encapsulation in liquid by maintaining a own set of exceptions instead of relying on ruby build ins
+
+
+## Before 1.9.0
+
+* Added If with or / and expressions
+* Implemented .to_liquid for all objects which can be passed to liquid like Strings Arrays Hashes Numerics and Booleans. To export new objects to liquid just implement .to_liquid on them and return objects which themselves have .to_liquid methods.
+* Added more tags to standard library
+* Added include tag ( like partials in rails )
+* [...] Gazillion of detail improvements
+* Added strainers as filter hosts for better security [Tobias Luetke]
+* Fixed that rails integration would call filter with the wrong "self" [Michael Geary]
+* Fixed bad error reporting when a filter called a method which doesn't exist. Liquid told you that it couldn't find the filter which was obviously misleading [Tobias Luetke]
+* Removed count helper from standard lib. use size [Tobias Luetke]
+* Fixed bug with string filter parameters failing to tolerate commas in strings. [Paul Hammond]
+* Improved filter parameters. Filter parameters are now context sensitive; Types are resolved according to the rules of the context. Multiple parameters are now separated by the Liquid::ArgumentSeparator: , by default [Paul Hammond]
+    {{ 'Typo' | link_to: 'http://typo.leetsoft.com', 'Typo - a modern weblog engine' }}
+* Added Liquid::Drop. A base class which you can use for exporting proxy objects to liquid which can acquire more data when used in liquid. [Tobias Luetke]
+
+  class ProductDrop < Liquid::Drop
+    def top_sales
+       Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
+    end
+  end
+  t = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {% endfor %} '  )
+  t.render('product' => ProductDrop.new )
+* Added filter parameters support. Example: {{ date | format_date: "%Y" }} [Paul Hammond]

History.txt

@@ -1,44 +0,0 @@
-1.9.0 / 2008-03-04
-
-* Fixed gem install rake task
-* Improve Error encapsulation in liquid by maintaining a own set of exceptions instead of relying on ruby build ins
-
-Before 1.9.0
-
-* Added If with or / and expressions
-
-* Implemented .to_liquid for all objects which can be passed to liquid like Strings Arrays Hashes Numerics and Booleans. To export new objects to liquid just implement .to_liquid on them and return objects which themselves have .to_liquid methods. 
-
-* Added more tags to standard library
-
-* Added include tag ( like partials in rails )
-
-* [...] Gazillion of detail improvements
-
-* Added strainers as filter hosts for better security [Tobias Luetke]
-
-* Fixed that rails integration would call filter with the wrong "self" [Michael Geary]
-
-* Fixed bad error reporting when a filter called a method which doesn't exist. Liquid told you that it couldn't find the filter which was obviously misleading [Tobias Luetke]
-
-* Removed count helper from standard lib. use size [Tobias Luetke]
-
-* Fixed bug with string filter parameters failing to tolerate commas in strings. [Paul Hammond]
-
-* Improved filter parameters. Filter parameters are now context sensitive; Types are resolved according to the rules of the context. Multiple parameters are now separated by the Liquid::ArgumentSeparator: , by default [Paul Hammond]
-	
-	{{ 'Typo' | link_to: 'http://typo.leetsoft.com', 'Typo - a modern weblog engine' }}
-	
-
-* Added Liquid::Drop. A base class which you can use for exporting proxy objects to liquid which can acquire more data when used in liquid. [Tobias Luetke] 
-
-  class ProductDrop < Liquid::Drop
-    def top_sales
-       Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
-    end
-  end   
-  t = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {% endfor %} '  )
-  t.render('product' => ProductDrop.new )
-
-
-* Added filter parameters support. Example: {{ date | format_date: "%Y" }} [Paul Hammond]

Manifest.txt

@@ -1,34 +0,0 @@
-CHANGELOG
-History.txt
-MIT-LICENSE
-Manifest.txt
-README.txt
-Rakefile
-init.rb
-lib/extras/liquid_view.rb
-lib/liquid.rb
-lib/liquid/block.rb
-lib/liquid/condition.rb
-lib/liquid/context.rb
-lib/liquid/document.rb
-lib/liquid/drop.rb
-lib/liquid/errors.rb
-lib/liquid/extensions.rb
-lib/liquid/file_system.rb
-lib/liquid/htmltags.rb
-lib/liquid/module_ex.rb
-lib/liquid/standardfilters.rb
-lib/liquid/strainer.rb
-lib/liquid/tag.rb
-lib/liquid/tags/assign.rb
-lib/liquid/tags/capture.rb
-lib/liquid/tags/case.rb
-lib/liquid/tags/comment.rb
-lib/liquid/tags/cycle.rb
-lib/liquid/tags/for.rb
-lib/liquid/tags/if.rb
-lib/liquid/tags/ifchanged.rb
-lib/liquid/tags/include.rb
-lib/liquid/tags/unless.rb
-lib/liquid/template.rb
-lib/liquid/variable.rb

README.md

@@ -0,0 +1,114 @@
+[![Build Status](https://api.travis-ci.org/Shopify/liquid.svg?branch=master)](http://travis-ci.org/Shopify/liquid)
+[![Inline docs](http://inch-ci.org/github/Shopify/liquid.svg?branch=master)](http://inch-ci.org/github/Shopify/liquid)
+
+# Liquid template engine
+
+* [Contributing guidelines](CONTRIBUTING.md)
+* [Version history](History.md)
+* [Liquid documentation from Shopify](http://docs.shopify.com/themes/liquid-basics)
+* [Liquid Wiki at GitHub](https://github.com/Shopify/liquid/wiki)
+* [Website](http://liquidmarkup.org/)
+
+## Introduction
+
+Liquid is a template engine which was written with very specific requirements:
+
+* It has to have beautiful and simple markup. Template engines which don't produce good looking markup are no fun to use.
+* It needs to be non evaling and secure. Liquid templates are made so that users can edit them. You don't want to run code on your server which your users wrote.
+* It has to be stateless. Compile and render steps have to be separate so that the expensive parsing and compiling can be done once and later on you can just render it passing in a hash with local variables and objects.
+
+## Why you should use Liquid
+
+* You want to allow your users to edit the appearance of your application but don't want them to run **insecure code on your server**.
+* You want to render templates directly from the database.
+* You like smarty (PHP) style template engines.
+* You need a template engine which does HTML just as well as emails.
+* You don't like the markup of your current templating engine.
+
+## What does it look like?
+
+```html
+<ul id="products">
+  {% for product in products %}
+    <li>
+      <h2>{{ product.name }}</h2>
+      Only {{ product.price | price }}
+
+      {{ product.description | prettyprint | paragraph }}
+    </li>
+  {% endfor %}
+</ul>
+```
+
+## 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.
+
+```ruby
+@template = Liquid::Template.parse("hi {{name}}") # Parses and compiles the template
+@template.render('name' => 'tobi')                # => "hi tobi"
+```
+
+### Error Modes
+
+Setting the error mode of Liquid lets you specify how strictly you want your templates to be interpreted.
+Normally the parser is very lax and will accept almost anything without error. Unfortunately this can make
+it very hard to debug and can lead to unexpected behaviour. 
+
+Liquid also comes with a stricter parser that can be used when editing templates to give better error messages
+when templates are invalid. You can enable this new parser like this:
+
+```ruby
+Liquid::Template.error_mode = :strict # Raises a SyntaxError when invalid syntax is used
+Liquid::Template.error_mode = :warn # Adds errors to template.errors but continues as normal
+Liquid::Template.error_mode = :lax # The default mode, accepts almost anything.
+```
+
+If you want to set the error mode only on specific templates you can pass `:error_mode` as an option to `parse`:
+```ruby
+Liquid::Template.parse(source, :error_mode => :strict)
+```
+This is useful for doing things like enabling strict mode only in the theme editor.
+
+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.

README.txt

@@ -1,38 +0,0 @@
-= Liquid template engine
-
-Liquid is a template engine which I wrote for very specific requirements
-
-* It has to have beautiful and simple markup. 
-  Template engines which don't produce good looking markup are no fun to use. 
-* It needs to be non evaling and secure. Liquid templates are made so that users can edit them. You don't want to run code on your server which your users wrote. 
-* It has to be stateless. Compile and render steps have to be seperate so that the expensive parsing and compiling can be done once and later on you can 
-  just render it   passing in a hash with local variables and objects.
-
-== Why should i use Liquid
-
-* You want to allow your users to edit the appearance of your application but don't want them to run insecure code on your server.
-* You want to render templates directly from the database
-* You like smarty style template engines 
-* You need a template engine which does HTML just as well as Emails
-* You don't like the markup of your current one
-
-== What does it look like?
-
-	<ul id="products">  
-	  {% for product in products %}
-	    <li>
-	      <h2>{{product.name}}</h2>
-	      Only {{product.price | price }}
-  
-	      {{product.description | prettyprint | paragraph }}
- 	    </li>      
-	  {% endfor %}  
-	</ul>
-
-== Howto use Liquid
-
-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. 
-
-	@template = Liquid::Template.parse("hi {{name}}") # Parses and compiles the template
-	@template.render( 'name' => 'tobi' )              # => "hi tobi" 

Rakefile

@@ -1,44 +1,112 @@
-#!/usr/bin/env ruby
-require 'rubygems'
+# frozen_string_literal: true
+
 require 'rake'
 require 'rake/testtask'
-require 'rake/gempackagetask'
+$LOAD_PATH.unshift(File.expand_path("../lib", __FILE__))
+require "liquid/version"
 
-task :default => 'test'
+task(default: [:test, :rubocop])
 
-Rake::TestTask.new(:test) do |t|
-  t.libs << "lib"
-  t.libs << "test"
-  t.pattern = 'test/*_test.rb'
-  t.verbose = false
+desc('run test suite with default parser')
+Rake::TestTask.new(:base_test) do |t|
+  t.libs << 'lib' << 'test'
+  t.test_files = FileList['test/{integration,unit}/**/*_test.rb']
+  t.verbose    = false
 end
 
-gemspec = eval(File.read('liquid.gemspec'))
-Rake::GemPackageTask.new(gemspec) do |pkg|
-  pkg.gem_spec = gemspec
+Rake::TestTask.new(:integration_test) do |t|
+  t.libs << 'lib' << 'test'
+  t.test_files = FileList['test/integration/**/*_test.rb']
+  t.verbose    = false
 end
 
-desc "build the gem and release it to rubygems.org"
-task :release => :gem do
-  sh "gem push pkg/liquid-#{gemspec.version}.gem"
+desc('run test suite with warn error mode')
+task :warn_test do
+  ENV['LIQUID_PARSER_MODE'] = 'warn'
+  Rake::Task['base_test'].invoke
+end
+
+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 :build do
+  system "gem build liquid.gemspec"
+end
+
+task install: :build do
+  system "gem install liquid-#{Liquid::VERSION}.gem"
+end
+
+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"
+  system "rm liquid-#{Liquid::VERSION}.gem"
+end
+
+namespace :benchmark do
+  desc "Run the liquid benchmark with lax parsing"
+  task :run do
+    ruby "./performance/benchmark.rb lax"
+  end
+
+  desc "Run the liquid benchmark with strict parsing"
+  task :strict do
+    ruby "./performance/benchmark.rb strict"
+  end
 end
 
 namespace :profile do
-
-  
-  task :default => [:run]
-  
-  desc "Run the liquid profile/perforamce coverage"
+  desc "Run the liquid profile/performance coverage"
   task :run do
-  
-    ruby "performance/shopify.rb"
-  
+    ruby "./performance/profile.rb"
   end
 
-  desc "Run KCacheGrind" 
-  task :grind => :run  do
-    system "kcachegrind /tmp/liquid.rubyprof_calltreeprinter.txt"
+  desc "Run the liquid profile/performance coverage with strict parsing"
+  task :strict do
+    ruby "./performance/profile.rb strict"
   end
 end
 
+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)
@@ -17,21 +19,28 @@ module ProductsFilter
 end
 
 class Servlet < LiquidServlet
-  
   def index
     { 'date' => Time.now }
   end
 
   def products
-    { 'products' => products_list, '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' }]
+  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
@@ -10,19 +11,20 @@ class LiquidServlet < WEBrick::HTTPServlet::AbstractServlet
 
   private
 
-  def handle(type, req, res)
-    @request, @response = req, res
+  def handle(_type, req, res)
+    @request  = req
+    @response = res
 
-    @request.path_info =~ /(\w+)$/
-    @action = $1 || 'index'    
+    @request.path_info =~ /(\w+)\z/
+    @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

@@ -1,12 +1,14 @@
+# frozen_string_literal: true
+
 require 'webrick'
 require 'rexml/document'
 
-require File.dirname(__FILE__) + '/../../lib/liquid'
-require File.dirname(__FILE__) + '/liquid_servlet'
-require File.dirname(__FILE__) + '/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

example/server/templates/index.liquid

@@ -3,4 +3,4 @@
 <p>It is {{date}}</p>
 
 
-<p>Check out the <a href="http://localhost:3000/products">Products</a> screen </p>
+<p>Check out the <a href="/products">Products</a> screen </p>

example/server/templates/products.liquid

@@ -1,23 +1,27 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
-	"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
-	<head>
-		<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
-		<meta http-equiv="Content-Language" content="en-us" />
+  <head>
+    <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
+    <meta http-equiv="Content-Language" content="en-us" />
 
-		<title>products</title>
+    <title>products</title>
 
-		<meta name="ROBOTS" content="ALL" />
-		<meta http-equiv="imagetoolbar" content="no" />
-		<meta name="MSSmartTagsPreventParsing" content="true" />
-		<meta name="Copyright" content="(c) 2005 Copyright content:  Copyright design: Tobias Luetke" />
-		<!-- (c) Copyright 2005 by Tobias Luetke All Rights Reserved. -->
-	</head>
+    <meta name="ROBOTS" content="ALL" />
+    <meta http-equiv="imagetoolbar" content="no" />
+    <meta name="MSSmartTagsPreventParsing" content="true" />
+    <meta name="Copyright" content="(c) 2005 Copyright content:  Copyright design: Tobias Luetke" />
+    <!-- (c) Copyright 2005 by Tobias Luetke All Rights Reserved. -->
+  </head>
 
-	<body>
+  <body>
+    {% assign all_products = products | concat: more_products  %}
+    <h1>{{ description | split: '~' | first }}</h1>
 
-	  <h1>There are currently {{products | count}} products in the {{section}} catalog</h1>
+    <h2>{{ description | split: '~' | last }}</h2>
+
+    <h2>There are currently {{all_products | count}} products in the {{section}} catalog</h2>
 
     {% if cool_products %}
       Cool products :)
@@ -27,7 +31,7 @@
 
     <ul id="products">
 
-      {% for product in products %}
+      {% for product in all_products %}
         <li>
           <h2>{{product.name}}</h2>
           Only {{product.price | price }}
@@ -41,5 +45,5 @@
 
     </ul>
 
-	</body>
+  </body>
 </html>

init.rb

@@ -1,8 +0,0 @@
-require 'liquid'
-require 'extras/liquid_view'
-
-if defined? ActionView::Template and ActionView::Template.respond_to? :register_template_handler
-  ActionView::Template
-else
-  ActionView::Base
-end.register_template_handler(:liquid, LiquidView)

lib/extras/liquid_view.rb

@@ -1,51 +0,0 @@
-# LiquidView is a action view extension class. You can register it with rails
-# and use liquid as an template system for .liquid files
-#
-# Example
-# 
-#   ActionView::Base::register_template_handler :liquid, LiquidView
-class LiquidView
-  PROTECTED_ASSIGNS = %w( template_root response _session template_class action_name request_origin session template
-                          _response url _request _cookies variables_added _flash params _headers request cookies
-                          ignore_missing_templates flash _params logger before_filter_chain_aborted headers )
-  PROTECTED_INSTANCE_VARIABLES = %w( @_request @controller @_first_render @_memoized__pick_template @view_paths 
-                                     @helpers @assigns_added @template @_render_stack @template_format @assigns )
-  
-  def self.call(template)
-    "LiquidView.new(self).render(template, local_assigns)"
-  end
-
-  def initialize(view)
-    @view = view
-  end
-  
-  def render(template, local_assigns = nil)
-    @view.controller.headers["Content-Type"] ||= 'text/html; charset=utf-8'
-    
-    # Rails 2.2 Template has source, but not locals
-    if template.respond_to?(:source) && !template.respond_to?(:locals)
-      assigns = (@view.instance_variables - PROTECTED_INSTANCE_VARIABLES).inject({}) do |hash, ivar|
-                  hash[ivar[1..-1]] = @view.instance_variable_get(ivar)
-                  hash
-                end
-    else
-      assigns = @view.assigns.reject{ |k,v| PROTECTED_ASSIGNS.include?(k) }
-    end
-    
-    source = template.respond_to?(:source) ? template.source : template
-    local_assigns = (template.respond_to?(:locals) ? template.locals : local_assigns) || {}
-    
-    if content_for_layout = @view.instance_variable_get("@content_for_layout")
-      assigns['content_for_layout'] = content_for_layout
-    end
-    assigns.merge!(local_assigns.stringify_keys)
-    
-    liquid = Liquid::Template.parse(source)
-    liquid.render(assigns, :filters => [@view.controller.master_helper_module], :registers => {:action_view => @view, :controller => @view.controller})
-  end
-
-  def compilable?
-    false
-  end
-
-end

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
@@ -19,13 +21,12 @@
 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-$LOAD_PATH.unshift(File.dirname(__FILE__))
-
 module Liquid
   FilterSeparator             = /\|/
   ArgumentSeparator           = ','
   FilterArgumentSeparator     = ':'
   VariableAttributeSeparator  = '.'
+  WhitespaceControl           = '-'
   TagStart                    = /\{\%/
   TagEnd                      = /\%\}/
   VariableSignature           = /\(?[\w\-\.\[\]]\)?/
@@ -34,35 +35,58 @@ module Liquid
   VariableEnd                 = /\}\}/
   VariableIncompleteEnd       = /\}\}?/
   QuotedString                = /"[^"]*"|'[^']*'/
-  QuotedFragment              = /#{QuotedString}|(?:[^\s,\|'"]|#{QuotedString})+/
-  StrictQuotedFragment        = /"[^"]+"|'[^']+'|[^\s,\|,\:,\,]+/
-  FirstFilterArgument         = /#{FilterArgumentSeparator}(?:#{StrictQuotedFragment})/
-  OtherFilterArgument         = /#{ArgumentSeparator}(?:#{StrictQuotedFragment})/
-  SpacelessFilter             = /#{FilterSeparator}(?:#{StrictQuotedFragment})(?:#{FirstFilterArgument}(?:#{OtherFilterArgument})*)?/
-  Expression                  = /(?:#{QuotedFragment}(?:#{SpacelessFilter})*)/
-  TagAttributes               = /(\w+)\s*\:\s*(#{QuotedFragment})/
-  AnyStartingTag              = /\{\{|\{\%/
-  PartialTemplateParser       = /#{TagStart}.*?#{TagEnd}|#{VariableStart}.*?#{VariableIncompleteEnd}/
-  TemplateParser              = /(#{PartialTemplateParser}|#{AnyStartingTag})/
-  VariableParser              = /\[[^\]]+\]|#{VariableSegment}+\??/
+  QuotedFragment              = /#{QuotedString}|(?:[^\s,\|'"]|#{QuotedString})+/o
+  TagAttributes               = /(\w+)\s*\:\s*(#{QuotedFragment})/o
+  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/strainer'
+require 'liquid/interrupts'
+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'
 require 'liquid/variable'
+require 'liquid/variable_lookup'
+require 'liquid/range_lookup'
 require 'liquid/file_system'
+require 'liquid/resource_limits'
 require 'liquid/template'
-require 'liquid/htmltags'
 require 'liquid/standardfilters'
 require 'liquid/condition'
-require 'liquid/module_ex'
+require 'liquid/utils'
+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

@@ -1,101 +1,94 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   class Block < Tag
-    IsTag             = /^#{TagStart}/
-    IsVariable        = /^#{VariableStart}/
-    FullToken         = /^#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}$/
-    ContentOfVariable = /^#{VariableStart}(.*)#{VariableEnd}$/
+    MAX_DEPTH = 100
+
+    def initialize(tag_name, markup, options)
+      super
+      @blank = true
+    end
 
     def parse(tokens)
-      @nodelist ||= []
-      @nodelist.clear
-
-      while token = tokens.shift
-
-        case token
-        when IsTag
-          if token =~ FullToken
-
-            # if we found the proper block delimitor just end parsing here and let the outer block
-            # proceed
-            if block_delimiter == $1
-              end_tag
-              return
-            end
-
-            # fetch the tag from registered blocks
-            if tag = Template.tags[$1]
-              @nodelist << tag.new($1, $2, tokens)
-            else
-              # this tag is not registered with the system
-              # pass it to the current block for special handling or error reporting
-              unknown_tag($1, $2, tokens)
-            end
-          else
-            raise SyntaxError, "Tag '#{token}' was not properly terminated with regexp: #{TagEnd.inspect} "
-          end
-        when IsVariable
-          @nodelist << create_variable(token)
-        when ''
-          # pass
-        else
-          @nodelist << token
-        end
+      @body = new_body
+      while parse_body(@body, tokens)
       end
-
-      # Make sure that its ok to end parsing in the current block.
-      # Effectively this method will throw and exception unless the current block is
-      # of type Document
-      assert_missing_delimitation!
+      @body.freeze
     end
 
-    def end_tag
+    # For backwards compatibility
+    def render(context)
+      @body.render(context)
     end
 
-    def unknown_tag(tag, params, tokens)
-      case tag
-      when 'else'
-        raise SyntaxError, "#{block_name} tag does not expect else tag"
-      when 'end'
-        raise SyntaxError, "'end' is not a valid delimiter for #{block_name} tags. use #{block_delimiter}"
+    def blank?
+      @blank
+    end
+
+    def nodelist
+      @body.nodelist
+    end
+
+    def unknown_tag(tag_name, _markup, _tokenizer)
+      Block.raise_unknown_tag(tag_name, block_name, block_delimiter, parse_context)
+    end
+
+    # @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, "Unknown tag '#{tag}'"
+        raise SyntaxError, parse_context.locale.t("errors.syntax.unknown_tag", tag: tag)
       end
     end
 
-    def block_delimiter
-      "end#{block_name}"
+    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
 
-    def create_variable(token)
-      token.scan(ContentOfVariable) do |content|
-        return Variable.new(content.first)
+    def block_delimiter
+      @block_delimiter ||= "end#{block_name}"
+    end
+
+    private
+
+    # @api public
+    def new_body
+      parse_context.new_block_body
+    end
+
+    # @api public
+    def parse_body(body, tokens)
+      if parse_context.depth >= MAX_DEPTH
+        raise StackLevelError, "Nesting too deep"
       end
-      raise SyntaxError.new("Variable '#{token}' was not properly terminated with regexp: #{VariableEnd.inspect} ")
-    end
+      parse_context.depth += 1
+      begin
+        body.parse(tokens, parse_context) do |end_tag_name, end_tag_params|
+          @blank &&= body.blank?
 
-    def render(context)
-      render_all(@nodelist, context)
-    end
+          return false if end_tag_name == block_delimiter
+          raise_tag_never_closed(block_name) unless end_tag_name
 
-    protected
-
-    def assert_missing_delimitation!
-      raise SyntaxError.new("#{block_name} tag was never closed")
-    end
-
-    def render_all(list, context)
-      list.collect do |token|
-        begin
-          token.respond_to?(:render) ? token.render(context) : token
-        rescue Exception => e
-          context.handle_error(e)
+          # 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
+      ensure
+        parse_context.depth -= 1
       end
+
+      true
     end
   end
 end

lib/liquid/block_body.rb

@@ -0,0 +1,255 @@
+# frozen_string_literal: true
+
+require 'English'
+
+module Liquid
+  class BlockBody
+    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
+    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
+          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
+
+    # 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)
+      render_to_output_buffer(context, +'')
+    end
+
+    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
+          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
+        idx += 1
+
+        context.resource_limits.increment_write_score(output)
+      end
+
+      output
+    end
+
+    private
+
+    def render_node(context, output, node)
+      BlockBody.render_node(context, output, node)
+    end
+
+    def create_variable(token, parse_context)
+      token.scan(ContentOfVariable) do |content|
+        markup = content.first
+        return Variable.new(markup, parse_context)
+      end
+      BlockBody.raise_missing_variable_terminator(token, parse_context)
+    end
+
+    # @deprecated Use {.raise_missing_tag_terminator} instead
+    def raise_missing_tag_terminator(token, parse_context)
+      BlockBody.raise_missing_tag_terminator(token, parse_context)
+    end
+
+    # @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

@@ -1,55 +1,93 @@
+# frozen_string_literal: true
+
 module Liquid
   # Container for liquid nodes which conveniently wraps decision making logic
   #
   # Example:
   #
-  #   c = Condition.new('1', '==', '1')
+  #   c = Condition.new(1, '==', 1)
   #   c.evaluate #=> true
   #
   class Condition #:nodoc:
     @@operators = {
-      '==' => lambda { |cond, left, right|  cond.send(:equal_variables, left, right) },
-      '!=' => lambda { |cond, left, right| !cond.send(:equal_variables, left, right) },
-      '<>' => lambda { |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) },
+      '<>' => ->(cond, left, right) { !cond.send(:equal_variables, left, right) },
+      '<' => :<,
+      '>' => :>,
       '>=' => :>=,
       '<=' => :<=,
-      'contains' => lambda { |cond, left, right| left && right ? left.include?(right) : false }
+      '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, @operator, @right = left, operator, right
+      @left     = left
+      @operator = operator
+      @right    = right
+
       @child_relation  = nil
       @child_condition = nil
     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, @child_condition = :or, condition
+      @child_relation  = :or
+      @child_condition = condition
     end
 
     def and(condition)
-      @child_relation, @child_condition = :and, condition
+      @child_relation  = :and
+      @child_condition = condition
     end
 
     def attach(attachment)
@@ -64,20 +102,24 @@ module Liquid
       "#<Condition #{[@left, @operator, @right].compact.join(' ')}>"
     end
 
+    protected
+
+    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
@@ -90,31 +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[left] if op == nil
+      return context.evaluate(left) if op.nil?
 
-      left, right = context[left], context[right]
+      left  = context.evaluate(left)
+      right = context.evaluate(right)
 
-      operation = self.class.operators[op] || raise(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)
-        left.send(operation, right)
-      else
-        nil
+      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, e.message
+        end
+      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'
@@ -13,89 +14,142 @@ module Liquid
   #
   #   context['bob']  #=> nil  class Context
   class Context
-    attr_reader :scopes, :errors, :registers, :environments
+    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)
-      @environments   = [environments].flatten
-      @scopes         = [(outer_scope || {})]
-      @registers      = registers
-      @errors         = []
-      @rethrow_errors = rethrow_errors
+    # 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
+
+    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_renderer = Liquid::RAISE_EXCEPTION_LAMBDA
+      end
+
+      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)
+      @strainer ||= StrainerFactory.create(self, @filters)
     end
 
-    # adds filters to this context.
-    # this does not register the filters with the main Template object. see <tt>Template.register_filter</tt>
+    # Adds filters to this context.
+    #
+    # Note that this does not register the filters with the main Template object. see <tt>Template.register_filter</tt>
     # for that
     def add_filters(filters)
       filters = [filters].flatten.compact
-
-      filters.each do |f|
-        raise ArgumentError, "Expected module but got: #{f.class}" unless f.is_a?(Module)
-        strainer.extend(f)
-      end
+      @filters += filters
+      @strainer = nil
     end
 
-    def handle_error(e)
+    def apply_global_filter(obj)
+      global_filter.nil? ? obj : global_filter.call(obj)
+    end
+
+    # are there any not handled interrupts?
+    def interrupt?
+      !@interrupts.empty?
+    end
+
+    # push an interrupt to the stack. this interrupt is considered not handled.
+    def push_interrupt(e)
+      @interrupts.push(e)
+    end
+
+    # pop an interrupt from the stack
+    def pop_interrupt
+      @interrupts.pop
+    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 @rethrow_errors
-
-      case e
-      when SyntaxError
-        "Liquid syntax error: #{e.message}"
-      else
-        "Liquid error: #{e.message}"
-      end
+      exception_renderer.call(e).to_s
     end
 
-
     def invoke(method, *args)
-      if strainer.respond_to?(method)
-        strainer.__send__(method, *args)
-      else
-        args.first
-      end
+      strainer.invoke(method, *args).to_liquid
     end
 
-    # push new local scope on the stack. use <tt>Context#stack</tt> instead
-    def push(new_scope={})
-      raise StackLevelError, "Nesting too deep" if @scopes.length > 100
+    # Push new local scope on the stack. use <tt>Context#stack</tt> instead
+    def push(new_scope = {})
       @scopes.unshift(new_scope)
+      check_overflow
     end
 
-    # merge a hash of variables in the current local scope
+    # Merge a hash of variables in the current local scope
     def merge(new_scopes)
       @scopes[0].merge!(new_scopes)
     end
 
-    # pop from the stack. use <tt>Context#stack</tt> instead
+    # Pop from the stack. use <tt>Context#stack</tt> instead
     def pop
       raise ContextError if @scopes.size == 1
       @scopes.shift
     end
 
-    # pushes a new local scope on the stack, pops it at the end of the block
+    # Pushes a new local scope on the stack, pops it at the end of the block
     #
     # Example:
-    #
     #   context.stack do
     #      context['var'] = 'hi'
     #   end
-    #   context['var]  #=> nil
     #
-    def stack(new_scope={},&block)
-      result = nil
+    #   context['var]  #=> nil
+    def stack(new_scope = {})
       push(new_scope)
-      begin
-        result = yield
-      ensure
-        pop
+      yield
+    ensure
+      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
-      result
     end
 
     def clear_instance_assigns
@@ -107,148 +161,121 @@ module Liquid
       @scopes[0][key] = value
     end
 
-    def [](key)
-      resolve(key)
-    end
-
-    def has_key?(key)
-      resolve(key) != nil
-    end
-
-    private
-
     # Look up variable, either resolve directly after considering the name. We can directly handle
-    # Strings, digits, floats and booleans (true,false). If no match is made we lookup the variable in the current scope and
+    # Strings, digits, floats and booleans (true,false).
+    # If no match is made we lookup the variable in the current scope and
     # later move up to the parent blocks to see if we can resolve the variable somewhere up the tree.
     # Some special keywords return symbols. Those symbols are to be called on the rhs object in expressions
     #
     # Example:
-    #
     #   products == empty #=> products.empty?
-    #
-    def resolve(key)
-      case key
-      when nil, 'nil', 'null', ''
-        nil
-      when 'true'
-        true
-      when 'false'
-        false
-      when 'blank'
-        :blank?
-      when 'empty'
-        :empty?
-      # Single quoted strings
-      when /^'(.*)'$/
-        $1.to_s
-      # Double quoted strings
-      when /^"(.*)"$/
-        $1.to_s
-      # Integer and floats
-      when /^(\d+)$/
-        $1.to_i
-      # Ranges
-      when /^\((\S+)\.\.(\S+)\)$/
-        (resolve($1).to_i..resolve($2).to_i)
-      # Floats
-      when /^(\d[\d\.]+)$/
-        $1.to_f
+    def [](expression)
+      evaluate(Expression.parse(expression))
+    end
+
+    def key?(key)
+      self[key] != nil
+    end
+
+    def evaluate(object)
+      object.respond_to?(:evaluate) ? object.evaluate(self) : object
+    end
+
+    # Fetches an object starting at the local scope and then moving up the hierachy
+    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.key?(key) }
+
+      variable = if index
+        lookup_and_evaluate(@scopes[index], key, raise_on_not_found: raise_on_not_found)
       else
-        variable(key)
+        try_variable_find_in_environments(key, raise_on_not_found: raise_on_not_found)
       end
-    end
 
-    # fetches an object starting at the local scope and then moving up
-    # the hierachy
-    def find_variable(key)
-      scope = @scopes.find { |s| s.has_key?(key) }
-      if scope.nil?
-        @environments.each do |e|
-          if variable = lookup_and_evaluate(e, key)
-            scope = e
-            break
-          end
-        end
-      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
 
-    # resolves namespaced queries gracefully.
-    #
-    # Example
-    #
-    #  @context['hash'] = {"name" => 'tobi'}
-    #  assert_equal 'tobi', @context['hash.name']
-    #  assert_equal 'tobi', @context['hash["name"]']
-    #
-    def variable(markup)
-      parts = markup.scan(VariableParser)
-      square_bracketed = /^\[(.*)\]$/
-
-      first_part = parts.shift
-      if first_part =~ square_bracketed
-        first_part = resolve($1)
+    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
 
-      if object = find_variable(first_part)
+      value = obj[key]
 
-        parts.each do |part|
-          part = resolve($1) if part_resolved = (part =~ square_bracketed)
-
-          # 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?(:[]) and
-            ((object.respond_to?(:has_key?) and object.has_key?(part)) or
-             (object.respond_to?(:fetch) and part.is_a?(Integer)))
-
-            # if its a proc we will replace the entry with the proc
-            res = lookup_and_evaluate(object, part)
-            object = res.to_liquid
-
-          # Some special cases. If the part wasn't in square brackets and
-          # no key with the same name was found we interpret following calls
-          # as commands and call them on the current object
-          elsif !part_resolved and object.respond_to?(part) and ['size', 'first', 'last'].include?(part)
-
-            object = object.send(part.intern).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
-          else
-            return nil
-          end
-
-          # If we are dealing with a drop here we have to
-          object.context = self if object.respond_to?(:context=)
-        end
-      end
-
-      object
-    end
-    
-    def lookup_and_evaluate(obj, key)
-      if (value = obj[key]).is_a?(Proc) && obj.respond_to?(:[]=)
-        obj[key] = value.call(self)
+      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
+
+    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.has_key?(k)
+          if env.key?(k)
             scopes.last[k] = lookup_and_evaluate(env, k)
             break
           end
         end
       end
-    end
-    
-  end
-end
+    end # squash_instance_assigns_with_environments
+  end # Context
+end # Liquid

lib/liquid/document.rb

@@ -1,17 +1,65 @@
+# frozen_string_literal: true
+
 module Liquid
-  class Document < Block
-    # we don't need markup to open this block
-    def initialize(tokens)
-      parse(tokens)
+  class Document
+    def self.parse(tokens, parse_context)
+      doc = new(parse_context)
+      doc.parse(tokens, parse_context)
+      doc
     end
 
-    # There isn't a real delimter
-    def block_delimiter
-      []
+    attr_reader :parse_context, :body
+
+    def initialize(parse_context)
+      @parse_context = parse_context
+      @body = new_body
     end
 
-    # Document blocks don't need to be terminated since they are not actually opened
-    def assert_missing_delimitation!
+    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 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
 end

lib/liquid/drop.rb

@@ -1,51 +1,80 @@
-module Liquid
+# frozen_string_literal: true
 
-  # A drop in liquid is a class which allows you to to export DOM like things to liquid
+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 the implement lazy loaded objects.
+  # The main use for liquid drops is to implement lazy loaded objects.
   # If you would like to make data available to the web designers which you don't want loaded unless needed then
-  # a drop is a great way to do that
+  # a drop is a great way to do that.
   #
   # Example:
   #
-  # class ProductDrop < Liquid::Drop
-  #   def top_sales
-  #      Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
+  #   class ProductDrop < Liquid::Drop
+  #     def top_sales
+  #       Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
+  #     end
   #   end
-  # end
   #
-  # tmpl = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {%endfor%} '  )
-  # tmpl.render('product' => ProductDrop.new ) # will invoke top_sales query.
+  #   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
 
     # 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)
-      # for backward compatibility with Ruby 1.8
-      methods = self.class.public_instance_methods.map { |m| m.to_s }
-      if methods.include?(method.to_s)
-        send(method.to_sym)
+    def invoke_drop(method_or_key)
+      if self.class.invokable?(method_or_key)
+        send(method_or_key)
       else
-        before_method(method)
+        liquid_method_missing(method_or_key)
       end
     end
 
-    def has_key?(name)
+    def key?(_name)
       true
     end
 
+    def inspect
+      self.class.to_s
+    end
+
     def to_liquid
       self
     end
 
-    alias :[] :invoke_drop
+    def to_s
+      self.class.name
+    end
+
+    alias_method :[], :invoke_drop
+
+    # Check for method existence without invoking respond_to?, which creates symbols
+    def self.invokable?(method_name)
+      invokable_methods.include?(method_name.to_s)
+    end
+
+    def self.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]
+        end
+
+        whitelist = [:to_liquid] + (public_instance_methods - blacklist)
+        Set.new(whitelist.map(&:to_s))
+      end
+    end
   end
 end

lib/liquid/errors.rb

@@ -1,11 +1,58 @@
-module Liquid
-  class Error < ::StandardError; end
+# frozen_string_literal: true
 
-  class ArgumentError < Error; end
-  class ContextError < Error; end
-  class FilterNotFound < Error; end
-  class FileSystemError < Error; end
-  class StandardError < Error; end
-  class SyntaxError < Error; end
-  class StackLevelError < Error; end
+module Liquid
+  class Error < ::StandardError
+    attr_accessor :line_number
+    attr_accessor :template_name
+    attr_accessor :markup_context
+
+    def to_s(with_prefix = true)
+      str = +""
+      str << message_prefix if with_prefix
+      str << super()
+
+      if markup_context
+        str << " "
+        str << markup_context
+      end
+
+      str
+    end
+
+    private
+
+    def message_prefix
+      str = +""
+      str << if is_a?(SyntaxError)
+        "Liquid syntax error"
+      else
+        "Liquid error"
+      end
+
+      if line_number
+        str << " ("
+        str << template_name << " " if template_name
+        str << "line " << line_number.to_s << ")"
+      end
+
+      str << ": "
+      str
+    end
+  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

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Expression
+    LITERALS = {
+      nil => nil, 'nil' => nil, 'null' => nil, '' => nil,
+      'true' => true,
+      'false' => false,
+      'blank' => '',
+      'empty' => ''
+    }.freeze
+
+    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)
+      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
+        markup = markup.strip
+        if LITERALS.key?(markup)
+          LITERALS[markup]
+        else
+          VariableLookup.parse(markup)
+        end
+      end
+    end
+  end
+end

lib/liquid/extensions.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'time'
 require 'date'
 
@@ -7,50 +9,68 @@ 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
 
-def true.to_liquid  # :nodoc:
-  self
+class Date # :nodoc:
+  def to_liquid
+    self
+  end
 end
 
-def false.to_liquid # :nodoc:
-  self
+class TrueClass
+  def to_liquid # :nodoc:
+    self
+  end
 end
 
-def nil.to_liquid # :nodoc:
-  self
+class FalseClass
+  def to_liquid # :nodoc:
+    self
+  end
+end
+
+class NilClass
+  def to_liquid # :nodoc:
+    self
+  end
 end

lib/liquid/file_system.rb

@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 module Liquid
-  # A Liquid file system is way to let your templates retrieve other templates for use with the include tag.
+  # A Liquid file system is a way to let your templates retrieve other templates for use with the include tag.
   #
   # You can implement subclasses that retrieve templates from the database, from the file system using a different
   # path structure, you can provide them as hard-coded inline strings, or any manner that you see fit.
@@ -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
@@ -26,35 +28,46 @@ 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.
+  # Default pattern is "_%s.liquid".
+  #
+  # Example:
+  #
+  #   file_system = Liquid::LocalFileSystem.new("/some/path", "%s.html")
+  #
+  #   file_system.full_path("index") # => "/some/path/index.html"
   #
   class LocalFileSystem
     attr_accessor :root
 
-    def initialize(root)
-      @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-zA-Z0-9_\/]+$/
+      raise FileSystemError, "Illegal template name '#{template_path}'" unless %r{\A[^./][a-zA-Z0-9_/]+\z}.match?(template_path)
 
       full_path = if template_path.include?('/')
-        File.join(root, File.dirname(template_path), "_#{File.basename(template_path)}.liquid")
+        File.join(root, File.dirname(template_path), @pattern % File.basename(template_path))
       else
-        File.join(root, "_#{template_path}.liquid")
+        File.join(root, @pattern % template_path)
       end
 
-      raise FileSystemError, "Illegal template path '#{File.expand_path(full_path)}'" unless File.expand_path(full_path) =~ /^#{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/htmltags.rb

@@ -1,74 +0,0 @@
-module Liquid
-  class TableRow < Block
-    Syntax = /(\w+)\s+in\s+(#{VariableSignature}+)/
-
-    def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
-        @variable_name = $1
-        @collection_name = $2
-        @attributes = {}
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = value
-        end
-      else
-        raise SyntaxError.new("Syntax Error in 'table_row loop' - Valid syntax: table_row [item] in [collection] cols=3")
-      end
-
-      super
-    end
-
-    def render(context)
-      collection = context[@collection_name] or return ''
-
-      if @attributes['limit'] or @attributes['offset']
-        limit = context[@attributes['limit']] || -1
-        offset = context[@attributes['offset']] || 0
-        collection = collection[offset.to_i..(limit.to_i + offset.to_i - 1)]
-      end
-
-      length = collection.length
-
-      cols = context[@attributes['cols']].to_i
-
-      row = 1
-      col = 0
-
-      result = ["<tr class=\"row1\">\n"]
-      context.stack do
-
-        collection.each_with_index do |item, index|
-          context[@variable_name] = item
-          context['tablerowloop'] = {
-            'length'  => length,
-            'index'   => index + 1,
-            'index0'  => index,
-            'col'     => col + 1,
-            'col0'    => col,
-            'index0'  => index,
-            'rindex'  => length - index,
-            'rindex0' => length - index -1,
-            'first'   => (index == 0),
-            'last'    => (index == length - 1),
-            'col_first' => (col == 0),
-            'col_last'  => (col == cols - 1)
-          }
-
-
-          col += 1
-
-          result << ["<td class=\"col#{col}\">"] + render_all(@nodelist, context) + ['</td>']
-
-          if col == cols and not (index == length - 1)
-            col  = 0
-            row += 1
-            result << ["</tr>\n<tr class=\"row#{row}\">"]
-          end
-
-        end
-      end
-      result + ["</tr>\n"]
-    end
-  end
-
-  Template.register_tag('tablerow', TableRow)
-end

lib/liquid/i18n.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'yaml'
+
+module Liquid
+  class I18n
+    DEFAULT_LOCALE = File.join(File.expand_path(__dir__), "locales", "en.yml")
+
+    TranslationError = Class.new(StandardError)
+
+    attr_reader :path
+
+    def initialize(path = DEFAULT_LOCALE)
+      @path = path
+    end
+
+    def translate(name, vars = {})
+      interpolate(deep_fetch_translation(name), vars)
+    end
+    alias_method :t, :translate
+
+    def locale
+      @locale ||= YAML.load_file(@path)
+    end
+
+    private
+
+    def interpolate(name, vars)
+      name.gsub(/%\{(\w+)\}/) do
+        # raise TranslationError, "Undefined key #{$1} for interpolation in translation #{name}"  unless vars[$1.to_sym]
+        (vars[Regexp.last_match(1).to_sym]).to_s
+      end
+    end
+
+    def deep_fetch_translation(name)
+      name.split('.').reduce(locale) do |level, cur|
+        level[cur] || raise(TranslationError, "Translation for #{name} does not exist in locale #{path}")
+      end
+    end
+  end
+end

lib/liquid/interrupts.rb

@@ -0,0 +1,18 @@
+# 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"
+    end
+  end
+
+  # Interrupt that is thrown whenever a {% break %} is called.
+  class BreakInterrupt < Interrupt; end
+
+  # Interrupt that is thrown whenever a {% continue %} is called.
+  class ContinueInterrupt < Interrupt; end
+end

lib/liquid/lexer.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require "strscan"
+module Liquid
+  class Lexer
+    SPECIALS = {
+      '|' => :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(?=\s)/
+    WHITESPACE_OR_NOTHING = /\s*/
+
+    def initialize(input)
+      @ss = StringScanner.new(input)
+    end
+
+    def tokenize
+      @output = []
+
+      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]
+          else
+            raise SyntaxError, "Unexpected character #{c}"
+          end
+        end
+        @output << tok
+      end
+
+      @output << [:end_of_string]
+    end
+  end
+end

lib/liquid/locales/en.yml

@@ -0,0 +1,29 @@
+---
+  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]"
+      case_invalid_when: "Syntax Error in tag 'case' - Valid when condition: {% when [condition] [or condition2...] %}"
+      case_invalid_else: "Syntax Error in tag 'case' - Valid else condition: {% else %} (no parameters) "
+      cycle: "Syntax Error in 'cycle' - Valid syntax: cycle [name :] var [, var2, var3 ...]"
+      for: "Syntax Error in 'for loop' - Valid syntax: for [item] in [collection]"
+      for_invalid_in: "For loops require an 'in' clause"
+      for_invalid_attribute: "Invalid attribute in for loop. Valid attributes are limit and offset"
+      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: "'%{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"
+      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"
+      inline_comment_invalid: "Syntax error in tag '#' - Each line of comments must be prefixed by the '#' character"
+    argument:
+      include: "Argument error in tag 'include' - Illegal template name"
+    disabled:
+      tag: "usage is not allowed in this context"

lib/liquid/module_ex.rb

@@ -1,62 +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 usesd 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
-# 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

@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Parser
+    def initialize(input)
+      l       = Lexer.new(input)
+      @tokens = l.tokenize
+      @p      = 0 # pointer to current location
+    end
+
+    def jump(point)
+      @p = point
+    end
+
+    def consume(type = nil)
+      token = @tokens[@p]
+      if type && token[0] != type
+        raise SyntaxError, "Expected #{type} but found #{@tokens[@p].first}"
+      end
+      @p += 1
+      token[1]
+    end
+
+    # Only consumes the token if it matches the type
+    # Returns the token's contents if it was consumed
+    # or false otherwise.
+    def consume?(type)
+      token = @tokens[@p]
+      return false unless token && token[0] == type
+      @p += 1
+      token[1]
+    end
+
+    # Like consume? Except for an :id token of a certain name
+    def id?(str)
+      token = @tokens[@p]
+      return false unless token && token[0] == :id
+      return false unless token[1] == str
+      @p += 1
+      token[1]
+    end
+
+    def look(type, ahead = 0)
+      tok = @tokens[@p + ahead]
+      return false unless tok
+      tok[0] == type
+    end
+
+    def expression
+      token = @tokens[@p]
+      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
+      when :open_round
+        consume
+        first = expression
+        consume(:dotdot)
+        last = expression
+        consume(:close_round)
+        "(#{first}..#{last})"
+      else
+        raise SyntaxError, "#{token} is not a valid expression"
+      end
+    end
+
+    def argument
+      str = +""
+      # might be a keyword argument (identifier: expression)
+      if look(:id) && look(:colon, 1)
+        str << consume << consume << ' '
+      end
+
+      str << expression
+      str
+    end
+
+    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
+  end
+end

lib/liquid/parser_switching.rb

@@ -0,0 +1,45 @@
+# 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 parse_context.error_mode
+      when :strict then strict_parse_with_error_context(markup)
+      when :lax    then lax_parse(markup)
+      when :warn
+        begin
+          strict_parse_with_error_context(markup)
+        rescue SyntaxError => e
+          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
+
+    def markup_context(markup)
+      "in \"#{markup.strip}\""
+    end
+  end
+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

@@ -0,0 +1,139 @@
+# 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'.
+  # Then, to profile a parse/render cycle, pass the <tt>profile: true</tt> option to <tt>Liquid::Template.parse</tt>.
+  # After <tt>Liquid::Template#render</tt> is called, the template object makes available an instance of this
+  # class via the <tt>Liquid::Template#profiler</tt> method.
+  #
+  #   template = Liquid::Template.parse(template_content, profile: true)
+  #   output  = template.render
+  #   profile = template.profiler
+  #
+  # This object contains all profiling information, containing information on what tags were rendered,
+  # where in the templates these tags live, and how long each tag took to render.
+  #
+  # This is a tree structure that is Enumerable all the way down, and keeps track of tags and rendering times
+  # inside of <tt>{% include %}</tt> tags.
+  #
+  #   profile.each do |node|
+  #     # Access to the node itself
+  #     node.code
+  #
+  #     # Which template and line number of this node.
+  #     # The top-level template name is `nil` by default, but can be set in the Liquid::Context before rendering.
+  #     node.partial
+  #     node.line_number
+  #
+  #     # Render time in seconds of this node
+  #     node.render_time
+  #
+  #     # If the template used {% include %}, this node will also have children.
+  #     node.children.each do |child2|
+  #       # ...
+  #     end
+  #   end
+  #
+  # Profiler also exposes the total time of the template's render in <tt>Liquid::Profiler#total_render_time</tt>.
+  #
+  # All render times are in seconds. There is a small performance hit when profiling is enabled.
+  #
+  class Profiler
+    include Enumerable
+
+    class Timing
+      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(code: nil, template_name: nil, line_number: nil)
+        @code = code
+        @template_name = template_name
+        @line_number = line_number
+        @children = []
+      end
+
+      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
+    end
+
+    attr_reader :total_time
+    alias_method :total_render_time, :total_time
+
+    def initialize
+      @root_children = []
+      @current_children = nil
+      @total_time = 0.0
+    end
+
+    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 children
+      children = @root_children
+      if children.length == 1
+        children.first.children
+      else
+        children
+      end
+    end
+
+    def each(&block)
+      children.each(&block)
+    end
+
+    def [](idx)
+      children[idx]
+    end
+
+    def length
+      children.length
+    end
+
+    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
+
+    private
+
+    def monotonic_time
+      Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    end
+  end
+end

lib/liquid/profiler/hooks.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Liquid
+  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
+  end
+  BlockBody.prepend(BlockBodyProfilingHook)
+
+  module DocumentProfilingHook
+    def render_to_output_buffer(context, output)
+      return super unless context.profiler
+      context.profiler.profile(context.template_name) { super }
+    end
+  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

@@ -0,0 +1,39 @@
+# 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)
+      if start_obj.respond_to?(:evaluate) || end_obj.respond_to?(:evaluate)
+        new(start_obj, end_obj)
+      else
+        start_obj.to_i..end_obj.to_i
+      end
+    end
+
+    def initialize(start_obj, end_obj)
+      @start_obj = start_obj
+      @end_obj   = end_obj
+    end
+
+    def evaluate(context)
+      start_int = to_integer(context.evaluate(@start_obj))
+      end_int   = to_integer(context.evaluate(@end_obj))
+      start_int..end_int
+    end
+
+    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

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module Liquid
+  class ResourceLimits
+    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]
+      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?
+      @reached_limit
+    end
+
+    def reset
+      @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

@@ -1,21 +1,36 @@
+# frozen_string_literal: true
+
 require 'cgi'
+require 'bigdecimal'
 
 module Liquid
-  
   module StandardFilters
+    HTML_ESCAPE = {
+      '&' => '&',
+      '>' => '>',
+      '<' => '&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)
-      
       input.respond_to?(:size) ? input.size : 0
     end
 
-    # convert a input string to DOWNCASE
+    # convert an input string to DOWNCASE
     def downcase(input)
       input.to_s.downcase
     end
 
-    # convert a input string to UPCASE
+    # convert an input string to UPCASE
     def upcase(input)
       input.to_s.upcase
     end
@@ -26,83 +41,241 @@ module Liquid
     end
 
     def escape(input)
-      CGI.escapeHTML(input) rescue input
+      CGI.escapeHTML(input.to_s) unless input.nil?
+    end
+    alias_method :h, :escape
+
+    def escape_once(input)
+      input.to_s.gsub(HTML_ESCAPE_ONCE_REGEXP, HTML_ESCAPE)
     end
 
-    alias_method :h, :escape
+    def url_encode(input)
+      CGI.escape(input.to_s) unless input.nil?
+    end
+
+    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) || []
+      else
+        input.to_s.slice(offset, length) || ''
+      end
+    end
 
     # Truncate a string down to x characters
     def truncate(input, length = 50, truncate_string = "...")
-      if input.nil? then return end
-      l = length.to_i - truncate_string.length
+      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 = "...")
-      if input.nil? then return end
-      wordlist = input.to_s.split
-      l = words.to_i - 1
-      l = 0 if l < 0
-      wordlist.length > l ? wordlist[0..l].join(" ") + truncate_string : input 
+      return if input.nil?
+      input = input.to_s
+      words = Utils.to_integer(words)
+      words = 1 if words <= 0
+
+      wordlist = input.split(" ", words + 1)
+      return input if wordlist.length <= words
+
+      wordlist.pop
+      wordlist.join(" ").concat(truncate_string.to_s)
+    end
+
+    # Split input string into an array of substrings separated by given pattern.
+    #
+    # Example:
+    #   <div class="summary">{{ post | split '//' | first }}</div>
+    #
+    def split(input, pattern)
+      input.to_s.split(pattern.to_s)
+    end
+
+    def strip(input)
+      input.to_s.strip
+    end
+
+    def lstrip(input)
+      input.to_s.lstrip
+    end
+
+    def rstrip(input)
+      input.to_s.rstrip
     end
 
     def strip_html(input)
-      input.to_s.gsub(/<script.*?<\/script>/, '').gsub(/<.*?>/, '')
+      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(/\n/, '')      
+      input.to_s.gsub(/\r?\n/, '')
     end
 
-    
     # Join elements of the array with certain character between them
     def join(input, glue = ' ')
-      [input].flatten.join(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 = [input].flatten
+      ary = InputIterator.new(input, context)
+
+      return [] if ary.empty?
+
       if property.nil?
-        ary.sort
-      elsif ary.first.respond_to?('[]') and !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, context)
+
+      return [] if ary.empty?
+
+      if property.nil?
+        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, context)
+
+      if property.nil?
+        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, context)
+      ary.reverse
+    end
+
     # map/collect on a given property
     def map(input, property)
-      ary = [input].flatten
-      if ary.first.respond_to?('[]') and !ary.first[property].nil?
-        ary.map {|e| e[property] }
-      elsif ary.first.respond_to?(property)
-        ary.map {|e| e.send(property) }
+      InputIterator.new(input, context).map do |e|
+        e = e.call if e.is_a?(Proc)
+
+        if property == "to_liquid"
+          e
+        elsif e.respond_to?(:[])
+          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 = '')
-      input.to_s.gsub(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 = '')
-      input.to_s.sub(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, '')      
+      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, '')      
+      input.to_s.sub(string.to_s, '')
     end
 
     # add one string to another
@@ -110,6 +283,13 @@ module Liquid
       input.to_s + string.to_s
     end
 
+    def concat(input, 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
     def prepend(input, string)
       string.to_s + input.to_s
@@ -117,10 +297,10 @@ 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")      
+      input.to_s.gsub(/\r?\n/, "<br />\n")
     end
 
-    # Reformat a date
+    # Reformat a date using Ruby's core Time#strftime( string ) -> string
     #
     #   %a - The abbreviated weekday name (``Sun'')
     #   %A - The  full  weekday  name (``Sunday'')
@@ -134,6 +314,7 @@ module Liquid
     #   %m - Month of the year (01..12)
     #   %M - Minute of the hour (00..59)
     #   %p - Meridian indicator (``AM''  or  ``PM'')
+    #   %s - Number of seconds since 1970-01-01 00:00:00 UTC.
     #   %S - Second of the minute (00..60)
     #   %U - Week  number  of the current year,
     #           starting with the first Sunday as the first
@@ -148,21 +329,14 @@ module Liquid
     #   %Y - Year with century
     #   %Z - Time zone name
     #   %% - Literal ``%'' character
+    #
+    #   See also: http://www.ruby-doc.org/core/Time.html#method-i-strftime
     def date(input, format)
+      return input if format.to_s.empty?
 
-      if format.to_s.empty?
-        return input.to_s
-      end
+      return input unless (date = Utils.to_date(input))
 
-      date = input.is_a?(String) ? Time.parse(input) : input
-      
-      if date.respond_to?(:strftime)
-        date.strftime(format.to_s)
-      else
-        input
-      end
-    rescue => e 
-      input
+      date.strftime(format.to_s)
     end
 
     # Get the first element of the passed in array
@@ -183,39 +357,170 @@ 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)
-      to_number(input) + to_number(operand)
+      apply_operation(input, operand, :+)
     end
 
     # subtraction
     def minus(input, operand)
-      to_number(input) - to_number(operand)
+      apply_operation(input, operand, :-)
     end
 
     # multiplication
     def times(input, operand)
-      to_number(input) * to_number(operand)
+      apply_operation(input, operand, :*)
     end
 
     # division
     def divided_by(input, operand)
-      to_number(input) / to_number(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 = 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)
+      Utils.to_number(input).ceil.to_i
+    rescue ::FloatDomainError => e
+      raise Liquid::FloatDomainError, e.message
+    end
+
+    def floor(input)
+      Utils.to_number(input).floor.to_i
+    rescue ::FloatDomainError => e
+      raise Liquid::FloatDomainError, e.message
+    end
+
+    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 Numeric
-        obj
-      when String
-        (obj.strip =~ /^\d+\.\d+$/) ? obj.to_f : obj.to_i
+    attr_reader :context
+
+    def raise_property_error(property)
+      raise Liquid::ArgumentError, "cannot select the property '#{property}'"
+    end
+
+    def apply_operation(input, operand, operation)
+      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
-        0
+        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, context)
+        @context = context
+        @input   = if input.is_a?(Array)
+          input.flatten
+        elsif input.is_a?(Hash)
+          [input]
+        elsif input.is_a?(Enumerable)
+          input
+        else
+          Array(input)
+        end
+      end
+
+      def join(glue)
+        to_a.join(glue.to_s)
+      end
+
+      def 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
+    end
   end
 
   Template.register_filter(StandardFilters)

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

@@ -1,51 +0,0 @@
-require 'set'
-
-module Liquid
-
-  parent_object = if defined? BlankObject
-    BlankObject
-  else
-    Object
-  end
-
-  # Strainer is the parent class for the filters system.
-  # New filters are mixed into the strainer class which is then instanciated for each liquid template render run.
-  #
-  # One of the strainer's responsibilities is to keep malicious method calls out
-  class Strainer < parent_object #:nodoc:
-    INTERNAL_METHOD = /^__/
-    @@required_methods = Set.new([:__id__, :__send__, :respond_to?, :extend, :methods, :class, :object_id])
-
-    @@filters = {}
-
-    def initialize(context)
-      @context = context
-    end
-
-    def self.global_filter(filter)
-      raise ArgumentError, "Passed filter is not a module" unless filter.is_a?(Module)
-      @@filters[filter.name] = filter
-    end
-
-    def self.create(context)
-      strainer = Strainer.new(context)
-      @@filters.each { |k,m| strainer.extend(m) }
-      strainer
-    end
-
-    def respond_to?(method, include_private = false)
-      method_name = method.to_s
-      return false if method_name =~ INTERNAL_METHOD
-      return false if @@required_methods.include?(method_name)
-      super
-    end
-
-    # remove all standard methods from the bucket so circumvent security
-    # problems
-    instance_methods.each do |m|
-      unless @@required_methods.include?(m.to_sym)
-        undef_method m
-      end
-    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

@@ -1,26 +1,65 @@
+# frozen_string_literal: true
+
 module Liquid
-
   class Tag
-    attr_accessor :nodelist
+    attr_reader :nodelist, :tag_name, :line_number, :parse_context
+    alias_method :options, :parse_context
+    include ParserSwitching
 
-    def initialize(tag_name, markup, tokens)
-      @tag_name   = tag_name
-      @markup     = markup
-      parse(tokens)
+    class << self
+      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 parse(tokens)
+    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)
+    end
+
+    def raw
+      "#{@tag_name} #{@markup}"
     end
 
     def name
       self.class.name.downcase
     end
 
-    def render(context)
+    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
+
+    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' %}
@@ -9,24 +10,63 @@ module Liquid
   #  {{ foo }}
   #
   class Assign < Tag
-    Syntax = /(#{VariableSignature}+)\s*=\s*(#{QuotedFragment}+)/   
+    Syntax = /(#{VariableSignature}+)\s*=\s*(.*)\s*/om
 
-    def initialize(tag_name, markup, tokens)          
-      if markup =~ Syntax
-        @to = $1
-        @from = $2
-      else
-        raise SyntaxError.new("Syntax Error in 'assign' - Valid syntax: assign [var] = [source]")
-      end
+    # @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   = Regexp.last_match(1)
+        @from = Variable.new(Regexp.last_match(2), parse_context)
+      else
+        self.class.raise_syntax_error(parse_context)
+      end
     end
 
-    def render(context)
-       context.scopes.last[@to] = context[@from]
-       ''
+    def render_to_output_buffer(context, output)
+      val = @from.render(context)
+      context.scopes.last[@to] = val
+      context.resource_limits.increment_assign_score(assign_score_of(val))
+      output
     end
 
+    def blank?
+      true
+    end
+
+    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', Assign)

lib/liquid/tags/break.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Liquid
+  # Break tag to be used to break out of a for loop.
+  #
+  # == Basic Usage:
+  #    {% for item in collection %}
+  #      {% if item.condition %}
+  #        {% break %}
+  #      {% endif %}
+  #    {% endfor %}
+  #
+  class Break < Tag
+    INTERRUPT = BreakInterrupt.new.freeze
+
+    def render_to_output_buffer(context, output)
+      context.push_interrupt(INTERRUPT)
+      output
+    end
+  end
+
+  Template.register_tag('break', Break)
+end

lib/liquid/tags/capture.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Capture stores the result of a block into a variable without rendering it inplace.
   #
   #   {% capture heading %}
@@ -12,22 +13,27 @@ module Liquid
   # in a sidebar or footer.
   #
   class Capture < Block
-    Syntax = /(\w+)/
-
-    def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
-        @to = $1
-      else
-        raise SyntaxError.new("Syntax Error in 'capture' - Valid syntax: capture [var]")
-      end
+    Syntax = /(#{VariableSignature}+)/o
 
+    def initialize(tag_name, markup, options)
       super
+      if markup =~ Syntax
+        @to = Regexp.last_match(1)
+      else
+        raise SyntaxError, options[:locale].t("errors.syntax.capture")
+      end
     end
 
-    def render(context)
-      output = super
-      context.scopes.last[@to] = output.join
-      ''
+    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
   end
 

lib/liquid/tags/case.rb

@@ -1,22 +1,41 @@
+# frozen_string_literal: true
+
 module Liquid
   class Case < Block
-    Syntax     = /(#{QuotedFragment})/
-    WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/
+    Syntax     = /(#{QuotedFragment})/o
+    WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/om
 
-    def initialize(tag_name, markup, tokens)      
+    attr_reader :blocks, :left
+
+    def initialize(tag_name, markup, options)
+      super
       @blocks = []
 
       if markup =~ Syntax
-        @left = $1
+        @left = parse_expression(Regexp.last_match(1))
       else
-        raise SyntaxError.new("Syntax Error in tag 'case' - Valid syntax: case [condition]")
+        raise SyntaxError, options[:locale].t("errors.syntax.case")
       end
+    end
 
-      super
+    def parse(tokens)
+      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
+      @blocks.map(&:attachment)
     end
 
     def unknown_tag(tag, markup, tokens)
-      @nodelist = []
       case tag
       when 'when'
         record_when_condition(markup)
@@ -27,56 +46,54 @@ module Liquid
       end
     end
 
-    def render(context)      
-      context.stack do          
-        execute_else_block = true
+    def render_to_output_buffer(context, output)
+      execute_else_block = true
 
-        @blocks.inject([]) do |output, block|
-      
-          if block.else? 
-            
-            return render_all(block.attachment, context) if execute_else_block
-            
-          elsif block.evaluate(context)
-            
-            execute_else_block = false        
-            output += render_all(block.attachment, context)                    
-          end            
-      
-          output
+      @blocks.each do |block|
+        if block.else?
+          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
       end
+
+      output
     end
 
     private
 
     def record_when_condition(markup)
+      body = new_body
+
       while markup
-      	# Create a new nodelist and assign it to the new block
-      	if not markup =~ WhenSyntax
-      	  raise SyntaxError.new("Syntax Error in tag 'case' - Valid when condition: {% when [condition] [or condition2...] %} ")
-      	end
+        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, '==', $1)        
-      	block.attach(@nodelist)
-      	@blocks.push(block)
+        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("Syntax Error in tag 'case' - Valid else condition: {% else %} (no parameters) ")
+      unless markup.strip.empty?
+        raise SyntaxError, options[:locale].t("errors.syntax.case_invalid_else")
       end
 
       block = ElseCondition.new
-      block.attach(@nodelist)
+      block.attach(new_body)
       @blocks << block
     end
 
-        
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [@node.left] + @node.blocks
+      end
+    end
   end
 
   Template.register_tag('case', Case)

lib/liquid/tags/comment.rb

@@ -1,7 +1,16 @@
+# frozen_string_literal: true
+
 module Liquid
   class Comment < Block
-    def render(context)
-      ''
+    def render_to_output_buffer(_context, output)
+      output
+    end
+
+    def unknown_tag(_tag, _markup, _tokens)
+    end
+
+    def blank?
+      true
     end
   end
 

lib/liquid/tags/continue.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Liquid
+  # Continue tag to be used to break out of a for loop.
+  #
+  # == Basic Usage:
+  #    {% for item in collection %}
+  #      {% if item.condition %}
+  #        {% continue %}
+  #      {% endif %}
+  #    {% endfor %}
+  #
+  class Continue < Tag
+    INTERRUPT = ContinueInterrupt.new.freeze
+
+    def render_to_output_buffer(context, output)
+      context.push_interrupt(INTERRUPT)
+      output
+    end
+  end
+
+  Template.register_tag('continue', Continue)
+end

lib/liquid/tags/cycle.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Cycle is usually used within a loop to alternate between values, like colors or DOM classes.
   #
   #   {% for item in items %}
@@ -13,46 +14,62 @@ module Liquid
   #    <div class="green"> Item five</div>
   #
   class Cycle < Tag
-    SimpleSyntax = /^#{QuotedFragment}+/        
-    NamedSyntax  = /^(#{QuotedFragment})\s*\:\s*(.*)/
+    SimpleSyntax = /\A#{QuotedFragment}+/o
+    NamedSyntax  = /\A(#{QuotedFragment})\s*\:\s*(.*)/om
 
-    def initialize(tag_name, markup, tokens)      
+    attr_reader :variables
+
+    def initialize(tag_name, markup, options)
+      super
       case markup
       when NamedSyntax
-      	@variables = variables_from_string($2)
-      	@name = $1
+        @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("Syntax Error in 'cycle' - Valid syntax: cycle [name :] var [, var2, var3 ...]")
+        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
       end
-      super    
     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[@name]	
-        iteration = context.registers[:cycle][key]
-        result = context[@variables[iteration]]
-        iteration += 1    
-        iteration  = 0  if iteration >= @variables.size 
-        context.registers[:cycle][key] = iteration
-        result 
+      key       = context.evaluate(@name)
+      iteration = context.registers[:cycle][key].to_i
+
+      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
 
     def variables_from_string(markup)
       markup.split(',').collect do |var|
-    	  var =~ /\s*(#{QuotedFragment})\s*/
-    	  $1 ? $1 : nil
-    	end.compact
+        var =~ /\s*(#{QuotedFragment})\s*/o
+        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

@@ -0,0 +1,38 @@
+# 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.
+  #     NOTE: decrement is a pre-decrement, --i,
+  #           while increment is post:      i++.
+  #
+  #     (To achieve the survival, the application must keep the context)
+  #
+  #     if the variable does not exist, it is created with value 0.
+
+  #   Hello: {% decrement variable %}
+  #
+  # gives you:
+  #
+  #    Hello: -1
+  #    Hello: -2
+  #    Hello: -3
+  #
+  class Decrement < Tag
+    def initialize(tag_name, markup, options)
+      super
+      @variable = markup.strip
+    end
+
+    def render_to_output_buffer(context, output)
+      value = context.environments.first[@variable] ||= 0
+      value -= 1
+      context.environments.first[@variable] = value
+      output << value.to_s
+      output
+    end
+  end
+
+  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.
   #
@@ -13,6 +14,8 @@ module Liquid
   #      <div {% if forloop.first %}class="first"{% endif %}>
   #        Item {{ forloop.index }}: {{ item.name }}
   #      </div>
+  #    {% else %}
+  #      There is nothing in the collection.
   #    {% endfor %}
   #
   # You can also define a limit and offset much like SQL.  Remember
@@ -22,7 +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:
   #
@@ -40,95 +43,183 @@ module Liquid
   #                   where 0 is the last item.
   # forloop.first:: Returns true if the item is the first item.
   # forloop.last:: Returns true if the item is the last item.
+  # forloop.parentloop:: Provides access to the parent loop, if present.
   #
   class For < Block
-    Syntax = /(\w+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/   
+    Syntax = /\A(#{VariableSegment}+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
 
-    def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
-        @variable_name = $1
-        @collection_name = $2
-        @name = "#{$1}-#{$2}"           
-        @reversed = $3             
-        @attributes = {}
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = value
-        end        
-      else
-        raise SyntaxError.new("Syntax Error in 'for loop' - Valid syntax: for [item] in [collection]")
-      end
+    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 = new_body
+      @else_block = nil
     end
 
-    def render(context)        
-      context.registers[:for] ||= Hash.new(0)
+    def parse(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
 
-      collection = context[@collection_name]
+    def nodelist
+      @else_block ? [@for_block, @else_block] : [@for_block]
+    end
+
+    def unknown_tag(tag, markup, tokens)
+      return super unless tag == 'else'
+      @else_block = new_body
+    end
+
+    def render_to_output_buffer(context, output)
+      segment = collection_segment(context)
+
+      if segment.empty?
+        render_else(context, output)
+      else
+        render_segment(context, output, segment)
+      end
+
+      output
+    end
+
+    protected
+
+    def lax_parse(markup)
+      if markup =~ Syntax
+        @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, options[:locale].t("errors.syntax.for")
+      end
+    end
+
+    def strict_parse(markup)
+      p = Parser.new(markup)
+      @variable_name = p.consume(:id)
+      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') || p.id?('offset'))
+          raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_attribute")
+        end
+        p.consume
+        set_attribute(attribute, p.expression)
+      end
+      p.consume(:end_of_string)
+    end
+
+    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)
 
-      return '' unless collection.respond_to?(:each) 
-                                                 
-      from = if @attributes['offset'] == 'continue'
-        context.registers[:for][@name].to_i
+      limit_value = context.evaluate(@limit)
+      to = if limit_value.nil?
+        nil
       else
-        context[@attributes['offset']].to_i
+        Utils.to_integer(limit_value) + from
       end
 
-      limit = context[@attributes['limit']]
-      to    = limit ? limit.to_i + from : nil  
-          
-                       
-      segment = slice_collection_using_each(collection, from, to)      
-      
-      return '' if segment.empty?
-      
+      segment = Utils.slice_collection(collection, from, to)
       segment.reverse! if @reversed
 
-      result = []
+      offsets[@name] = from + segment.length
 
-      length = segment.length            
-            
-      # Store our progress through the collection for the continue flag
-      context.registers[:for][@name] = from + segment.length
-              
-      context.stack do 
-        segment.each_with_index do |item, index|     
-          context[@variable_name] = item
-          context['forloop'] = {
-            'name'    => @name,
-            'length'  => length,
-            'index'   => index + 1, 
-            'index0'  => index, 
-            'rindex'  => length - index,
-            'rindex0' => length - index -1,
-            'first'   => (index == 0),
-            'last'    => (index == length - 1) }
-
-          result << render_all(@nodelist, context)
-        end
-      end
-      result     
+      segment
     end
 
-    def slice_collection_using_each(collection, from, to)       
-      segments = []      
-      index = 0      
-      yielded = 0
-      collection.each do |item|         
+    def render_segment(context, output, segment)
+      for_stack = context.registers[:for_stack] ||= []
+      length    = segment.length
 
-        if to && to <= index
-          break
+      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
-        
-        if from <= index                               
-          segments << item
-        end                    
-                
-        index += 1
       end
 
-      segments
+      output
+    end
+
+    def set_attribute(key, expr)
+      case key
+      when 'offset'
+        @from = if expr == 'continue'
+          Usage.increment('for_offset_continue')
+          :continue
+        else
+          parse_expression(expr)
+        end
+      when 'limit'
+        @limit = parse_expression(expr)
+      end
+    end
+
+    def render_else(context, output)
+      if @else_block
+        @else_block.render_to_output_buffer(context, output)
+      else
+        output
+      end
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        (super + [@node.limit, @node.from, @node.collection_name]).compact
+      end
     end
   end
 

lib/liquid/tags/if.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # If is the conditional block
   #
   #   {% if user.admin %}
@@ -10,38 +11,51 @@ module Liquid
   #
   #    There are {% if count < 5 %} less {% else %} more {% endif %} items than you need.
   #
-  #
   class If < Block
-    SyntaxHelp = "Syntax Error in tag 'if' - Valid syntax: if [expression]"
-    Syntax = /(#{QuotedFragment})\s*([=!<>a-z_]+)?\s*(#{QuotedFragment})?/
-    ExpressionsAndOperators = /(?:\b(?:and|or)\b|(?:\s*(?!\b(?:and|or)\b)(?:#{QuotedFragment}|\S+)\s*)+)/
+    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).freeze
 
-    def initialize(tag_name, markup, tokens)    
-    
-      @blocks = []
-      
-      push_block('if', markup)
+    attr_reader :blocks
 
+    def initialize(tag_name, markup, options)
       super
+      @blocks = []
+      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', 'else'].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 render_all(block.attachment, context)            
-          end
+    def render_to_output_buffer(context, output)
+      @blocks.each do |block|
+        if block.evaluate(context)
+          return block.attachment.render_to_output_buffer(context, output)
         end
-        ''
       end
+
+      output
     end
 
     private
@@ -50,30 +64,70 @@ module Liquid
       block = if tag == 'else'
         ElseCondition.new
       else
-        
-        expressions = markup.scan(ExpressionsAndOperators).reverse
-        raise(SyntaxError, SyntaxHelp) unless expressions.shift =~ Syntax 
-
-        condition = Condition.new($1, $2, $3)               
-        
-        while not expressions.empty?
-          operator = expressions.shift 
-          
-          raise(SyntaxError, SyntaxHelp) unless expressions.shift.to_s =~ Syntax    
-          
-          new_condition = Condition.new($1, $2, $3)
-          new_condition.send(operator.to_sym, condition)     
-          condition = new_condition          
-        end                        
-                  
-        condition
+        parse_with_selected_parser(markup)
       end
 
       @blocks.push(block)
-      @nodelist = block.attach(Array.new) 
+      block.attach(new_body)
     end
 
+    def parse_expression(markup)
+      Condition.parse_expression(parse_context, markup)
+    end
 
+    def lax_parse(markup)
+      expressions = markup.scan(ExpressionsAndOperators)
+      raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop =~ Syntax
+
+      condition = Condition.new(parse_expression(Regexp.last_match(1)), Regexp.last_match(2), parse_expression(Regexp.last_match(3)))
+
+      until expressions.empty?
+        operator = expressions.pop.to_s.strip
+
+        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
+
+      condition
+    end
+
+    def strict_parse(markup)
+      p = Parser.new(markup)
+      condition = parse_binary_comparisons(p)
+      p.consume(:end_of_string)
+      condition
+    end
+
+    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 = 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', If)

lib/liquid/tags/ifchanged.rb

@@ -1,18 +1,17 @@
+# 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 = render_all(@nodelist, context)
-        
-        if output != context.registers[:ifchanged]
-          context.registers[:ifchanged] = output
-          output
-        else
-          ''
-        end              
+      if block_output != context.registers[:ifchanged]
+        context.registers[:ifchanged] = block_output
+        output << block_output
       end
+
+      output
     end
   end
 

lib/liquid/tags/include.rb

@@ -1,53 +1,108 @@
+# frozen_string_literal: true
+
 module Liquid
+  # Include allows templates to relate with other templates
+  #
+  # Simply include another template:
+  #
+  #   {% include 'product' %}
+  #
+  # Include a template with a local variable:
+  #
+  #   {% include 'product' with products[0] %}
+  #
+  # Include a template for a collection:
+  #
+  #   {% include 'product' for products %}
+  #
   class Include < Tag
-    Syntax = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?/
+    prepend Tag::Disableable
 
-    def initialize(tag_name, markup, tokens)      
-      if markup =~ Syntax
+    SYNTAX = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
+    Syntax = SYNTAX
 
-        @template_name = $1        
-        @variable_name = $3
-        @attributes    = {}
+    attr_reader :template_name_expr, :variable_name_expr, :attributes
+
+    def initialize(tag_name, markup, options)
+      super
+
+      if markup =~ SYNTAX
+
+        template_name = Regexp.last_match(1)
+        variable_name = Regexp.last_match(3)
+
+        @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] = value
+          @attributes[key] = parse_expression(value)
         end
 
       else
-        raise SyntaxError.new("Error in tag 'include' - Valid syntax: include '[template]' (with|for) [object|collection]")
+        raise SyntaxError, options[:locale].t("errors.syntax.include")
+      end
+    end
+
+    def parse(_tokens)
+    end
+
+    def render_to_output_buffer(context, output)
+      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
+
+      variable = if @variable_name_expr
+        context.evaluate(@variable_name_expr)
+      else
+        context.find_variable(template_name, raise_on_not_found: false)
       end
 
-      super
-    end
-  
-    def parse(tokens)      
-    end
-  
-    def render(context)      
-      file_system = context.registers[:file_system] || Liquid::Template.file_system
-      source  = file_system.read_template_file(context[@template_name])      
-      partial = Liquid::Template.parse(source)      
-      
-      variable = context[@variable_name || @template_name[1..-2]]
-      
-      context.stack do
-        @attributes.each do |key, value|
-          context[key] = context[value]
-        end
-
-        if variable.is_a?(Array)
-          
-          variable.collect do |variable|            
-            context[@template_name[1..-2]] = variable
-            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
 
-        else
-                    
-          context[@template_name[1..-2]] = variable
-          partial.render(context)
-          
+          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
         end
+      ensure
+        context.template_name = old_template_name
+        context.partial       = old_partial
+      end
+
+      output
+    end
+
+    alias_method :parse_context, :options
+    private :parse_context
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.template_name_expr,
+          @node.variable_name_expr,
+        ] + @node.attributes.values
       end
     end
   end

lib/liquid/tags/increment.rb

@@ -0,0 +1,35 @@
+# 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
+  #     multiple instantiations of the template.
+  #     (To achieve the survival, the application must keep the context)
+  #
+  #     if the variable does not exist, it is created with value 0.
+  #
+  #   Hello: {% increment variable %}
+  #
+  # gives you:
+  #
+  #    Hello: 0
+  #    Hello: 1
+  #    Hello: 2
+  #
+  class Increment < Tag
+    def initialize(tag_name, markup, options)
+      super
+      @variable = markup.strip
+    end
+
+    def render_to_output_buffer(context, output)
+      value = context.environments.first[@variable] ||= 0
+      context.environments.first[@variable] = value + 1
+
+      output << value.to_s
+      output
+    end
+  end
+
+  Template.register_tag('increment', Increment)
+end

lib/liquid/tags/inline_comment.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Liquid
+  class InlineComment < Tag
+    def initialize(tag_name, markup, options)
+      super
+      # Semantically, a comment should only ignore everything after it on the line.
+      # Currently, this implementation doesn't support mixing a comment with another tag
+      # but we need to reserve future support for this.
+      if markup.match?(/\n\s*[^#]/)
+        raise SyntaxError, options[:locale].t("errors.syntax.inline_comment_invalid")
+      end
+    end
+
+    def render_to_output_buffer(_context, output)
+      output
+    end
+
+    def blank?
+      true
+    end
+  end
+
+  Template.register_tag('#', InlineComment)
+end

lib/liquid/tags/raw.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Raw < Block
+    Syntax = /\A\s*\z/
+    FullTokenPossiblyInvalid = /\A(.*)#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}\z/om
+
+    def initialize(tag_name, markup, parse_context)
+      super
+
+      ensure_valid_markup(tag_name, markup, parse_context)
+    end
+
+    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
+      [@body]
+    end
+
+    def blank?
+      @body.empty?
+    end
+
+    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', 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

@@ -0,0 +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   = Regexp.last_match(1)
+        @collection_name = parse_expression(Regexp.last_match(2))
+        @attributes      = {}
+        markup.scan(TagAttributes) do |key, value|
+          @attributes[key] = parse_expression(value)
+        end
+      else
+        raise SyntaxError, options[:locale].t("errors.syntax.table_row")
+      end
+    end
+
+    def render_to_output_buffer(context, output)
+      (collection = context.evaluate(@collection_name)) || (return '')
+
+      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
+
+      cols = context.evaluate(@attributes['cols']).to_i
+
+      output << "<tr class=\"row1\">\n"
+      context.stack do
+        tablerowloop = Liquid::TablerowloopDrop.new(length, cols)
+        context['tablerowloop'] = tablerowloop
+
+        collection.each do |item|
+          context[@variable_name] = item
+
+          output << "<td class=\"col#{tablerowloop.col}\">"
+          super
+          output << '</td>'
+
+          if tablerowloop.col_last && !tablerowloop.last
+            output << "</tr>\n<tr class=\"row#{tablerowloop.row + 1}\">"
+          end
+
+          tablerowloop.send(:increment!)
+        end
+      end
+
+      output << "</tr>\n"
+      output
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        super + @node.attributes.values + [@node.collection_name]
+      end
+    end
+  end
+
+  Template.register_tag('tablerow', TableRow)
+end

lib/liquid/tags/unless.rb

@@ -1,33 +1,30 @@
-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.
   #
-  #   {% unless x < 0 %} x is greater than zero {% end %}
+  #   {% 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 )
-        block = @blocks.first
-        unless block.evaluate(context)
-          return render_all(block.attachment, context)            
-        end
-        
-        # After the first condition unless works just like if
-        @blocks[1..-1].each do |block|
-          if block.evaluate(context)            
-            return render_all(block.attachment, context)            
-          end
-        end 
-        
-        ''
+    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', 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.
@@ -15,47 +16,99 @@ module Liquid
   #
   class Template
     attr_accessor :root
-    @@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.key?(tag_name)
+        return @cache[tag_name] if Liquid.cache_classes
+
+        lookup_class(@tags[tag_name]).tap { |o| @cache[tag_name] = o }
+      end
+
+      def []=(tag_name, klass)
+        @tags[tag_name]  = klass.name
+        @cache[tag_name] = klass
+      end
+
+      def delete(tag_name)
+        @tags.delete(tag_name)
+        @cache.delete(tag_name)
+      end
+
+      def each(&block)
+        @tags.each(&block)
+      end
+
+      private
+
+      def lookup_class(name)
+        Object.const_get(name)
+      end
+    end
+
+    attr_reader :profiler
 
     class << self
-      def file_system
-        @@file_system
+      # Sets how strict the parser should be.
+      # :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_accessor :error_mode
+      Template.error_mode = :lax
+
+      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 ||= {}
-      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
 
+      attr_accessor :default_resource_limits
+      Template.default_resource_limits = {}
+      private :default_resource_limits=
+
       # creates a new <tt>Template</tt> object from liquid source code
-      def parse(source)
-        template = Template.new
-        template.parse(source)
-        template
+      # To enable profiling, pass in <tt>profile: true</tt> as an option.
+      # See Liquid::Profiler for more information
+      def parse(source, options = {})
+        new.parse(source, options)
       end
     end
 
-    # creates a new <tt>Template</tt> from an array of tokens. Use <tt>Template.parse</tt> instead
     def initialize
+      @rethrow_errors  = false
+      @resource_limits = ResourceLimits.new(Template.default_resource_limits)
     end
 
     # Parse source code.
     # Returns self for easy chaining
-    def parse(source)
-      @root = Document.new(tokenize(source))
+    def parse(source, options = {})
+      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
 
@@ -80,6 +133,9 @@ module Liquid
     # if you use the same filters over and over again consider registering them globally
     # with <tt>Template.register_filter</tt>
     #
+    # if profiling was enabled in <tt>Template#parse</tt> then the resulting profiling information
+    # will be available via <tt>Template#profiler</tt>
+    #
     # Following options can be passed:
     #
     #  * <tt>filters</tt> : array with local filters
@@ -91,59 +147,89 @@ module Liquid
 
       context = case args.first
       when Liquid::Context
-        args.shift
+        c = args.shift
+
+        if @rethrow_errors
+          c.exception_renderer = Liquid::RAISE_EXCEPTION_LAMBDA
+        end
+
+        c
+      when Liquid::Drop
+        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)
+        Context.new([args.shift, assigns], instance_assigns, registers, @rethrow_errors, @resource_limits)
       when nil
-        Context.new(assigns, instance_assigns, registers, @rethrow_errors)
+        Context.new(assigns, instance_assigns, registers, @rethrow_errors, @resource_limits)
       else
-        raise ArgumentError, "Expect Hash or Liquid::Context as parameter"
+        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
+        apply_options_to_context(context, options)
+      when Module, Array
+        context.add_filters(args.pop)
+      end
 
-      when Module
-        context.add_filters(args.pop)
-      when Array
-        context.add_filters(args.pop)
+      # 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 a array back here. join will make a string out of it
-        @root.render(context).join
+        @root.render_to_output_buffer(context, output || +'')
+      rescue Liquid::MemoryError => e
+        context.handle_error(e)
       ensure
         @errors = context.errors
       end
     end
 
     def render!(*args)
-      @rethrow_errors = true; render(*args)
+      @rethrow_errors = true
+      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 = source.split(TemplateParser)
+    def configure_options(options)
+      if (profiling = options[:profile])
+        raise "Profiler not loaded, require 'liquid/profiler' first" unless defined?(Liquid::Profiler)
+      end
 
-      # removes the rogue empty element at the beginning of the array
-      tokens.shift if tokens[0] and tokens[0].empty?
-
-      tokens
+      @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/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

@@ -0,0 +1,85 @@
+# 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)
+        collection.load_slice(from, to)
+      else
+        slice_collection_using_each(collection, from, to)
+      end
+    end
+
+    def self.slice_collection_using_each(collection, from, to)
+      segments = []
+      index    = 0
+
+      # Maintains Ruby 1.8.7 String#each behaviour on 1.9
+      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
+
+        if from <= index
+          segments << item
+        end
+
+        index += 1
+      end
+
+      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
   #
@@ -11,39 +12,141 @@ module Liquid
   #   {{ user | link }}
   #
   class Variable
-    FilterParser = /(?:#{FilterSeparator}|(?:\s*(?!(?:#{FilterSeparator}))(?:#{QuotedFragment}|\S+)\s*)+)/
-    attr_accessor :filters, :name
+    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
 
-    def initialize(markup)
-      @markup  = markup
-      @name    = nil
+    attr_accessor :filters, :name, :line_number
+    attr_reader :parse_context
+    alias_method :options, :parse_context
+
+    include ParserSwitching
+
+    def initialize(markup, parse_context)
+      @markup        = markup
+      @name          = nil
+      @parse_context = parse_context
+      @line_number   = parse_context.line_number
+
+      strict_parse_with_error_mode_fallback(markup)
+    end
+
+    def raw
+      @markup
+    end
+
+    def markup_context(markup)
+      "in \"{{#{markup}}}\""
+    end
+
+    def lax_parse(markup)
       @filters = []
-      if match = markup.match(/\s*(#{QuotedFragment})(.*)/)
-        @name = match[1]
-        if match[2].match(/#{FilterSeparator}\s*(.*)/)
-          filters = Regexp.last_match(1).scan(FilterParser)
-          filters.each do |f|
-            if matches = f.match(/\s*(\w+)/)
-              filtername = matches[1]
-              filterargs = f.scan(/(?:#{FilterArgumentSeparator}|#{ArgumentSeparator})\s*(#{QuotedFragment})/).flatten
-              @filters << [filtername.to_sym, 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
 
+    def strict_parse(markup)
+      @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)
+        filterargs = p.consume?(:colon) ? parse_filterargs(p) : []
+        @filters << parse_filter_expressions(filtername, filterargs)
+      end
+      p.consume(:end_of_string)
+    end
+
+    def parse_filterargs(p)
+      # first argument
+      filterargs = [p.argument]
+      # followed by comma separated others
+      filterargs << p.argument while p.consume?(:comma)
+      filterargs
+    end
+
     def render(context)
-      return '' if @name.nil?
-      @filters.inject(context[@name]) do |output, filter|
-        filterargs = filter[1].to_a.collect do |a|
-         context[a]
+      obj = context.evaluate(@name)
+
+      @filters.each do |filter_name, filter_args, filter_kwargs|
+        filter_args = evaluate_filter_expressions(context, filter_args, filter_kwargs)
+        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 = nil
+      unparsed_args.each do |a|
+        if (matches = a.match(JustTagAttributes))
+          keyword_args           ||= {}
+          keyword_args[matches[1]] = Expression.parse(matches[2])
+        else
+          filter_args << Expression.parse(a)
         end
-        begin
-          output = context.invoke(filter[0], output, *filterargs)
-        rescue FilterNotFound
-          raise FilterNotFound, "Error - filter '#{filter[0]}' in '#{@markup.strip}' could not be found."
+      end
+      result = [filter_name, filter_args]
+      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) }
+      if filter_kwargs
+        parsed_kwargs = {}
+        filter_kwargs.each do |key, expr|
+          parsed_kwargs[key] = context.evaluate(expr)
         end
+        parsed_args << parsed_kwargs
+      end
+      parsed_args
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [@node.name] + @node.filters.flatten
       end
     end
   end

lib/liquid/variable_lookup.rb

@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+
+module Liquid
+  class VariableLookup
+    SQUARE_BRACKETED = /\A\[(.*)\]\z/m
+    COMMAND_METHODS  = ['size', 'first', 'last'].freeze
+
+    attr_reader :name, :lookups
+
+    def self.parse(markup)
+      new(markup)
+    end
+
+    def initialize(markup)
+      lookups = markup.scan(VariableParser)
+
+      name = lookups.shift
+      if name =~ SQUARE_BRACKETED
+        name = Expression.parse(Regexp.last_match(1))
+      end
+      @name = name
+
+      @lookups       = lookups
+      @command_flags = 0
+
+      @lookups.each_index do |i|
+        lookup = lookups[i]
+        if lookup =~ SQUARE_BRACKETED
+          lookups[i] = Expression.parse(Regexp.last_match(1))
+        elsif COMMAND_METHODS.include?(lookup)
+          @command_flags |= 1 << i
+        end
+      end
+    end
+
+    def evaluate(context)
+      name   = context.evaluate(@name)
+      object = context.find_variable(name)
+
+      @lookups.each_index do |i|
+        key = context.evaluate(@lookups[i])
+
+        # 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?(: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)
+          object = res.to_liquid
+
+          # Some special cases. If the part wasn't in square brackets and
+          # no key with the same name was found we interpret following calls
+          # as commands and call them on the current object
+        elsif @command_flags & (1 << i) != 0 && object.respond_to?(key)
+          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 or
+          # raise an exception if `strict_variables` option is set to true
+        else
+          return nil unless context.strict_variables
+          raise Liquid::UndefinedVariable, "undefined variable #{key}"
+        end
+
+        # If we are dealing with a drop here we have to
+        object.context = context if object.respond_to?(:context=)
+      end
+
+      object
+    end
+
+    def ==(other)
+      self.class == other.class && state == other.state
+    end
+
+    protected
+
+    def state
+      [@name, @lookups, @command_flags]
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        @node.lookups
+      end
+    end
+  end
+end

lib/liquid/version.rb

@@ -0,0 +1,6 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+module Liquid
+  VERSION = "5.0.0"
+end

liquid.gemspec

@@ -1,28 +1,34 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+lib = File.expand_path('../lib/', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+require "liquid/version"
+
 Gem::Specification.new do |s|
-  s.name = %q{liquid}
-  s.version = "2.1.3"
+  s.name        = "liquid"
+  s.version     = Liquid::VERSION
+  s.platform    = Gem::Platform::RUBY
+  s.summary     = "A secure, non-evaling end user template engine with aesthetic markup."
+  s.authors     = ["Tobias Lütke"]
+  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.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version=
-  s.authors = ["Tobias Luetke"]
-  s.description = %q{A secure, non-evaling end user template engine with aesthetic markup.}
-  s.email = %q{tobi@leetsoft.com}
-  s.extra_rdoc_files = ["History.txt", "Manifest.txt", "README.txt"]
-  s.files = ["CHANGELOG", "History.txt", "MIT-LICENSE", "Manifest.txt", "README.txt", "Rakefile", "lib/extras/liquid_view.rb", "lib/liquid.rb", "lib/liquid/block.rb", "lib/liquid/condition.rb", "lib/liquid/context.rb", "lib/liquid/document.rb", "lib/liquid/drop.rb", "lib/liquid/errors.rb", "lib/liquid/extensions.rb", "lib/liquid/file_system.rb", "lib/liquid/htmltags.rb", "lib/liquid/module_ex.rb", "lib/liquid/standardfilters.rb", "lib/liquid/strainer.rb", "lib/liquid/tag.rb", "lib/liquid/tags/assign.rb", "lib/liquid/tags/capture.rb", "lib/liquid/tags/case.rb", "lib/liquid/tags/comment.rb", "lib/liquid/tags/cycle.rb", "lib/liquid/tags/for.rb", "lib/liquid/tags/if.rb", "lib/liquid/tags/ifchanged.rb", "lib/liquid/tags/include.rb", "lib/liquid/tags/unless.rb", "lib/liquid/template.rb", "lib/liquid/variable.rb"]
-  s.has_rdoc = true
-  s.homepage = %q{http://www.liquidmarkup.org}
-  s.rdoc_options = ["--main", "README.txt"]
-  s.require_paths = ["lib"]
-  s.rubyforge_project = %q{liquid}
-  s.rubygems_version = %q{1.3.1}
-  s.summary = %q{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"
 
-  if s.respond_to? :specification_version then
-    current_version = Gem::Specification::CURRENT_SPECIFICATION_VERSION
-    s.specification_version = 2
+  s.metadata['allowed_push_host'] = 'https://rubygems.org'
 
-    if Gem::Version.new(Gem::RubyGemsVersion) >= Gem::Version.new('1.2.0') then
-    else
-    end
-  else
-  end
+  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', '~> 13.0')
+  s.add_development_dependency('minitest')
 end

performance/benchmark.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require 'benchmark/ips'
+require_relative 'theme_runner'
+
+Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
+profiler = ThemeRunner.new
+
+Benchmark.ips do |x|
+  x.time   = 10
+  x.warmup = 5
+
+  puts
+  puts "Running benchmark for #{x.time} seconds (with #{x.warmup} seconds warmup)."
+  puts
+
+  x.report("parse:") { profiler.compile }
+  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

@@ -0,0 +1,26 @@
+# 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} mode..."
+  results = StackProf.run(mode: profile_type) do
+    200.times do
+      profiler.run
+    end
+  end
+
+  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
+  end
+
+  StackProf::Report.new(results).print_text(false, 20)
+  File.write(ENV['FILENAME'] + "." + profile_type.to_s, Marshal.dump(results)) if ENV['FILENAME']
+end

performance/shopify.rb

@@ -1,92 +0,0 @@
-# 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. 
-# All this is to make the benchmark as non syntetic as possible. All templates and tests are lifted from
-# direct real-world usage and the profiler measures code that looks very similar to the way it looks in 
-# 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 'rubygems'
-require 'active_support'
-require 'yaml'
-require 'digest/md5'
-require File.dirname(__FILE__) + '/shopify/liquid'
-require File.dirname(__FILE__) + '/shopify/database.rb'
-
-require "ruby-prof" rescue fail("install ruby-prof extension/gem")
-
-class ThemeProfiler
-  
-  # 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|
-      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]
-    end.compact
-  end  
-  
-  
-  def profile
-    RubyProf.measure_mode = RubyProf::WALL_TIME
-    
-    # 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
-      html = nil
-      page_template = File.basename(template_name, File.extname(template_name))
-      
-      # Profile compiling and rendering both
-      RubyProf.resume { html = compile_and_render(liquid, layout, assigns, page_template) }
-      
-      # return the result and the MD5 of the content, this can be used to detect regressions between liquid version
-      $stdout.puts "* rendered template %s, content: %s" % [template_name, Digest::MD5.hexdigest(html)]
-      
-      # Uncomment to dump html files to /tmp so that you can inspect for errors
-      # File.open("/tmp/#{File.basename(template_name)}.html", "w+") { |fp| fp <<html}
-    end
-  
-    RubyProf.stop    
-  end
-  
-  def compile_and_render(template, layout, assigns, page_template)    
-    tmpl = Liquid::Template.new
-    tmpl.assigns['page_title'] = 'Page title'
-    tmpl.assigns['template'] = page_template
-    
-    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    
-  end
-end
-
-
-  profiler = ThemeProfiler.new
-
-  puts 'Running profiler...'
-
-  results  = profiler.profile
-  
-  puts 'Success'
-  puts
-
-[RubyProf::FlatPrinter, RubyProf::GraphPrinter, RubyProf::GraphHtmlPrinter, RubyProf::CallTreePrinter].each do |klass|
-  filename = (ENV['TMP'] || '/tmp') + (klass.name.include?('Html') ? "/liquid.#{klass.name.downcase}.html" : "/liquid.#{klass.name.downcase}.txt")
-  filename.gsub!(/:+/, '_')
-  File.open(filename, "w+") { |fp| klass.new(results).print(fp) }
-  $stderr.puts "wrote #{klass.name} output to #{filename}"
-end
-
-
-

performance/shopify/comment_form.rb

@@ -1,18 +1,20 @@
+# frozen_string_literal: true
+
 class CommentForm < Liquid::Block
   Syntax = /(#{Liquid::VariableSignature}+)/
 
-  def initialize(tag_name, markup, tokens)
-    if markup =~ Syntax
-      @variable_name = $1
-      @attributes = {}
-    else
-      raise SyntaxError.new("Syntax Error in 'comment_form' - Valid syntax: comment_form [article]")
-    end
-    
+  def initialize(tag_name, markup, options)
     super
+
+    if markup =~ Syntax
+      @variable_name = Regexp.last_match(1)
+      @attributes    = {}
+    else
+      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

@@ -1,11 +1,13 @@
-require 'yaml'
-module Database
+# frozen_string_literal: true
 
+require 'yaml'
+
+module Database
   # Load the standard vision toolkit database and re-arrage it to be simply exportable
   # 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

@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
+require 'json'
+
 module JsonFilter
-  
   def json(object)
-    object.reject {|k,v| k == "collections" }.to_json
+    JSON.dump(object.reject { |k, _v| k == "collections" })
   end
-  
 end

performance/shopify/liquid.rb

@@ -1,18 +1,21 @@
-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 @@
-class Paginate < Liquid::Block
-  Syntax     = /(#{Liquid::QuotedFragment})\s*(by\s*(\d+))?/
+# frozen_string_literal: true
 
-  def initialize(tag_name, markup, tokens)
-    @nodelist = []
+class Paginate < Liquid::Block
+  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
@@ -17,50 +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
-  
-    super
   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
@@ -73,18 +72,18 @@ class Paginate < Liquid::Block
         end
       end
 
-      render_all(@nodelist, context)      
+      super
     end
   end
 
   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