Merge branch 'master' into fix-constants

* Add ForceEqualSignAlignment to .rubocop.yml

* Revert ForceEqualSignAlignment cop

* Update method alignment

* Undo addition of whitespace to improve readability

* Fix missing alignment

.github/probots.yml

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

.gitignore

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

.rubocop.yml

@@ -0,0 +1,17 @@
+inherit_from:
+  - 'https://shopify.github.io/ruby-style-guide/rubocop.yml'
+  - .rubocop_todo.yml
+
+require: rubocop-performance
+
+Performance:
+  Enabled: true
+
+AllCops:
+  TargetRubyVersion: 2.4
+  Exclude:
+    - 'vendor/bundle/**/*'
+
+Naming/MethodName:
+  Exclude:
+    - 'example/server/liquid_servlet.rb'

.rubocop_todo.yml

@@ -0,0 +1,29 @@
+# This configuration was generated by
+# `rubocop --auto-gen-config`
+# on 2019-09-11 06:34:25 +1000 using RuboCop version 0.74.0.
+# 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: 98
+# Cop supports --auto-correct.
+# Configuration parameters: AutoCorrect, AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
+# URISchemes: http, https
+Metrics/LineLength:
+  Max: 294
+
+# Offense count: 5
+Style/ClassVars:
+  Exclude:
+    - 'lib/liquid/condition.rb'
+    - 'lib/liquid/strainer.rb'
+    - 'lib/liquid/template.rb'

.travis.yml

@@ -1,13 +1,26 @@
-rvm:
-  - 1.8.7
-  - 1.9.3
-  - ree
-  - jruby-18mode
-  - jruby-19mode
-  - rbx-18mode
-  - rbx-19mode
+language: ruby
+cache: bundler
 
-script: "rake test"
+rvm:
+  - 2.4
+  - 2.5
+  - &latest_ruby 2.6
+  - 2.7
+  - ruby-head
+
+matrix:
+  include:
+    - rvm: *latest_ruby
+      script: bundle exec rake memory_profile:run
+      name: Profiling Memory Usage
+  allow_failures:
+    - rvm: ruby-head
+
+branches:
+  only:
+    - master
+    - gh-pages
+    - /.*-stable/
 
 notifications:
   disable: true

CONTRIBUTING.md

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

Gemfile

@@ -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', '~> 0.74.0', require: false
+  gem 'rubocop-performance', require: false
+
+  platform :mri, :truffleruby do
+    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'master'
+  end
+end

History.md

@@ -1,29 +1,216 @@
-# Liquid Version History
+# Liquid Change Log
+
+## 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.
 
-## 2.6.0 / Master branch (not yet released)
-
-* ...
 * Bugfix for #106: fix example servlet [gnowoel]
-* Bugfix for #97: strip_html filter supports multi-line tags [Jo Liss, joliss]
-* Bugfix for #114: strip_html filter supports style tags [James Allardice, jamesallardice]
-* Bugfix for #117: 'now' support for date filter in Ruby 1.9 [Notre Dame Webgroup, ndwebgroup]
-* Bugfix for #166: truncate filter on UTF-8 strings with Ruby 1.8 [Florian Weingarten, fw42]
-* Bugfix for #204: 'raw' parsing bug [Florian Weingarten, fw42]
-* Bugfix for #150: 'for' parsing bug [Peter Schröder, phoet]
-* Bugfix for #126: Strip CRLF in strip_newline [Peter Schröder, phoet]
-* Allow a Liquid::Drop to be passed into Template#render [Daniel Huckstep, darkhelmet]
-* Resource limits [Florian Weingarten, fw42]
-* Add reverse filter [Jay Strybis, unreal]
+* Bugfix for #97: strip_html filter supports multi-line tags [Jo Liss]
+* Bugfix for #114: strip_html filter supports style tags [James Allardice]
+* Bugfix for #117: 'now' support for date filter in Ruby 1.9 [Notre Dame Webgroup]
+* Bugfix for #166: truncate filter on UTF-8 strings with Ruby 1.8 [Florian Weingarten]
+* Bugfix for #204: 'raw' parsing bug [Florian Weingarten]
+* Bugfix for #150: 'for' parsing bug [Peter Schröder]
+* Bugfix for #126: Strip CRLF in strip_newline [Peter Schröder]
+* Bugfix for #174, "can't convert Fixnum into String" for "replace" [jsw0528]
+* Allow a Liquid::Drop to be passed into Template#render [Daniel Huckstep]
+* Resource limits [Florian Weingarten]
+* Add reverse filter [Jay Strybis]
 * Add utf-8 support
-* Use array instead of Hash to keep the registered filters [Tasos Stathopoulos, astathopoulos]
-* Cache tokenized partial templates [Tom Burns, boourns]
-* Avoid warnings in Ruby 1.9.3 [Marcus Stollsteimer, stomar]
-* Better documentation for 'include' tag (closes #163) [Peter Schröder, phoet]
-* Use of BigDecimal on filters to have better precision (closes #155) [Arthur Nogueira Neves, arthurnn]
+* Use array instead of Hash to keep the registered filters [Tasos Stathopoulos]
+* Cache tokenized partial templates [Tom Burns]
+* Avoid warnings in Ruby 1.9.3 [Marcus Stollsteimer]
+* Better documentation for 'include' tag (closes #163) [Peter Schröder]
+* Use of BigDecimal on filters to have better precision (closes #155) [Arthur Nogueira Neves]
 
+## 2.5.5 / 2014-01-10 / branch "2-5-stable"
+
+Security fix, cherry-picked from master (4e14a65):
+* Don't call to_sym when creating conditions for security reasons (#273) [Bouke van der Bijl]
+* 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
 

README.md

@@ -1,9 +1,12 @@
+[![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 from Shopify](http://wiki.shopify.com/Liquid)
+* [Liquid Wiki at GitHub](https://github.com/Shopify/liquid/wiki)
 * [Website](http://liquidmarkup.org/)
 
 ## Introduction
@@ -39,6 +42,8 @@ Liquid is a template engine which was written with very specific requirements:
 
 ## How to use Liquid
 
+Install Liquid by adding `gem 'liquid'` to your gemfile.
+
 Liquid supports a very simple API based around the Liquid::Template class.
 For standard use you can just pass it the content of a file and call render with a parameters hash.
 
@@ -47,4 +52,63 @@ For standard use you can just pass it the content of a file and call render with
 @template.render('name' => 'tobi')                # => "hi tobi"
 ```
 
-[![Build Status](https://secure.travis-ci.org/Shopify/liquid.png)](http://travis-ci.org/Shopify/liquid)
+### 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.

Rakefile

@@ -1,53 +1,106 @@
-#!/usr/bin/env ruby
+# frozen_string_literal: true
 
-require 'rubygems'
 require 'rake'
 require 'rake/testtask'
-require 'rubygems/package_task'
+$LOAD_PATH.unshift(File.expand_path("../lib", __FILE__))
+require "liquid/version"
 
-task :default => 'test'
+task(default: [:test, :rubocop])
 
-Rake::TestTask.new(:test) do |t|
+desc('run test suite with default parser')
+Rake::TestTask.new(:base_test) do |t|
   t.libs << '.' << 'lib' << 'test'
-  t.test_files = FileList['test/liquid/**/*_test.rb']
-  t.verbose = false
+  t.test_files = FileList['test/{integration,unit}/**/*_test.rb']
+  t.verbose    = false
 end
 
-gemspec = eval(File.read('liquid.gemspec'))
-Gem::PackageTask.new(gemspec) do |pkg|
-  pkg.gem_spec = gemspec
+desc('run test suite with warn error mode')
+task :warn_test do
+  ENV['LIQUID_PARSER_MODE'] = 'warn'
+  Rake::Task['base_test'].invoke
 end
 
-desc "Build the gem and release it to rubygems.org"
-task :release => :gem do
-  sh "gem push pkg/liquid-#{gemspec.version}.gem"
+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['base_test'].reenable
+    Rake::Task['base_test'].invoke
+
+    ENV['LIQUID_PARSER_MODE'] = 'strict'
+    Rake::Task['base_test'].reenable
+    Rake::Task['base_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"
+  desc "Run the liquid benchmark with lax parsing"
   task :run do
-    ruby "./performance/benchmark.rb"
+    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
-
   desc "Run the liquid profile/performance coverage"
   task :run do
     ruby "./performance/profile.rb"
   end
 
-  desc "Run KCacheGrind"
-  task :grind => :run  do
-    system "qcachegrind /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
 
-desc "Run example"
+namespace :memory_profile do
+  desc "Run memory profiler"
+  task :run do
+    ruby "./performance/memory_profile.rb"
+  end
+end
+
+desc("Run example")
 task :example do
   ruby "-w -d -Ilib example/server/server.rb"
 end
+
+task :console do
+  exec 'irb -I lib -r liquid'
+end

example/server/example_servlet.rb

@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 module ProductsFilter
   def price(integer)
-    sprintf("$%.2d USD", integer / 100.0)
+    format("$%.2d USD", integer / 100.0)
   end
 
   def prettyprint(text)
-    text.gsub( /\*(.*)\*/, '<b>\1</b>' )
+    text.gsub(/\*(.*)\*/, '<b>\1</b>')
   end
 
   def count(array)
@@ -17,25 +19,28 @@ module ProductsFilter
 end
 
 class Servlet < LiquidServlet
-
   def index
     { 'date' => Time.now }
   end
 
   def products
-    { 'products' => products_list, 'description' => description, 'section' => 'Snowboards', 'cool_products' => true}
+    { 'products' => products_list, 'more_products' => more_products_list, 'description' => description, 'section' => 'Snowboards', 'cool_products' => true }
   end
 
   private
 
   def products_list
-    [{'name' => 'Arbor Draft', 'price' => 39900, 'description' => 'the *arbor draft* is a excellent product' },
-    {'name' => 'Arbor Element', 'price' => 40000, 'description' => 'the *arbor element* rocks for freestyling'},
-    {'name' => 'Arbor Diamond', 'price' => 59900, 'description' => 'the *arbor diamond* is a made up product because im obsessed with arbor and have no creativity'}]
+    [{ 'name' => 'Arbor Draft', 'price' => 39900, 'description' => 'the *arbor draft* is a excellent product' },
+     { 'name' => 'Arbor Element', 'price' => 40000, 'description' => 'the *arbor element* rocks for freestyling' },
+     { 'name' => 'Arbor Diamond', 'price' => 59900, 'description' => 'the *arbor diamond* is a made up product because im obsessed with arbor and have no creativity' }]
+  end
+
+  def more_products_list
+    [{ 'name' => 'Arbor Catalyst', 'price' => 39900, 'description' => 'the *arbor catalyst* is an advanced drop-through for freestyle and flatground performance and versatility' },
+     { 'name' => 'Arbor Fish', 'price' => 40000, 'description' => 'the *arbor fish* is a compact pin that features an extended wheelbase and time-honored teardrop shape' }]
   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

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

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

@@ -16,12 +16,12 @@
   </head>
 
   <body>
-
+    {% assign all_products = products | concat: more_products  %}
     <h1>{{ description | split: '~' | first }}</h1>
 
     <h2>{{ description | split: '~' | last }}</h2>
 
-    <h2>There are currently {{products | count}} products in the {{section}} catalog</h2>
+    <h2>There are currently {{all_products | count}} products in the {{section}} catalog</h2>
 
     {% if cool_products %}
       Cool products :)
@@ -31,7 +31,7 @@
 
     <ul id="products">
 
-      {% for product in products %}
+      {% for product in all_products %}
         <li>
           <h2>{{product.name}}</h2>
           Only {{product.price | price }}

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
@@ -20,50 +22,68 @@
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 module Liquid
-  FilterSeparator             = /\|/
-  ArgumentSeparator           = ','
-  FilterArgumentSeparator     = ':'
-  VariableAttributeSeparator  = '.'
-  TagStart                    = /\{\%/
-  TagEnd                      = /\%\}/
-  VariableSignature           = /\(?[\w\-\.\[\]]\)?/
-  VariableSegment             = /[\w\-]/
-  VariableStart               = /\{\{/
-  VariableEnd                 = /\}\}/
-  VariableIncompleteEnd       = /\}\}?/
-  QuotedString                = /"[^"]*"|'[^']*'/
-  QuotedFragment              = /#{QuotedString}|(?:[^\s,\|'"]|#{QuotedString})+/o
-  StrictQuotedFragment        = /"[^"]+"|'[^']+'|[^\s|:,]+/
-  FirstFilterArgument         = /#{FilterArgumentSeparator}(?:#{StrictQuotedFragment})/o
-  OtherFilterArgument         = /#{ArgumentSeparator}(?:#{StrictQuotedFragment})/o
-  SpacelessFilter             = /^(?:'[^']+'|"[^"]+"|[^'"])*#{FilterSeparator}(?:#{StrictQuotedFragment})(?:#{FirstFilterArgument}(?:#{OtherFilterArgument})*)?/o
-  Expression                  = /(?:#{QuotedFragment}(?:#{SpacelessFilter})*)/o
-  TagAttributes               = /(\w+)\s*\:\s*(#{QuotedFragment})/o
-  AnyStartingTag              = /\{\{|\{\%/
-  PartialTemplateParser       = /#{TagStart}.*?#{TagEnd}|#{VariableStart}.*?#{VariableIncompleteEnd}/o
-  TemplateParser              = /(#{PartialTemplateParser}|#{AnyStartingTag})/o
-  VariableParser              = /\[[^\]]+\]|#{VariableSegment}+\??/o
+  FILTER_SEPARATOR             = /\|/
+  ARGUMENT_SEPARATOR           = ','
+  FILTER_ARGUMENT_SEPARATOR    = ':'
+  VARIABLE_ATTRIBUTE_SEPARATOR = '.'
+  WHITESPACE_CONTROL           = '-'
+  TAG_START                    = /\{\%/
+  TAG_END                      = /\%\}/
+  VARIABLE_SIGNATURE           = /\(?[\w\-\.\[\]]\)?/
+  VARIABLE_SEGMENT             = /[\w\-]/
+  VARIABLE_START               = /\{\{/
+  VARIABLE_END                 = /\}\}/
+  VARIABLE_INCOMPLETE_END      = /\}\}?/
+  QUOTED_STRING                = /"[^"]*"|'[^']*'/
+  QUOTED_FRAGMENT              = /#{QUOTED_STRING}|(?:[^\s,\|'"]|#{QUOTED_STRING})+/o
+  TAG_ATTRIBUTES               = /(\w+)\s*\:\s*(#{QUOTED_FRAGMENT})/o
+  ANY_STARTING_TAG             = /#{TAG_START}|#{VARIABLE_START}/o
+  PARTIAL_TEMPLATE_PARSER      = /#{TAG_START}.*?#{TAG_END}|#{VARIABLE_START}.*?#{VARIABLE_INCOMPLETE_END}/om
+  TEMPLATE_PARSER              = /(#{PARTIAL_TEMPLATE_PARSER}|#{ANY_STARTING_TAG})/om
+  VARIABLE_PARSER              = /\[[^\]]+\]|#{VARIABLE_SEGMENT}+\??/o
+
+  singleton_class.send(:attr_accessor, :cache_classes)
+  self.cache_classes = true
 end
 
 require "liquid/version"
+require 'liquid/parse_tree_visitor'
+require 'liquid/lexer'
+require 'liquid/parser'
+require 'liquid/i18n'
 require 'liquid/drop'
+require 'liquid/tablerowloop_drop'
+require 'liquid/forloop_drop'
 require 'liquid/extensions'
 require 'liquid/errors'
 require 'liquid/interrupts'
 require 'liquid/strainer'
+require 'liquid/expression'
 require 'liquid/context'
+require 'liquid/parser_switching'
 require 'liquid/tag'
 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'
 
 # 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 }
+Dir["#{__dir__}/liquid/registers/*.rb"].each { |f| require f }
+
+require 'liquid/legacy'

lib/liquid/block.rb

@@ -1,126 +1,80 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   class Block < Tag
-    IsTag             = /^#{TagStart}/o
-    IsVariable        = /^#{VariableStart}/o
-    FullToken         = /^#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}$/o
-    ContentOfVariable = /^#{VariableStart}(.*)#{VariableEnd}$/o
+    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 delimiter 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 = BlockBody.new
+      while parse_body(@body, tokens)
       end
-
-      # Make sure that it's ok to end parsing in the current block.
-      # Effectively this method will throw an exception unless the current block is
-      # of type Document
-      assert_missing_delimitation!
     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, _params, _tokens)
+      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}"
-    end
-
     def block_name
       @tag_name
     end
 
-    def create_variable(token)
-      token.scan(ContentOfVariable) do |content|
-        return Variable.new(content.first)
-      end
-      raise SyntaxError.new("Variable '#{token}' was not properly terminated with regexp: #{VariableEnd.inspect} ")
-    end
-
-    def render(context)
-      render_all(@nodelist, context)
+    def block_delimiter
+      @block_delimiter ||= "end#{block_name}"
     end
 
     protected
 
-    def assert_missing_delimitation!
-      raise SyntaxError.new("#{block_name} tag was never closed")
-    end
+    def parse_body(body, tokens)
+      if parse_context.depth >= MAX_DEPTH
+        raise StackLevelError, "Nesting too deep"
+      end
+      parse_context.depth += 1
+      begin
+        body.parse(tokens, parse_context) do |end_tag_name, end_tag_params|
+          @blank &&= body.blank?
 
-    def render_all(list, context)
-      output = []
-      context.resource_limits[:render_length_current] = 0
-      context.resource_limits[:render_score_current] += list.length
-
-      list.each do |token|
-        # Break out if we have any unhanded interrupts.
-        break if context.has_interrupt?
-
-        begin
-          # If we get an Interrupt that means the block must stop processing. An
-          # Interrupt is any command that stops block execution such as {% break %}
-          # or {% continue %}
-          if token.is_a? Continue or token.is_a? Break
-            context.push_interrupt(token.interrupt)
-            break
+          return false if end_tag_name == block_delimiter
+          unless end_tag_name
+            raise SyntaxError, parse_context.locale.t("errors.syntax.tag_never_closed", block_name: block_name)
           end
 
-          token_output = (token.respond_to?(:render) ? token.render(context) : token)
-          context.resource_limits[:render_length_current] += (token_output.respond_to?(:length) ? token_output.length : 1)
-          if context.resource_limits_reached?
-            context.resource_limits[:reached] = true
-            raise MemoryError.new("Memory limits exceeded")
-          end
-          output << token_output
-        rescue MemoryError => e
-          raise e
-        rescue ::StandardError => e
-          output << (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
 
-      output.join
+      true
     end
   end
 end

lib/liquid/block_body.rb

@@ -0,0 +1,202 @@
+# frozen_string_literal: true
+
+module Liquid
+  class BlockBody
+    LIQUID_TAG_TOKEN      = /\A\s*(\w+)\s*(.*?)\z/o
+    FULL_TOKEN            = /\A#{TAG_START}#{WHITESPACE_CONTROL}?(\s*)(\w+)(\s*)(.*?)#{WHITESPACE_CONTROL}?#{TAG_END}\z/om
+    CONTENT_OF_VARIABLE   = /\A#{VARIABLE_START}#{WHITESPACE_CONTROL}?(.*?)#{WHITESPACE_CONTROL}?#{VARIABLE_END}\z/om
+    WHITESPACE_OR_NOTHING = /\A\s*\z/
+    TAG_START_STRING      = "{%"
+    VAR_START_STRING      = "{{"
+
+    attr_reader :nodelist
+
+    def initialize
+      @nodelist = []
+      @blank    = true
+    end
+
+    def parse(tokenizer, parse_context, &block)
+      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
+
+    private def parse_for_liquid_tag(tokenizer, parse_context)
+      while (token = tokenizer.shift)
+        unless token.empty? || token =~ WHITESPACE_OR_NOTHING
+          unless token =~ LIQUID_TAG_TOKEN
+            # 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
+
+    private def parse_for_document(tokenizer, parse_context, &block)
+      while (token = tokenizer.shift)
+        next if token.empty?
+        case
+        when token.start_with?(TAG_START_STRING)
+          whitespace_handler(token, parse_context)
+          unless token =~ FULL_TOKEN
+            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'
+            liquid_tag_tokenizer = Tokenizer.new(markup, line_number: parse_context.line_number, for_liquid_tag: true)
+            next parse_for_liquid_tag(liquid_tag_tokenizer, parse_context, &block)
+          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?(VAR_START_STRING)
+          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 =~ WHITESPACE_OR_NOTHING)
+        end
+        parse_context.line_number = tokenizer.line_number
+      end
+
+      yield nil, nil
+    end
+
+    def whitespace_handler(token, parse_context)
+      if token[2] == WHITESPACE_CONTROL
+        previous_token = @nodelist.last
+        if previous_token.is_a?(String)
+          previous_token.rstrip!
+        end
+      end
+      parse_context.trim_whitespace = (token[-3] == WHITESPACE_CONTROL)
+    end
+
+    def blank?
+      @blank
+    end
+
+    def render(context)
+      render_to_output_buffer(context, +'')
+    end
+
+    def render_to_output_buffer(context, output)
+      context.resource_limits.render_score += @nodelist.length
+
+      idx = 0
+      while (node = @nodelist[idx])
+        previous_output_size = output.bytesize
+
+        case node
+        when String
+          output << node
+        when Variable
+          render_node(context, output, node)
+        when Block
+          render_node(context, node.blank? ? +'' : output, node)
+          break if context.interrupt? # might have happened in a for-block
+        when Continue, Break
+          # 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 %}
+          context.push_interrupt(node.interrupt)
+          break
+        else # Other non-Block tags
+          render_node(context, output, node)
+          break if context.interrupt? # might have happened through an include
+        end
+        idx += 1
+
+        raise_if_resource_limits_reached(context, output.bytesize - previous_output_size)
+      end
+
+      output
+    end
+
+    private
+
+    def render_node(context, output, node)
+      if node.disabled?(context)
+        output << node.disabled_error_message
+        return
+      end
+      disable_tags(context, node.disabled_tags) do
+        node.render_to_output_buffer(context, output)
+      end
+    rescue UndefinedVariable, UndefinedDropMethod, UndefinedFilter => e
+      context.handle_error(e, node.line_number)
+    rescue ::StandardError => e
+      line_number = node.is_a?(String) ? nil : node.line_number
+      output << context.handle_error(e, line_number)
+    end
+
+    def disable_tags(context, tags, &block)
+      return yield if tags.empty?
+      context.registers[:disabled_tags].disable(tags, &block)
+    end
+
+    def raise_if_resource_limits_reached(context, length)
+      context.resource_limits.render_length += length
+      return unless context.resource_limits.reached?
+      raise MemoryError, "Memory limits exceeded"
+    end
+
+    def create_variable(token, parse_context)
+      token.scan(CONTENT_OF_VARIABLE) do |content|
+        markup = content.first
+        return Variable.new(markup, parse_context)
+      end
+      raise_missing_variable_terminator(token, parse_context)
+    end
+
+    def raise_missing_tag_terminator(token, parse_context)
+      raise SyntaxError, parse_context.locale.t("errors.syntax.tag_termination", token: token, tag_end: TAG_END.inspect)
+    end
+
+    def raise_missing_variable_terminator(token, parse_context)
+      raise SyntaxError, parse_context.locale.t("errors.syntax.variable_termination", token: token, tag_end: VARIABLE_END.inspect)
+    end
+
+    def registered_tags
+      Template.tags
+    end
+  end
+end

lib/liquid/condition.rb

@@ -1,55 +1,75 @@
+# 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,
     }
 
     def self.operators
       @@operators
     end
 
-    attr_reader :attachment
+    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 +84,24 @@ 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?(Liquid::Expression::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?(Liquid::Expression::MethodLiteral)
+        if left.respond_to?(right.method_name)
+          return left.send(right.method_name)
         else
           return nil
         end
@@ -90,31 +114,41 @@ 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'
@@ -13,28 +14,45 @@ module Liquid
   #
   #   context['bob']  #=> nil  class Context
   class Context
-    attr_reader :scopes, :errors, :registers, :environments, :resource_limits
+    attr_reader :scopes, :errors, :registers, :environments, :resource_limits, :static_registers, :static_environments
+    attr_accessor :exception_renderer, :template_name, :partial, :global_filter, :strict_variables, :strict_filters
 
-    def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = {})
-      @environments    = [environments].flatten
-      @scopes          = [(outer_scope || {})]
-      @registers       = registers
-      @errors          = []
-      @rethrow_errors  = rethrow_errors
-      @resource_limits = (resource_limits || {}).merge!({ :render_score_current => 0, :assign_score_current => 0 })
-      squash_instance_assigns_with_environments
-
-      @interrupts = []
+    # rubocop:disable Metrics/ParameterLists
+    def self.build(environments: {}, outer_scope: {}, registers: {}, rethrow_errors: false, resource_limits: nil, static_environments: {})
+      new(environments, outer_scope, registers, rethrow_errors, resource_limits, static_environments)
     end
 
-    def resource_limits_reached?
-      (@resource_limits[:render_length_limit] && @resource_limits[:render_length_current] > @resource_limits[:render_length_limit]) ||
-      (@resource_limits[:render_score_limit]  && @resource_limits[:render_score_current]  > @resource_limits[:render_score_limit] ) ||
-      (@resource_limits[:assign_score_limit]  && @resource_limits[:assign_score_current]  > @resource_limits[:assign_score_limit] )
+    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
+      squash_instance_assigns_with_environments
+
+      self.exception_renderer = Template.default_exception_renderer
+      if rethrow_errors
+        self.exception_renderer = ->(_e) { raise }
+      end
+
+      @interrupts    = []
+      @filters       = []
+      @global_filter = nil
+    end
+    # rubocop:enable Metrics/ParameterLists
+
+    def warnings
+      @warnings ||= []
     end
 
     def strainer
-      @strainer ||= Strainer.create(self)
+      @strainer ||= Strainer.create(self, @filters)
     end
 
     # Adds filters to this context.
@@ -43,17 +61,17 @@ module Liquid
     # for that
     def add_filters(filters)
       filters = [filters].flatten.compact
+      @filters += filters
+      @strainer = nil
+    end
 
-      filters.each do |f|
-        raise ArgumentError, "Expected module but got: #{f.class}" unless f.is_a?(Module)
-        Strainer.add_known_filter(f)
-        strainer.extend(f)
-      end
+    def apply_global_filter(obj)
+      global_filter.nil? ? obj : global_filter.call(obj)
     end
 
     # are there any not handled interrupts?
-    def has_interrupt?
-      @interrupts.any?
+    def interrupt?
+      !@interrupts.empty?
     end
 
     # push an interrupt to the stack. this interrupt is considered not handled.
@@ -66,26 +84,22 @@ module Liquid
       @interrupts.pop
     end
 
-    def handle_error(e)
+    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)
-      strainer.invoke(method, *args)
+      strainer.invoke(method, *args).to_liquid
     end
 
     # Push new local scope on the stack. use <tt>Context#stack</tt> instead
-    def push(new_scope={})
+    def push(new_scope = {})
       @scopes.unshift(new_scope)
-      raise StackLevelError, "Nesting too deep" if @scopes.length > 100
+      check_overflow
     end
 
     # Merge a hash of variables in the current local scope
@@ -107,13 +121,32 @@ module Liquid
     #   end
     #
     #   context['var]  #=> nil
-    def stack(new_scope={})
+    def stack(new_scope = {})
       push(new_scope)
       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
+
+      Context.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
+      end
+    end
+
     def clear_instance_assigns
       @scopes[0] = {}
     end
@@ -123,145 +156,106 @@ module Liquid
       @scopes[0][key] = value
     end
 
-    def [](key)
-      resolve(key)
+    # 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
+    # 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 [](expression)
+      evaluate(Expression.parse(expression))
     end
 
-    def has_key?(key)
-      resolve(key) != nil
+    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
+        try_variable_find_in_environments(key, raise_on_not_found: raise_on_not_found)
+      end
+
+      variable         = variable.to_liquid
+      variable.context = self if variable.respond_to?(:context=)
+
+      variable
+    end
+
+    def lookup_and_evaluate(obj, key, raise_on_not_found: true)
+      if @strict_variables && raise_on_not_found && obj.respond_to?(:key?) && !obj.key?(key)
+        raise Liquid::UndefinedVariable, "undefined variable #{key}"
+      end
+
+      value = obj[key]
+
+      if value.is_a?(Proc) && obj.respond_to?(:[]=)
+        obj[key] = value.arity == 0 ? value.call : value.call(self)
+      else
+        value
+      end
+    end
+
+    protected
+
+    attr_writer :base_scope_depth, :warnings, :errors, :strainer, :filters
+
     private
-      LITERALS = {
-        nil => nil, 'nil' => nil, 'null' => nil, '' => nil,
-        'true'  => true,
-        'false' => false,
-        'blank' => :blank?,
-        'empty' => :empty?
-      }
 
-      # 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
-      # 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)
-        if LITERALS.key?(key)
-          LITERALS[key]
-        else
-          case key
-          when /^'(.*)'$/ # Single quoted strings
-            $1
-          when /^"(.*)"$/ # Double quoted strings
-            $1
-          when /^(-?\d+)$/ # Integer and floats
-            $1.to_i
-          when /^\((\S+)\.\.(\S+)\)$/ # Ranges
-            (resolve($1).to_i..resolve($2).to_i)
-          when /^(-?\d[\d\.]+)$/ # Floats
-            $1.to_f
-          else
-            variable(key)
+    attr_reader :base_scope_depth
+
+    def try_variable_find_in_environments(key, raise_on_not_found:)
+      @environments.each do |environment|
+        found_variable = lookup_and_evaluate(environment, key, raise_on_not_found: raise_on_not_found)
+        if !found_variable.nil? || @strict_variables && raise_on_not_found
+          return found_variable
+        end
+      end
+      @static_environments.each do |environment|
+        found_variable = lookup_and_evaluate(environment, key, raise_on_not_found: raise_on_not_found)
+        if !found_variable.nil? || @strict_variables && raise_on_not_found
+          return found_variable
+        end
+      end
+      nil
+    end
+
+    def check_overflow
+      raise StackLevelError, "Nesting too deep" if overflow?
+    end
+
+    def overflow?
+      base_scope_depth + @scopes.length > Block::MAX_DEPTH
+    end
+
+    def internal_error
+      # raise and catch to set backtrace and cause on exception
+      raise Liquid::InternalError, 'internal'
+    rescue Liquid::InternalError => exc
+      exc
+    end
+
+    def squash_instance_assigns_with_environments
+      @scopes.last.each_key do |k|
+        @environments.each do |env|
+          if env.key?(k)
+            scopes.last[k] = lookup_and_evaluate(env, k)
+            break
           end
         end
       end
-
-      # 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) }
-        variable = nil
-
-        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.context = self if variable.respond_to?(:context=)
-
-        return 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)
-        end
-
-        if object = find_variable(first_part)
-
-          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 # variable
-
-      def lookup_and_evaluate(obj, key)
-        if (value = obj[key]).is_a?(Proc) && obj.respond_to?(:[]=)
-          obj[key] = (value.arity == 0) ? value.call : value.call(self)
-        else
-          value
-        end
-      end # lookup_and_evaluate
-
-      def squash_instance_assigns_with_environments
-        @scopes.last.each_key do |k|
-          @environments.each do |env|
-            if env.has_key?(k)
-              scopes.last[k] = lookup_and_evaluate(env, k)
-              break
-            end
-          end
-        end
-      end # squash_instance_assigns_with_environments
+    end # squash_instance_assigns_with_environments
   end # Context
-
 end # Liquid

lib/liquid/document.rb

@@ -1,17 +1,29 @@
+# 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 < BlockBody
+    def self.parse(tokens, parse_context)
+      doc = new
+      doc.parse(tokens, parse_context)
+      doc
     end
 
-    # There isn't a real delimiter
-    def block_delimiter
-      []
+    def parse(tokens, parse_context)
+      super do |end_tag_name, _end_tag_params|
+        unknown_tag(end_tag_name, parse_context) if end_tag_name
+      end
+    rescue SyntaxError => e
+      e.line_number ||= parse_context.line_number
+      raise
     end
 
-    # Document blocks don't need to be terminated since they are not actually opened
-    def assert_missing_delimitation!
+    def unknown_tag(tag, parse_context)
+      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
   end
 end

lib/liquid/drop.rb

@@ -1,7 +1,8 @@
+# frozen_string_literal: true
+
 require 'set'
 
 module Liquid
-
   # A drop in liquid is a class which allows you to export DOM like things to liquid.
   # Methods of drops are callable.
   # The main use for liquid drops is to implement lazy loaded objects.
@@ -19,43 +20,61 @@ module Liquid
   #   tmpl = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {%endfor%} '  )
   #   tmpl.render('product' => ProductDrop.new ) # will invoke top_sales query.
   #
-  # Your drop can either implement the methods sans any parameters or implement the before_method(name) method which is a
-  # catch all.
+  # Your drop can either implement the methods sans any parameters
+  # or implement the liquid_method_missing(name) method which is a catch all.
   class Drop
     attr_writer :context
 
-    EMPTY_STRING = ''.freeze
-
     # Catch all for the method
-    def before_method(method)
-      nil
+    def liquid_method_missing(method)
+      return nil unless @context&.strict_variables
+      raise Liquid::UndefinedDropMethod, "undefined method #{method}"
     end
 
     # called by liquid to invoke a drop
     def invoke_drop(method_or_key)
-      if method_or_key && method_or_key != EMPTY_STRING && self.class.invokable?(method_or_key)
+      if self.class.invokable?(method_or_key)
         send(method_or_key)
       else
-        before_method(method_or_key)
+        liquid_method_missing(method_or_key)
       end
     end
 
-    def has_key?(name)
+    def key?(_name)
       true
     end
 
+    def inspect
+      self.class.to_s
+    end
+
     def to_liquid
       self
     end
 
-    alias :[] :invoke_drop
+    def to_s
+      self.class.name
+    end
 
-    private
+    alias_method :[], :invoke_drop
 
     # Check for method existence without invoking respond_to?, which creates symbols
     def self.invokable?(method_name)
-      @invokable_methods ||= Set.new((public_instance_methods - Liquid::Drop.public_instance_methods).map(&:to_s))
-      @invokable_methods.include?(method_name.to_s)
+      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

@@ -1,12 +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
-  class MemoryError < 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)
+  TaintedError        = 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)
+  InternalError       = Class.new(Error)
 end

lib/liquid/expression.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Expression
+    class MethodLiteral
+      attr_reader :method_name, :to_s
+
+      def initialize(method_name, to_s)
+        @method_name = method_name
+        @to_s = to_s
+      end
+
+      def to_liquid
+        to_s
+      end
+    end
+
+    LITERALS = {
+      nil => nil, 'nil' => nil, 'null' => nil, '' => nil,
+      'true' => true,
+      'false' => false,
+      'blank' => MethodLiteral.new(:blank?, '').freeze,
+      'empty' => MethodLiteral.new(:empty?, '').freeze
+    }.freeze
+
+    SINGLE_QUOTED_STRING = /\A'(.*)'\z/m
+    DOUBLE_QUOTED_STRING = /\A"(.*)"\z/m
+    INTEGERS_REGEX       = /\A(-?\d+)\z/
+    FLOATS_REGEX         = /\A(-?\d[\d\.]+)\z/
+    RANGES_REGEX         = /\A\((\S+)\.\.(\S+)\)\z/
+
+    def self.parse(markup)
+      if LITERALS.key?(markup)
+        LITERALS[markup]
+      else
+        case markup
+        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
+          VariableLookup.parse(markup)
+        end
+      end
+    end
+  end
+end

lib/liquid/extensions.rb

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

lib/liquid/file_system.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Liquid
   # A Liquid file system is a way to let your templates retrieve other templates for use with the include tag.
   #
@@ -8,13 +10,13 @@ module Liquid
   #
   # Example:
   #
-  # Liquid::Template.file_system = Liquid::LocalFileSystem.new(template_path)
-  # liquid = Liquid::Template.parse(template)
+  #   Liquid::Template.file_system = Liquid::LocalFileSystem.new(template_path)
+  #   liquid = Liquid::Template.parse(template)
   #
   # This will parse the template with a LocalFileSystem implementation rooted at 'template_path'.
   class BlankFileSystem
     # Called by Liquid to retrieve a template file
-    def read_template_file(template_path, context)
+    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, context)
+    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 +1,44 @@
+# 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 :name, :length, :parentloop
+
+    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+(#{QuotedFragment}+)/o
-
-    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 ''
-
-      from = @attributes['offset'] ? context[@attributes['offset']].to_i : 0
-      to = @attributes['limit'] ? from + context[@attributes['limit']].to_i : nil
-
-      collection = Utils.slice_collection_using_each(collection, from, to)
-
-      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 (index != length - 1)
-            col  = 0
-            row += 1
-            result << "</tr>\n<tr class=\"row#{row}\">"
-          end
-
-        end
-      end
-      result << "</tr>\n"
-      result
-    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

@@ -1,10 +1,11 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # An interrupt is any command that breaks processing of a block (ex: a for loop).
   class Interrupt
     attr_reader :message
 
-    def initialize(message=nil)
+    def initialize(message = nil)
       @message = message || "interrupt"
     end
   end

lib/liquid/legacy.rb

@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+module Liquid
+  FilterSeparator            = FILTER_SEPARATOR
+  ArgumentSeparator          = ARGUMENT_SEPARATOR
+  FilterArgumentSeparator    = FILTER_ARGUMENT_SEPARATOR
+  VariableAttributeSeparator = VARIABLE_ATTRIBUTE_SEPARATOR
+  WhitespaceControl          = WHITESPACE_CONTROL
+  TagStart                   = TAG_START
+  TagEnd                     = TAG_END
+  VariableSignature          = VARIABLE_SIGNATURE
+  VariableSegment            = VARIABLE_SEGMENT
+  VariableStart              = VARIABLE_START
+  VariableEnd                = VARIABLE_END
+  VariableIncompleteEnd      = VARIABLE_INCOMPLETE_END
+  QuotedString               = QUOTED_STRING
+  QuotedFragment             = QUOTED_FRAGMENT
+  TagAttributes              = TAG_ATTRIBUTES
+  AnyStartingTag             = ANY_STARTING_TAG
+  PartialTemplateParser      = PARTIAL_TEMPLATE_PARSER
+  TemplateParser             = TEMPLATE_PARSER
+  VariableParser             = VARIABLE_PARSER
+
+  class BlockBody
+    FullToken           = FULL_TOKEN
+    ContentOfVariable   = CONTENT_OF_VARIABLE
+    WhitespaceOrNothing = WHITESPACE_OR_NOTHING
+    TAGSTART            = TAG_START_STRING
+    VARSTART            = VAR_START_STRING
+  end
+
+  class Assign < Tag
+    Syntax = SYNTAX
+  end
+
+  class Capture < Block
+    Syntax = SYNTAX
+  end
+
+  class Case < Block
+    Syntax     = SYNTAX
+    WhenSyntax = WHEN_SYNTAX
+  end
+
+  class Cycle < Tag
+    SimpleSyntax = SIMPLE_SYNTAX
+    NamedSyntax  = NAMED_SYNTAX
+  end
+
+  class For < Block
+    Syntax = SYNTAX
+  end
+
+  class If < Block
+    Syntax                  = SYNTAX
+    ExpressionsAndOperators = EXPRESSIONS_AND_OPERATORS
+  end
+
+  class Include < Tag
+    Syntax = SYNTAX
+  end
+
+  class Raw < Block
+    Syntax                   = SYNTAX
+    FullTokenPossiblyInvalid = FULL_TOKEN_POSSIBLY_INVALID
+  end
+
+  class TableRow < Block
+    Syntax = SYNTAX
+  end
+
+  class Variable
+    FilterMarkupRegex        = FILTER_MARKUP_REGEX
+    FilterParser             = FILTER_PARSER
+    FilterArgsRegex          = FILTER_ARGS_REGEX
+    JustTagAttributes        = JUST_TAG_ATTRIBUTES
+    MarkupWithQuotedFragment = MARKUP_WITH_QUOTED_FRAGMENT
+  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"
+      meta_syntax_error: "Liquid syntax error: #{e.message}"
+      table_row: "Syntax Error in 'table_row loop' - Valid syntax: table_row [item] in [collection] cols=3"
+      render: "Syntax error in tag 'render' - Template name must be a quoted string"
+    argument:
+      include: "Argument error in tag 'include' - Illegal template name"
+    disabled:
+      tag: "usage is not allowed in this context"

lib/liquid/module_ex.rb

@@ -1,62 +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 used in order to expose the object of the implementing class
-# to liquid as it were a Drop. It also limits the liquid-callable methods of the instance
-# to the allowed method passed with the liquid_methods call
-# Example:
-#
-# class SomeClass
-#   liquid_methods :an_allowed_method
-#
-#   def an_allowed_method
-#     'this comes from an allowed method'
-#   end
-#   def unallowed_method
-#     'this will never be an output'
-#   end
-# end
-#
-# if you want to extend the drop to other methods you can defines more methods
-# in the class <YourClass>::LiquidDropClass
-#
-#   class SomeClass::LiquidDropClass
-#     def another_allowed_method
-#       'and this from another allowed method'
-#     end
-#   end
-# 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 +1,42 @@
+# 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 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 +1,95 @@
+# 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
+
+    SINGLE_TOKEN_EXPRESSION_TYPES = [:string, :number].freeze
+    private_constant :SINGLE_TOKEN_EXPRESSION_TYPES
+
+    def expression
+      token = @tokens[@p]
+      if token[0] == :id
+        variable_signature
+      elsif SINGLE_TOKEN_EXPRESSION_TYPES.include?(token[0])
+        consume
+      elsif token.first == :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_signature
+      str = consume(:id)
+      while look(:open_square)
+        str << consume
+        str << expression
+        str << consume(:close_square)
+      end
+      if look(:dot)
+        str << consume
+        str << variable_signature
+      end
+      str
+    end
+  end
+end

lib/liquid/parser_switching.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Liquid
+  module ParserSwitching
+    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
+          return strict_parse_with_error_context(markup)
+        rescue SyntaxError => e
+          parse_context.warnings << e
+          return 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 +1,21 @@
+# 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
+
+      partial = Liquid::Template.parse(source, parse_context)
+      cached_partials[template_name] = partial
+    ensure
+      parse_context.partial = false
+    end
+  end
+end

lib/liquid/profiler.rb

@@ -0,0 +1,171 @@
+# 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.
+  #     # If top level, this will be "<root>".
+  #     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, :partial, :line_number, :children, :total_time, :self_time
+
+      def initialize(node, partial)
+        @code        = node.respond_to?(:raw) ? node.raw : node
+        @partial     = partial
+        @line_number = node.respond_to?(:line_number) ? node.line_number : nil
+        @children    = []
+      end
+
+      def self.start(node, partial)
+        new(node, partial).tap(&:start)
+      end
+
+      def start
+        @start_time = Time.now
+      end
+
+      def finish
+        @end_time   = Time.now
+        @total_time = @end_time - @start_time
+
+        if @children.empty?
+          @self_time = @total_time
+        else
+          total_children_time = 0
+          @children.each do |child|
+            total_children_time += child.total_time
+          end
+          @self_time = @total_time - total_children_time
+        end
+      end
+
+      def render_time
+        @end_time - @start_time
+      end
+    end
+
+    def self.profile_node_render(node)
+      if Profiler.current_profile && node.respond_to?(:render)
+        Profiler.current_profile.start_node(node)
+        output = yield
+        Profiler.current_profile.end_node(node)
+        output
+      else
+        yield
+      end
+    end
+
+    def self.profile_children(template_name)
+      if Profiler.current_profile
+        Profiler.current_profile.push_partial(template_name)
+        output = yield
+        Profiler.current_profile.pop_partial
+        output
+      else
+        yield
+      end
+    end
+
+    def self.current_profile
+      Thread.current[:liquid_profiler]
+    end
+
+    def initialize(partial_name = "<root>")
+      @partial_stack = [partial_name]
+
+      @root_timing  = Timing.new("", current_partial)
+      @timing_stack = [@root_timing]
+
+      @render_start_at = Time.now
+      @render_end_at   = @render_start_at
+    end
+
+    def start
+      Thread.current[:liquid_profiler] = self
+      @render_start_at = Time.now
+    end
+
+    def stop
+      Thread.current[:liquid_profiler] = nil
+      @render_end_at = Time.now
+    end
+
+    def total_render_time
+      @render_end_at - @render_start_at
+    end
+
+    def each(&block)
+      @root_timing.children.each(&block)
+    end
+
+    def [](idx)
+      @root_timing.children[idx]
+    end
+
+    def length
+      @root_timing.children.length
+    end
+
+    def start_node(node)
+      @timing_stack.push(Timing.start(node, current_partial))
+    end
+
+    def end_node(_node)
+      timing = @timing_stack.pop
+      timing.finish
+
+      @timing_stack.last.children << timing
+    end
+
+    def current_partial
+      @partial_stack.last
+    end
+
+    def push_partial(partial_name)
+      @partial_stack.push(partial_name)
+    end
+
+    def pop_partial
+      @partial_stack.pop
+    end
+  end
+end

lib/liquid/profiler/hooks.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Liquid
+  class BlockBody
+    def render_node_with_profiling(context, output, node)
+      Profiler.profile_node_render(node) do
+        render_node_without_profiling(context, output, node)
+      end
+    end
+
+    alias_method :render_node_without_profiling, :render_node
+    alias_method :render_node, :render_node_with_profiling
+  end
+
+  class Include < Tag
+    def render_to_output_buffer_with_profiling(context, output)
+      Profiler.profile_children(context.evaluate(@template_name_expr).to_s) do
+        render_to_output_buffer_without_profiling(context, output)
+      end
+    end
+
+    alias_method :render_to_output_buffer_without_profiling, :render_to_output_buffer
+    alias_method :render_to_output_buffer, :render_to_output_buffer_with_profiling
+  end
+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/registers/disabled_tags.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+module Liquid
+  class DisabledTags < Register
+    def initialize
+      @disabled_tags = {}
+    end
+
+    def disabled?(tag)
+      @disabled_tags.key?(tag) && @disabled_tags[tag] > 0
+    end
+
+    def disable(tags)
+      tags.each(&method(:increment))
+      yield
+    ensure
+      tags.each(&method(:decrement))
+    end
+
+    private
+
+    def increment(tag)
+      @disabled_tags[tag] ||= 0
+      @disabled_tags[tag]  += 1
+    end
+
+    def decrement(tag)
+      @disabled_tags[tag] -= 1
+    end
+  end
+
+  Template.add_register(:disabled_tags, DisabledTags.new)
+end

lib/liquid/resource_limits.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Liquid
+  class ResourceLimits
+    attr_accessor :render_length, :render_score, :assign_score,
+      :render_length_limit, :render_score_limit, :assign_score_limit
+
+    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 reached?
+      (@render_length_limit && @render_length > @render_length_limit) ||
+        (@render_score_limit && @render_score > @render_score_limit) ||
+        (@assign_score_limit && @assign_score > @assign_score_limit)
+    end
+
+    def reset
+      @render_length = @render_score = @assign_score = 0
+    end
+  end
+end

lib/liquid/standardfilters.rb

@@ -1,13 +1,27 @@
+# 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
 
@@ -27,32 +41,61 @@ module Liquid
     end
 
     def escape(input)
-      CGI.escapeHTML(input) rescue input
+      CGI.escapeHTML(input.to_s).untaint unless input.nil?
     end
+    alias_method :h, :escape
 
     def escape_once(input)
-      ActionView::Helpers::TagHelper.escape_once(input)
-    rescue NameError
-      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
-      truncated = RUBY_VERSION[0,3] == "1.8" ? input.scan(/./mu)[0...l].to_s : input[0...l]
-      input.length > length.to_i ? truncated + 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
+      return if input.nil?
       wordlist = input.to_s.split
-      l = words.to_i - 1
+      words    = Utils.to_integer(words)
+
+      l = words - 1
       l = 0 if l < 0
-      wordlist.length > l ? wordlist[0..l].join(" ") + truncate_string : input
+
+      wordlist.length > l ? wordlist[0..l].join(" ").concat(truncate_string.to_s) : input
     end
 
     # Split input string into an array of substrings separated by given pattern.
@@ -61,11 +104,26 @@ module Liquid
     #   <div class="summary">{{ post | split '//' | first }}</div>
     #
     def split(input, pattern)
-      input.split(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>/m, '').gsub(/<!--.*?-->/m, '').gsub(/<style.*?<\/style>/m, '').gsub(/<.*?>/m, '')
+      empty  = ''
+      result = input.to_s.gsub(STRIP_HTML_BLOCKS, empty)
+      result.gsub!(STRIP_HTML_TAGS, empty)
+      result
     end
 
     # Remove all newlines from the string
@@ -75,56 +133,147 @@ module Liquid
 
     # 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 = [input].flatten
+      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.to_s)
+      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.to_s)
+      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
@@ -132,6 +281,13 @@ 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
@@ -142,7 +298,7 @@ module Liquid
       input.to_s.gsub(/\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'')
@@ -156,6 +312,7 @@ 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
@@ -170,34 +327,14 @@ 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))
 
-      if ((input.is_a?(String) && !/^\d+$/.match(input.to_s).nil?) || input.is_a?(Integer)) && input.to_i > 0
-        input = Time.at(input.to_i)
-      end
-
-      date = if input.is_a?(String)
-        case input.downcase
-        when 'now', 'today'
-          Time.now
-        else
-          Time.parse(input)
-        end
-      else
-        input
-      end
-
-      if date.respond_to?(:strftime)
-        date.strftime(format.to_s)
-      else
-        input
-      end
-    rescue
-      input
+      date.strftime(format.to_s)
     end
 
     # Get the first element of the passed in array
@@ -218,6 +355,12 @@ module Liquid
       array.last if array.respond_to?(:last)
     end
 
+    # absolute value
+    def abs(input)
+      result = Utils.to_number(input).abs
+      result.is_a?(BigDecimal) ? result.to_f : result
+    end
+
     # addition
     def plus(input, operand)
       apply_operation(input, operand, :+)
@@ -236,31 +379,146 @@ module Liquid
     # division
     def divided_by(input, operand)
       apply_operation(input, operand, :/)
+    rescue ::ZeroDivisionError => e
+      raise Liquid::ZeroDivisionError, e.message
     end
 
     def modulo(input, operand)
       apply_operation(input, operand, :%)
+    rescue ::ZeroDivisionError => e
+      raise Liquid::ZeroDivisionError, e.message
+    end
+
+    def round(input, n = 0)
+      result = 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 Float
-        BigDecimal.new(obj.to_s)
-      when Numeric
-        obj
-      when String
-        (obj.strip =~ /^\d+\.\d+$/) ? BigDecimal.new(obj) : obj.to_i
-      else
-        0
-      end
+    attr_reader :context
+
+    def raise_property_error(property)
+      raise Liquid::ArgumentError, "cannot select the property '#{property}'"
     end
 
     def apply_operation(input, operand, operation)
-      result = to_number(input).send(operation, to_number(operand))
+      result = Utils.to_number(input).send(operation, Utils.to_number(operand))
       result.is_a?(BigDecimal) ? result.to_f : result
     end
+
+    def nil_safe_compare(a, b)
+      if !a.nil? && !b.nil?
+        a <=> b
+      else
+        a.nil? ? 1 : -1
+      end
+    end
+
+    def nil_safe_casecmp(a, b)
+      if !a.nil? && !b.nil?
+        a.to_s.casecmp(b.to_s)
+      else
+        a.nil? ? 1 : -1
+      end
+    end
+
+    class InputIterator
+      include Enumerable
+
+      def initialize(input, 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 +1,36 @@
+# frozen_string_literal: true
+
+module Liquid
+  class StaticRegisters
+    attr_reader :static, :registers
+
+    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
+
+    def fetch(key, default = nil)
+      key?(key) ? self[key] : default
+    end
+
+    def key?(key)
+      @registers.key?(key) || @static.key?(key)
+    end
+  end
+end

lib/liquid/strainer.rb

@@ -1,53 +1,68 @@
+# frozen_string_literal: true
+
 require 'set'
 
 module Liquid
-
   # Strainer is the parent class for the filters system.
   # New filters are mixed into the strainer class which is then instantiated for each liquid template render run.
   #
   # The Strainer only allows method calls defined in filters given to it via Strainer.global_filter,
   # Context#add_filters or Template.register_filter
   class Strainer #:nodoc:
-    @@filters = []
-    @@known_filters = Set.new
-    @@known_methods = Set.new
+    @@global_strainer = Class.new(Strainer) do
+      @filter_methods = Set.new
+    end
+    @@strainer_class_cache = Hash.new do |hash, filters|
+      hash[filters] = Class.new(@@global_strainer) do
+        @filter_methods = @@global_strainer.filter_methods.dup
+        filters.each { |f| add_filter(f) }
+      end
+    end
 
     def initialize(context)
       @context = context
     end
 
-    def self.global_filter(filter)
-      raise ArgumentError, "Passed filter is not a module" unless filter.is_a?(Module)
-      add_known_filter(filter)
-      @@filters << filter unless @@filters.include?(filter)
+    class << self
+      attr_reader :filter_methods
     end
 
-    def self.add_known_filter(filter)
-      unless @@known_filters.include?(filter)
-        @@method_blacklist ||= Set.new(Strainer.instance_methods.map(&:to_s))
-        new_methods = filter.instance_methods.map(&:to_s)
-        new_methods.reject!{ |m| @@method_blacklist.include?(m) }
-        @@known_methods.merge(new_methods)
-        @@known_filters.add(filter)
+    def self.add_filter(filter)
+      raise ArgumentError, "Expected module but got: #{filter.class}" unless filter.is_a?(Module)
+      unless 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(', ')}"
+        else
+          send(:include, filter)
+          @filter_methods.merge(filter.public_instance_methods.map(&:to_s))
+        end
       end
     end
 
-    def self.create(context)
-      strainer = Strainer.new(context)
-      @@filters.each { |m| strainer.extend(m) }
-      strainer
+    def self.global_filter(filter)
+      @@strainer_class_cache.clear
+      @@global_strainer.add_filter(filter)
+    end
+
+    def self.invokable?(method)
+      @filter_methods.include?(method.to_s)
+    end
+
+    def self.create(context, filters = [])
+      @@strainer_class_cache[filters].new(context)
     end
 
     def invoke(method, *args)
-      if invokable?(method)
+      if self.class.invokable?(method)
         send(method, *args)
+      elsif @context&.strict_filters
+        raise Liquid::UndefinedFilter, "undefined filter #{method}"
       else
         args.first
       end
-    end
-
-    def invokable?(method)
-      @@known_methods.include?(method.to_s) && respond_to?(method)
+    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 +1,73 @@
+# frozen_string_literal: true
+
 module Liquid
-
   class Tag
+    attr_reader :nodelist, :tag_name, :line_number, :parse_context
+    alias_method :options, :parse_context
+    include ParserSwitching
 
-    attr_accessor :nodelist
+    class << self
+      def parse(tag_name, markup, tokenizer, parse_context)
+        tag = new(tag_name, markup, parse_context)
+        tag.parse(tokenizer)
+        tag
+      end
 
-    def initialize(tag_name, markup, tokens)
-      @tag_name   = tag_name
-      @markup     = markup
-      parse(tokens)
+      def disable_tags(*tags)
+        disabled_tags.push(*tags)
+      end
+
+      private :new
+
+      def disabled_tags
+        @disabled_tags ||= []
+      end
     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
 
-  end # Tag
+    def disabled?(context)
+      context.registers[:disabled_tags].disabled?(tag_name)
+    end
 
-end # Liquid
+    def disabled_error_message
+      "#{tag_name} #{options[:locale].t('errors.disabled.tag')}"
+    end
+
+    # For backwards compatibility with custom tags. In a future release, the semantics
+    # of the `render_to_output_buffer` method will become the default and the `render`
+    # method will be removed.
+    def render_to_output_buffer(context, output)
+      output << render(context)
+      output
+    end
+
+    def blank?
+      false
+    end
+
+    def disabled_tags
+      self.class.disabled_tags
+    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' %}
@@ -9,26 +10,55 @@ module Liquid
   #  {{ foo }}
   #
   class Assign < Tag
-    Syntax = /(#{VariableSignature}+)\s*=\s*(.*)\s*/o
+    SYNTAX = /(#{VARIABLE_SIGNATURE}+)\s*=\s*(.*)\s*/om
 
-    def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
-        @to = $1
-        @from = Variable.new($2)
-      else
-        raise SyntaxError.new("Syntax Error in 'assign' - Valid syntax: assign [var] = [source]")
-      end
-
-      super
+    def self.syntax_error_translation_key
+      "errors.syntax.assign"
     end
 
-    def render(context)
+    attr_reader :to, :from
+
+    def initialize(tag_name, markup, options)
+      super
+      if markup =~ SYNTAX
+        @to = Regexp.last_match(1)
+        @from = Variable.new(Regexp.last_match(2), options)
+      else
+        raise SyntaxError, options[:locale].t(self.class.syntax_error_translation_key)
+      end
+    end
+
+    def render_to_output_buffer(context, output)
       val = @from.render(context)
       context.scopes.last[@to] = val
-      context.resource_limits[:assign_score_current] += (val.respond_to?(:length) ? val.length : 1)
-      ''
+      context.resource_limits.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) || val.instance_of?(Hash)
+        sum = 1
+        # Uses #each to avoid extra allocations.
+        val.each { |child| sum += assign_score_of(child) }
+        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

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Break tag to be used to break out of a for loop.
   #
   # == Basic Usage:
@@ -10,11 +11,9 @@ module Liquid
   #    {% endfor %}
   #
   class Break < Tag
-
     def interrupt
       BreakInterrupt.new
     end
-
   end
 
   Template.register_tag('break', Break)

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 %}
@@ -12,23 +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 = /(#{VARIABLE_SIGNATURE}+)/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
+    def render_to_output_buffer(context, output)
+      previous_output_size = output.bytesize
+      super
       context.scopes.last[@to] = output
-      context.resource_limits[:assign_score_current] += (output.respond_to?(:length) ? output.length : 1)
-      ''
+      context.resource_limits.assign_score += (output.bytesize - previous_output_size)
+      output
+    end
+
+    def blank?
+      true
     end
   end
 

lib/liquid/tags/case.rb

@@ -1,22 +1,33 @@
+# frozen_string_literal: true
+
 module Liquid
   class Case < Block
-    Syntax     = /(#{QuotedFragment})/o
-    WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/o
+    SYNTAX = /(#{QUOTED_FRAGMENT})/o
+    WHEN_SYNTAX = /(#{QUOTED_FRAGMENT})(?:(?:\s+or\s+|\s*\,\s*)(#{QUOTED_FRAGMENT}.*))?/om
 
-    def initialize(tag_name, markup, tokens)
+    attr_reader :blocks, :left
+
+    def initialize(tag_name, markup, options)
+      super
       @blocks = []
 
-      if markup =~ Syntax
-        @left = $1
+      if markup =~ SYNTAX
+        @left = Expression.parse(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 = BlockBody.new
+      body = @blocks.last.attachment while parse_body(body, tokens)
+    end
+
+    def nodelist
+      @blocks.map(&:attachment)
     end
 
     def unknown_tag(tag, markup, tokens)
-      @nodelist = []
       case tag
       when 'when'
         record_when_condition(markup)
@@ -27,52 +38,54 @@ 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
 
-        output = ''
-        @blocks.each do |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
+      @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
-        output
       end
+
+      output
     end
 
     private
 
     def record_when_condition(markup)
+      body = BlockBody.new
+
       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...] %} ")
+        unless markup =~ WHEN_SYNTAX
+          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, '==', Expression.parse(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(BlockBody.new)
       @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

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Continue tag to be used to break out of a for loop.
   #
   # == Basic Usage:
@@ -10,11 +11,9 @@ module Liquid
   #    {% endfor %}
   #
   class Continue < Tag
-
     def interrupt
       ContinueInterrupt.new
     end
-
   end
 
   Template.register_tag('continue', Continue)

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}+/o
-    NamedSyntax  = /^(#{QuotedFragment})\s*\:\s*(.*)/o
+    SIMPLE_SYNTAX = /\A#{QUOTED_FRAGMENT}+/o
+    NAMED_SYNTAX  = /\A(#{QUOTED_FRAGMENT})\s*\:\s*(.*)/om
 
-    def initialize(tag_name, markup, tokens)
-      case markup
-      when NamedSyntax
-        @variables = variables_from_string($2)
-        @name = $1
-      when SimpleSyntax
-        @variables = variables_from_string(markup)
-        @name = "'#{@variables.to_s}'"
-      else
-        raise SyntaxError.new("Syntax Error in 'cycle' - Valid syntax: cycle [name :] var [, var2, var3 ...]")
-      end
+    attr_reader :variables
+
+    def initialize(tag_name, markup, options)
       super
+      case markup
+      when NAMED_SYNTAX
+        @variables = variables_from_string(Regexp.last_match(2))
+        @name      = Expression.parse(Regexp.last_match(1))
+      when SIMPLE_SYNTAX
+        @variables = variables_from_string(markup)
+        @name      = @variables.to_s
+      else
+        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
+      end
     end
 
-    def render(context)
-      context.registers[:cycle] ||= Hash.new(0)
+    def render_to_output_buffer(context, output)
+      context.registers[:cycle] ||= {}
 
-      context.stack do
-        key = context[@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*/o
-        $1 ? $1 : nil
+        var =~ /\s*(#{QUOTED_FRAGMENT})\s*/o
+        Regexp.last_match(1) ? Expression.parse(Regexp.last_match(1)) : nil
       end.compact
     end
 
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        Array(@node.variables)
+      end
+    end
   end
 
   Template.register_tag('cycle', Cycle)

lib/liquid/tags/decrement.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # decrement is used in a place where one needs to insert a counter
   #     into a template, and needs the counter to survive across
   #     multiple instantiations of the template.
@@ -19,20 +20,18 @@ module Liquid
   #    Hello: -3
   #
   class Decrement < Tag
-    def initialize(tag_name, markup, tokens)
-      @variable = markup.strip
-
+    def initialize(tag_name, markup, options)
       super
+      @variable = markup.strip
     end
 
-    def render(context)
+    def render_to_output_buffer(context, output)
       value = context.environments.first[@variable] ||= 0
-      value = value - 1
+      value -= 1
       context.environments.first[@variable] = value
-      value.to_s
+      output << value.to_s
+      output
     end
-
-    private
   end
 
   Template.register_tag('decrement', Decrement)

lib/liquid/tags/echo.rb

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

lib/liquid/tags/for.rb

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # "For" iterates over an array or collection.
   # Several useful variables are available to you within the loop.
   #
@@ -24,7 +25,7 @@ module Liquid
   #      {{ item.name }}
   #    {% end %}
   #
-  #  To reverse the for loop simply use {% for item in collection reversed %}
+  #  To reverse the for loop simply use {% for item in collection reversed %} (note that the flag's spelling is different to the filter `reverse`)
   #
   # == Available variables:
   #
@@ -42,100 +43,176 @@ 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 = /\A(\w+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
+    SYNTAX = /\A(#{VARIABLE_SEGMENT}+)\s+in\s+(#{QUOTED_FRAGMENT}+)\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
 
-      @nodelist = @for_block = []
+    def initialize(tag_name, markup, options)
       super
+      @from = @limit = nil
+      parse_with_selected_parser(markup)
+      @for_block = BlockBody.new
+      @else_block = nil
+    end
+
+    def parse(tokens)
+      return unless parse_body(@for_block, tokens)
+      parse_body(@else_block, tokens)
+    end
+
+    def nodelist
+      @else_block ? [@for_block, @else_block] : [@for_block]
     end
 
     def unknown_tag(tag, markup, tokens)
       return super unless tag == 'else'
-      @nodelist = @else_block = []
+      @else_block = BlockBody.new
     end
 
-    def render(context)
-      context.registers[:for] ||= Hash.new(0)
+    def render_to_output_buffer(context, output)
+      segment = collection_segment(context)
 
-      collection = context[@collection_name]
-      collection = collection.to_a if collection.is_a?(Range)
-
-      # Maintains Ruby 1.8.7 String#each behaviour on 1.9
-      return render_else(context) unless iterable?(collection)
-
-      from = if @attributes['offset'] == 'continue'
-        context.registers[:for][@name].to_i
+      if segment.empty?
+        render_else(context, output)
       else
-        context[@attributes['offset']].to_i
+        render_segment(context, output, segment)
       end
 
-      limit = context[@attributes['limit']]
-      to    = limit ? limit.to_i + from : nil
+      output
+    end
 
+    protected
 
-      segment = Utils.slice_collection_using_each(collection, from, to)
-
-      return render_else(context) if segment.empty?
-
-      segment.reverse! if @reversed
-
-      result = ''
-
-      length = segment.length
-
-      # Store our progress through the collection for the continue flag
-      context.registers[:for][@name] = from + segment.length
-
-      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(@for_block, context)
-
-          # Handle any interrupts if they exist.
-          if context.has_interrupt?
-            interrupt = context.pop_interrupt
-            break if interrupt.is_a? BreakInterrupt
-            next if interrupt.is_a? ContinueInterrupt
-          end
+    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 = Expression.parse(collection_name)
+        markup.scan(TAG_ATTRIBUTES) do |key, value|
+          set_attribute(key, value)
         end
+      else
+        raise SyntaxError, options[:locale].t("errors.syntax.for")
       end
-      result
+    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 = Expression.parse(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 render_else(context)
-        return @else_block ? [render_all(@else_block, context)] : ''
+    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
 
-      def iterable?(collection)
-        collection.respond_to?(:each) || Utils.non_blank_string?(collection)
+      collection = context.evaluate(@collection_name)
+      collection = collection.to_a if collection.is_a?(Range)
+
+      limit_value = context.evaluate(@limit)
+      to = if limit_value.nil?
+        nil
+      else
+        Utils.to_integer(limit_value) + from
       end
+
+      segment = Utils.slice_collection(collection, from, to)
+      segment.reverse! if @reversed
+
+      offsets[@name] = from + segment.length
+
+      segment
+    end
+
+    def render_segment(context, output, segment)
+      for_stack = context.registers[:for_stack] ||= []
+      length    = segment.length
+
+      context.stack do
+        loop_vars = Liquid::ForloopDrop.new(@name, length, for_stack[-1])
+
+        for_stack.push(loop_vars)
+
+        begin
+          context['forloop'] = loop_vars
+
+          segment.each do |item|
+            context[@variable_name] = item
+            @for_block.render_to_output_buffer(context, output)
+            loop_vars.send(:increment!)
+
+            # Handle any interrupts if they exist.
+            next unless context.interrupt?
+            interrupt = context.pop_interrupt
+            break if interrupt.is_a?(BreakInterrupt)
+            next if interrupt.is_a?(ContinueInterrupt)
+          end
+        ensure
+          for_stack.pop
+        end
+      end
+
+      output
+    end
+
+    def set_attribute(key, expr)
+      case key
+      when 'offset'
+        @from = if expr == 'continue'
+          :continue
+        else
+          Expression.parse(expr)
+        end
+      when 'limit'
+        @limit = Expression.parse(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
 
   Template.register_tag('for', For)

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 %}
@@ -10,18 +11,26 @@ 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})?/o
-    ExpressionsAndOperators = /(?:\b(?:\s?and\s?|\s?or\s?)\b|(?:\s*(?!\b(?:\s?and\s?|\s?or\s?)\b)(?:#{QuotedFragment}|\S+)\s*)+)/o
+    SYNTAX                    = /(#{QUOTED_FRAGMENT})\s*([=!<>a-z_]+)?\s*(#{QUOTED_FRAGMENT})?/o
+    EXPRESSIONS_AND_OPERATORS = /(?:\b(?:\s?and\s?|\s?or\s?)\b|(?:\s*(?!\b(?:\s?and\s?|\s?or\s?)\b)(?:#{QUOTED_FRAGMENT}|\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
     end
 
     def unknown_tag(tag, markup, tokens)
@@ -32,47 +41,82 @@ module Liquid
       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
 
-      def push_block(tag, markup)
-        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).to_s.strip
-
-            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
-        end
-
-        @blocks.push(block)
-        @nodelist = block.attach(Array.new)
+    def push_block(tag, markup)
+      block = if tag == 'else'
+        ElseCondition.new
+      else
+        parse_with_selected_parser(markup)
       end
 
+      @blocks.push(block)
+      block.attach(BlockBody.new)
+    end
 
+    def lax_parse(markup)
+      expressions = markup.scan(EXPRESSIONS_AND_OPERATORS)
+      raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop =~ SYNTAX
+
+      condition = Condition.new(Expression.parse(Regexp.last_match(1)), Regexp.last_match(2), Expression.parse(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(Expression.parse(Regexp.last_match(1)), Regexp.last_match(2), Expression.parse(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 = Expression.parse(p.expression)
+      if (op = p.consume?(:comparison))
+        b = Expression.parse(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

@@ -1,5 +1,6 @@
-module Liquid
+# frozen_string_literal: true
 
+module Liquid
   # Include allows templates to relate with other templates
   #
   # Simply include another template:
@@ -15,78 +16,92 @@ module Liquid
   #   {% include 'product' for products %}
   #
   class Include < Tag
-    Syntax = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?/o
+    SYNTAX = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
 
-    def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
+    attr_reader :template_name_expr, :variable_name_expr, :attributes
 
-        @template_name = $1
-        @variable_name = $3
-        @attributes    = {}
+    def initialize(tag_name, markup, options)
+      super
 
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = value
+      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 ? Expression.parse(variable_name) : nil
+        @template_name_expr = Expression.parse(template_name)
+        @attributes         = {}
+
+        markup.scan(TAG_ATTRIBUTES) do |key, value|
+          @attributes[key] = Expression.parse(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)
-      partial = load_cached_partial(context)
-      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 |var|
-            context[@template_name[1..-2]] = var
-            partial.render(context)
+      old_template_name = context.template_name
+      old_partial       = context.partial
+      begin
+        context.template_name = template_name
+        context.partial       = true
+        context.stack do
+          @attributes.each do |key, value|
+            context[key] = context.evaluate(value)
+          end
+
+          if variable.is_a?(Array)
+            variable.each do |var|
+              context[context_variable_name] = var
+              partial.render_to_output_buffer(context, output)
+            end
+          else
+            context[context_variable_name] = variable
+            partial.render_to_output_buffer(context, output)
           end
-        else
-          context[@template_name[1..-2]] = variable
-          partial.render(context)
         end
+      ensure
+        context.template_name = old_template_name
+        context.partial       = old_partial
       end
+
+      output
     end
 
-    private
-      def load_cached_partial(context)
-        cached_partials = context.registers[:cached_partials] || {}
-        template_name = context[@template_name]
+    alias_method :parse_context, :options
+    private :parse_context
 
-        if cached = cached_partials[template_name]
-          return cached
-        end
-        source = read_template_from_file_system(context)
-        partial = Liquid::Template.parse(source)
-        cached_partials[template_name] = partial
-        context.registers[:cached_partials] = cached_partials
-        partial
-      end
-
-      def read_template_from_file_system(context)
-        file_system = context.registers[:file_system] || Liquid::Template.file_system
-
-        # make read_template_file call backwards-compatible.
-        case file_system.method(:read_template_file).arity
-        when 1
-          file_system.read_template_file(context[@template_name])
-        when 2
-          file_system.read_template_file(context[@template_name], context)
-        else
-          raise ArgumentError, "file_system.read_template_file expects two parameters: (template_name, context)"
-        end
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.template_name_expr,
+          @node.variable_name_expr,
+        ] + @node.attributes.values
       end
+    end
   end
 
   Template.register_tag('include', Include)

lib/liquid/tags/increment.rb

@@ -1,12 +1,13 @@
-module Liquid
+# 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:
@@ -16,19 +17,18 @@ module Liquid
   #    Hello: 2
   #
   class Increment < Tag
-    def initialize(tag_name, markup, tokens)
-      @variable = markup.strip
-
+    def initialize(tag_name, markup, options)
       super
+      @variable = markup.strip
     end
 
-    def render(context)
+    def render_to_output_buffer(context, output)
       value = context.environments.first[@variable] ||= 0
       context.environments.first[@variable] = value + 1
-      value.to_s
-    end
 
-    private
+      output << value.to_s
+      output
+    end
   end
 
   Template.register_tag('increment', Increment)

lib/liquid/tags/raw.rb

@@ -1,19 +1,47 @@
+# frozen_string_literal: true
+
 module Liquid
   class Raw < Block
-    FullTokenPossiblyInvalid = /^(.*)#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}$/o
+    SYNTAX = /\A\s*\z/
+    FULL_TOKEN_POSSIBLY_INVALID = /\A(.*)#{TAG_START}\s*(\w+)\s*(.*)?#{TAG_END}\z/om
+
+    def initialize(tag_name, markup, parse_context)
+      super
+
+      ensure_valid_markup(tag_name, markup, parse_context)
+    end
 
     def parse(tokens)
-      @nodelist ||= []
-      @nodelist.clear
-      while token = tokens.shift
-        if token =~ FullTokenPossiblyInvalid
-          @nodelist << $1 if $1 != ""
-          if block_delimiter == $2
-            end_tag
-            return
-          end
+      @body = +''
+      while (token = tokens.shift)
+        if token =~ FULL_TOKEN_POSSIBLY_INVALID
+          @body << Regexp.last_match(1) if Regexp.last_match(1) != ""
+          return if block_delimiter == Regexp.last_match(2)
         end
-        @nodelist << token if not token.empty?
+        @body << token unless token.empty?
+      end
+
+      raise SyntaxError, parse_context.locale.t("errors.syntax.tag_never_closed", block_name: 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

lib/liquid/tags/render.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Render < Tag
+    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)
+      variable_name = Regexp.last_match(3)
+
+      @alias_name = Regexp.last_match(5)
+      @variable_name_expr = variable_name ? Expression.parse(variable_name) : nil
+      @template_name_expr = Expression.parse(template_name)
+
+      @attributes = {}
+      markup.scan(TAG_ATTRIBUTES) do |key, value|
+        @attributes[key] = Expression.parse(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 variable.is_a?(Array)
+        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+(#{QUOTED_FRAGMENT}+)/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 = Expression.parse(Regexp.last_match(2))
+        @attributes      = {}
+        markup.scan(TAG_ATTRIBUTES) do |key, value|
+          @attributes[key] = Expression.parse(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 )
-        first_block = @blocks.first
-        unless first_block.evaluate(context)
-          return render_all(first_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.
@@ -14,10 +15,67 @@ module Liquid
   #   template.render('user_name' => 'bob')
   #
   class Template
-    attr_accessor :root, :resource_limits
+    attr_accessor :root
+    attr_reader :resource_limits, :warnings
+
     @@file_system = BlankFileSystem.new
 
+    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
+      # 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_writer :error_mode
+
+      # Sets how strict the taint checker should be.
+      # :lax is the default, and ignores the taint flag completely
+      # :warn adds a warning, but does not interrupt the rendering
+      # :error raises an error when tainted output is used
+      attr_writer :taint_mode
+
+      attr_accessor :default_exception_renderer
+      Template.default_exception_renderer = lambda do |exception|
+        exception
+      end
+
       def file_system
         @@file_system
       end
@@ -31,7 +89,23 @@ module Liquid
       end
 
       def tags
-        @tags ||= {}
+        @tags ||= TagRegistry.new
+      end
+
+      def add_register(name, klass)
+        registers[name.to_sym] = klass
+      end
+
+      def registers
+        @registers ||= {}
+      end
+
+      def error_mode
+        @error_mode ||= :lax
+      end
+
+      def taint_mode
+        @taint_mode ||= :lax
       end
 
       # Pass a module with filter methods which should be available
@@ -40,23 +114,33 @@ module Liquid
         Strainer.global_filter(mod)
       end
 
+      def default_resource_limits
+        @default_resource_limits ||= {}
+      end
+
       # creates a new <tt>Template</tt> object from liquid source code
-      def parse(source)
+      # To enable profiling, pass in <tt>profile: true</tt> as an option.
+      # See Liquid::Profiler for more information
+      def parse(source, options = {})
         template = Template.new
-        template.parse(source)
-        template
+        template.parse(source, options)
       end
     end
 
-    # creates a new <tt>Template</tt> from an array of tokens. Use <tt>Template.parse</tt> instead
     def initialize
-      @resource_limits = {}
+      @rethrow_errors  = false
+      @resource_limits = ResourceLimits.new(self.class.default_resource_limits)
     end
 
     # Parse source code.
     # Returns self for easy chaining
-    def parse(source)
-      @root = Document.new(tokenize(source))
+    def parse(source, options = {})
+      @options      = options
+      @profiling    = options[:profile]
+      @line_numbers = options[:line_numbers] || @profiling
+      parse_context = options.is_a?(ParseContext) ? options : ParseContext.new(options)
+      @root         = Document.parse(tokenize(source), parse_context)
+      @warnings     = parse_context.warnings
       self
     end
 
@@ -81,6 +165,9 @@ 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
@@ -92,41 +179,55 @@ module Liquid
 
       context = case args.first
       when Liquid::Context
-        args.shift
+        c = args.shift
+
+        if @rethrow_errors
+          c.exception_renderer = ->(_e) { raise }
+        end
+
+        c
       when Liquid::Drop
-        drop = args.shift
+        drop         = args.shift
         drop.context = Context.new([drop, assigns], instance_assigns, registers, @rethrow_errors, @resource_limits)
       when Hash
         Context.new([args.shift, assigns], instance_assigns, registers, @rethrow_errors, @resource_limits)
       when nil
         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
-
-      when Module
-        context.add_filters(args.pop)
-      when Array
+        apply_options_to_context(context, options)
+      when Module, Array
         context.add_filters(args.pop)
       end
 
+      Template.registers.each do |key, register|
+        context_register[key] = register
+      end
+
+      # Retrying a render resets resource usage
+      context.resource_limits.reset
+
       begin
         # render the nodelist.
         # for performance reasons we get an array back here. join will make a string out of it.
-        result = @root.render(context)
-        result.respond_to?(:join) ? result.join : result
+        with_profiling(context) do
+          @root.render_to_output_buffer(context, output || +'')
+        end
       rescue Liquid::MemoryError => e
         context.handle_error(e)
       ensure
@@ -135,22 +236,43 @@ module Liquid
     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)
-
-      # removes the rogue empty element at the beginning of the array
-      tokens.shift if tokens[0] and tokens[0].empty?
-
-      tokens
+      Tokenizer.new(source, @line_numbers)
     end
 
+    def with_profiling(context)
+      if @profiling && !context.partial
+        raise "Profiler not loaded, require 'liquid/profiler' first" unless defined?(Liquid::Profiler)
+
+        @profiler = Profiler.new(context.template_name)
+        @profiler.start
+
+        begin
+          yield
+        ensure
+          @profiler.stop
+        end
+      else
+        yield
+      end
+    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/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(TEMPLATE_PARSER)
+
+      # removes the rogue empty element at the beginning of the array
+      tokens.shift if tokens[0]&.empty?
+
+      tokens
+    end
+  end
+end

lib/liquid/usage.rb

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

lib/liquid/utils.rb

@@ -1,14 +1,26 @@
+# frozen_string_literal: true
+
 module Liquid
   module Utils
+    def self.slice_collection(collection, from, to)
+      if (from != 0 || !to.nil?) && collection.respond_to?(:load_slice)
+        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
+      index    = 0
 
       # Maintains Ruby 1.8.7 String#each behaviour on 1.9
-      return [collection] if non_blank_string?(collection)
+      if collection.is_a?(String)
+        return collection.empty? ? [] : [collection]
+      end
+      return [] unless collection.respond_to?(:each)
 
       collection.each do |item|
-
         if to && to <= index
           break
         end
@@ -23,8 +35,51 @@ module Liquid
       segments
     end
 
-    def self.non_blank_string?(collection)
-      collection.is_a?(String) && collection != ''
+    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
   #
@@ -11,46 +12,158 @@ module Liquid
   #   {{ user | link }}
   #
   class Variable
-    FilterParser = /(?:#{FilterSeparator}|(?:\s*(?:#{QuotedFragment}|#{ArgumentSeparator})\s*)+)/o
-    attr_accessor :filters, :name
+    FILTER_MARKUP_REGEX         = /#{FILTER_SEPARATOR}\s*(.*)/om
+    FILTER_PARSER               = /(?:\s+|#{QUOTED_FRAGMENT}|#{ARGUMENT_SEPARATOR})+/o
+    FILTER_ARGS_REGEX .         = /(?:#{FILTER_ARGUMENT_SEPARATOR}|#{ARGUMENT_SEPARATOR})\s*((?:\w+\s*\:\s*)?#{QUOTED_FRAGMENT})/o
+    JUST_TAG_ATTRIBUTES         = /\A#{TAG_ATTRIBUTES}\z/o
+    MARKUP_WITH_QUOTED_FRAGMENT = /(#{QUOTED_FRAGMENT})(.*)/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
+
+      parse_with_selected_parser(markup)
+    end
+
+    def raw
+      @markup
+    end
+
+    def markup_context(markup)
+      "in \"{{#{markup}}}\""
+    end
+
+    def lax_parse(markup)
       @filters = []
-      if match = markup.match(/\s*(#{QuotedFragment})(.*)/o)
-        @name = match[1]
-        if match[2].match(/#{FilterSeparator}\s*(.*)/o)
-          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*((?:\w+\s*\:\s*)?#{QuotedFragment})/o).flatten
-              @filters << [filtername, filterargs]
-            end
-          end
+      return unless markup =~ MARKUP_WITH_QUOTED_FRAGMENT
+
+      name_markup   = Regexp.last_match(1)
+      filter_markup = Regexp.last_match(2)
+      @name         = Expression.parse(name_markup)
+      if filter_markup =~ FILTER_MARKUP_REGEX
+        filters = Regexp.last_match(1).scan(FILTER_PARSER)
+        filters.each do |f|
+          next unless f =~ /\w+/
+          filtername = Regexp.last_match(0)
+          filterargs = f.scan(FILTER_ARGS_REGEX).flatten
+          @filters << parse_filter_expressions(filtername, filterargs)
         end
       end
     end
 
+    def strict_parse(markup)
+      @filters = []
+      p = Parser.new(markup)
+
+      @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 = []
-        keyword_args = {}
-        filter[1].to_a.each do |a|
-          if matches = a.match(/\A#{TagAttributes}\z/o)
-            keyword_args[matches[1]] = context[matches[2]]
-          else
-            filterargs << context[a]
-          end
+      obj = @filters.inject(context.evaluate(@name)) do |output, (filter_name, filter_args, filter_kwargs)|
+        filter_args = evaluate_filter_expressions(context, filter_args, filter_kwargs)
+        context.invoke(filter_name, output, *filter_args)
+      end
+
+      obj = context.apply_global_filter(obj)
+      taint_check(context, obj)
+      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(JUST_TAG_ATTRIBUTES))
+          keyword_args           ||= {}
+          keyword_args[matches[1]] = Expression.parse(matches[2])
+        else
+          filter_args << Expression.parse(a)
         end
-        filterargs << keyword_args unless keyword_args.empty?
-        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
+
+    def taint_check(context, obj)
+      return unless obj.tainted?
+      return if Template.taint_mode == :lax
+
+      @markup =~ QUOTED_FRAGMENT
+      name = Regexp.last_match(0)
+
+      error               = TaintedError.new("variable '#{name}' is tainted and was not escaped")
+      error.line_number   = line_number
+      error.template_name = context.template_name
+
+      case Template.taint_mode
+      when :warn
+        context.warnings << error
+      when :error
+        raise error
+      end
+    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(VARIABLE_PARSER)
+
+      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

@@ -1,4 +1,6 @@
 # encoding: utf-8
+# frozen_string_literal: true
+
 module Liquid
-  VERSION = "2.6.0"
+  VERSION = "4.0.3"
 end

liquid.gemspec

@@ -1,6 +1,8 @@
 # encoding: utf-8
+# frozen_string_literal: true
+
 lib = File.expand_path('../lib/', __FILE__)
-$:.unshift lib unless $:.include?(lib)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
 require "liquid/version"
 
@@ -9,17 +11,22 @@ Gem::Specification.new do |s|
   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 Luetke"]
+  s.authors     = ["Tobias Lütke"]
   s.email       = ["tobi@leetsoft.com"]
   s.homepage    = "http://www.liquidmarkup.org"
-  #s.description = "A secure, non-evaling end user template engine with aesthetic markup."
+  s.license     = "MIT"
+  # s.description = "A secure, non-evaling end user template engine with aesthetic markup."
 
+  s.required_ruby_version     = ">= 2.4.0"
   s.required_rubygems_version = ">= 1.3.7"
 
   s.test_files  = Dir.glob("{test}/**/*")
-  s.files       = Dir.glob("{lib}/**/*") + %w(MIT-LICENSE README.md)
+  s.files       = Dir.glob("{lib}/**/*") + %w(LICENSE README.md)
 
-  s.extra_rdoc_files  = ["History.md", "README.md"]
+  s.extra_rdoc_files = ["History.md", "README.md"]
 
   s.require_path = "lib"
+
+  s.add_development_dependency('rake', '~> 11.3')
+  s.add_development_dependency('minitest')
 end

performance/benchmark.rb

@@ -1,11 +1,20 @@
-require 'rubygems'
-require 'benchmark'
-require File.dirname(__FILE__) + '/theme_runner'
+# 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.bmbm do |x|
-  x.report("parse:")   { 100.times { profiler.compile } }
-  x.report("parse & run:")   { 100.times { profiler.run } }
-end
+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

@@ -1,19 +1,26 @@
-require 'rubygems'
-require 'ruby-prof' rescue fail("install ruby-prof extension/gem")
-require File.dirname(__FILE__) + '/theme_runner'
+# frozen_string_literal: true
 
+require 'stackprof'
+require_relative 'theme_runner'
+
+Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
 profiler = ThemeRunner.new
+profiler.run
 
-puts 'Running profiler...'
+[: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
 
-results  = profiler.run
+  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
 
-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" : "/callgrind.liquid.#{klass.name.downcase}.txt")
-  filename.gsub!(/:+/, '_')
-  File.open(filename, "w+") { |fp| klass.new(results).print(fp, :print_file => true) }
-  $stderr.puts "wrote #{klass.name} output to #{filename}"
+  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/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
+  SYNTAX = /(#{Liquid::VariableSignature}+)/
 
+  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

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

performance/shopify/money_filter.rb

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

performance/shopify/paginate.rb

@@ -1,66 +1,65 @@
+# frozen_string_literal: true
+
 class Paginate < Liquid::Block
-  Syntax     = /(#{Liquid::QuotedFragment})\s*(by\s*(\d+))?/
+  SYNTAX = /(#{Liquid::QUOTED_FRAGMENT})\s*(by\s*(\d+))?/
 
-  def initialize(tag_name, markup, tokens)
-    @nodelist = []
+  def initialize(tag_name, markup, options)
+    super
 
-    if markup =~ Syntax
-      @collection_name = $1
-      @page_size = if $2
-        $3.to_i
+    if markup =~ SYNTAX
+      @collection_name = Regexp.last_match(1)
+      @page_size       = if Regexp.last_match(2)
+        Regexp.last_match(3).to_i
       else
         20
       end
 
       @attributes = { 'window_size' => 3 }
-      markup.scan(Liquid::TagAttributes) do |key, value|
+      markup.scan(Liquid::TAG_ATTRIBUTES) do |key, value|
         @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

performance/shopify/shop_filter.rb

@@ -1,5 +1,6 @@
-module ShopFilter
+# frozen_string_literal: true
 
+module ShopFilter
   def asset_url(input)
     "/files/1/[shop_id]/[shop_id]/assets/#{input}"
   end
@@ -16,21 +17,21 @@ module ShopFilter
     %(<script src="#{url}" type="text/javascript"></script>)
   end
 
-  def stylesheet_tag(url, media="all")
+  def stylesheet_tag(url, media = "all")
     %(<link href="#{url}" rel="stylesheet" type="text/css"  media="#{media}"  />)
   end
 
-  def link_to(link, url, title="")
-    %|<a href="#{url}" title="#{title}">#{link}</a>|
+  def link_to(link, url, title = "")
+    %(<a href="#{url}" title="#{title}">#{link}</a>)
   end
 
-  def img_tag(url, alt="")
-    %|<img src="#{url}" alt="#{alt}" />|
+  def img_tag(url, alt = "")
+    %(<img src="#{url}" alt="#{alt}" />)
   end
 
   def link_to_vendor(vendor)
     if vendor
-      link_to vendor, url_for_vendor(vendor), vendor
+      link_to(vendor, url_for_vendor(vendor), vendor)
     else
       'Unknown Vendor'
     end
@@ -38,23 +39,22 @@ module ShopFilter
 
   def link_to_type(type)
     if type
-      link_to type, url_for_type(type), type
+      link_to(type, url_for_type(type), type)
     else
       'Unknown Vendor'
     end
   end
 
   def url_for_vendor(vendor_title)
-    "/collections/#{vendor_title.to_handle}"
+    "/collections/#{to_handle(vendor_title)}"
   end
 
   def url_for_type(type_title)
-    "/collections/#{type_title.to_handle}"
+    "/collections/#{to_handle(type_title)}"
   end
 
   def product_img_url(url, style = 'small')
-
-    unless url =~ /^products\/([\w\-\_]+)\.(\w{2,4})/
+    unless url =~ %r{\Aproducts/([\w\-\_]+)\.(\w{2,4})}
       raise ArgumentError, 'filter "size" can only be called on product images'
     end
 
@@ -62,27 +62,24 @@ module ShopFilter
     when 'original'
       return '/files/shops/random_number/' + url
     when 'grande', 'large', 'medium', 'compact', 'small', 'thumb', 'icon'
-      "/files/shops/random_number/products/#{$1}_#{style}.#{$2}"
+      "/files/shops/random_number/products/#{Regexp.last_match(1)}_#{style}.#{Regexp.last_match(2)}"
     else
       raise ArgumentError, 'valid parameters for filter "size" are: original, grande, large, medium, compact, small, thumb and icon '
     end
   end
 
   def default_pagination(paginate)
-
     html = []
     html << %(<span class="prev">#{link_to(paginate['previous']['title'], paginate['previous']['url'])}</span>) if paginate['previous']
 
-    for part in paginate['parts']
-
-      if part['is_link']
-        html << %(<span class="page">#{link_to(part['title'], part['url'])}</span>)
+    paginate['parts'].each do |part|
+      html << if part['is_link']
+        %(<span class="page">#{link_to(part['title'], part['url'])}</span>)
       elsif part['title'].to_i == paginate['current_page'].to_i
-        html << %(<span class="page current">#{part['title']}</span>)
+        %(<span class="page current">#{part['title']}</span>)
       else
-        html << %(<span class="deco">#{part['title']}</span>)
+        %(<span class="deco">#{part['title']}</span>)
       end
-
     end
 
     html << %(<span class="next">#{link_to(paginate['next']['title'], paginate['next']['url'])}</span>) if paginate['next']
@@ -95,4 +92,15 @@ module ShopFilter
     input == 1 ? singular : plural
   end
 
+  private
+
+  def to_handle(str)
+    result = str.dup
+    result.downcase!
+    result.delete!("'\"()[]")
+    result.gsub!(/\W+/, '-')
+    result.gsub!(/-+\z/, '') if result[-1] == '-'
+    result.gsub!(/\A-+/, '') if result[0] == '-'
+    result
+  end
 end

performance/shopify/tag_filter.rb

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

performance/shopify/weight_filter.rb

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

performance/tests/dropify/index.liquid

@@ -28,7 +28,7 @@
   {% else %}
     <div class="article-body textile">
     In <em>Admin &gt; Blogs &amp; Pages</em>, create a page with the handle <strong><code>frontpage</code></strong> and it will show up here.<br />
-    {{ "Learn more about handles" | link_to "http://wiki.shopify.com/Handle" }}
+    {{ "Learn more about handles" | link_to: "http://wiki.shopify.com/Handle" }}
     </div>
   {% endif %}
 

performance/tests/ripen/index.liquid

@@ -26,7 +26,7 @@
       {{ article.content }}
     {% else %}
       In <em>Admin &gt; Blogs &amp; Pages</em>, create a page with the handle <strong><code>frontpage</code></strong> and it will show up here.<br />
-      {{ "Learn more about handles" | link_to "http://wiki.shopify.com/Handle" }}
+      {{ "Learn more about handles" | link_to: "http://wiki.shopify.com/Handle" }}
     {% endif %}
   </div>
 </div>

performance/tests/vogue/index.liquid

@@ -5,7 +5,7 @@
       {{ article.content }}
     {% else %}
       In <em>Admin &gt; Blogs &amp; Pages</em>, create a page with the handle <strong><code>frontpage</code></strong> and it will show up here.<br />
-      {{ "Learn more about handles" | link_to "http://wiki.shopify.com/Handle" }}
+      {{ "Learn more about handles" | link_to: "http://wiki.shopify.com/Handle" }}
     {% endif %}
   </div>
 

performance/theme_runner.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This profiler run simulates Shopify.
 # We are looking in the tests directory for liquid files and render them within the designated layout file.
 # We will also export a substantial database to liquid which the templates can render values of.
@@ -6,115 +8,115 @@
 # 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_relative 'shopify/liquid'
+require_relative 'shopify/database'
 
 class ThemeRunner
   class FileSystem
-
     def initialize(path)
       @path = path
     end
 
     # Called by Liquid to retrieve a template file
-    def read_template_file(template_path, context)
+    def read_template_file(template_path)
       File.read(@path + '/' + template_path + '.liquid')
     end
   end
 
-  # Load all templates into memory, do this now so that
-  # we don't profile IO.
+  # Initialize a new liquid ThemeRunner instance
+  # Will load all templates into memory, do this now so that we don't profile IO.
   def initialize
-    @tests = Dir[File.dirname(__FILE__) + '/tests/**/*.liquid'].collect do |test|
+    @tests = Dir[__dir__ + '/tests/**/*.liquid'].collect do |test|
       next if File.basename(test) == 'theme.liquid'
 
       theme_path = File.dirname(test) + '/theme.liquid'
-
-      [File.read(test), (File.file?(theme_path) ? File.read(theme_path) : nil), test]
+      {
+        liquid: File.read(test),
+        layout: (File.file?(theme_path) ? File.read(theme_path) : nil),
+        template_name: test,
+      }
     end.compact
+
+    compile_all_tests
   end
 
+  # `compile` will test just the compilation portion of liquid without any templates
   def compile
-    # Dup assigns because will make some changes to them
-
-    @tests.each do |liquid, layout, template_name|
-
-      tmpl = Liquid::Template.new
-      tmpl.parse(liquid)
-      tmpl = Liquid::Template.new
-      tmpl.parse(layout)
+    @tests.each do |test_hash|
+      Liquid::Template.new.parse(test_hash[:liquid])
+      Liquid::Template.new.parse(test_hash[:layout])
     end
   end
 
-   def run
-    # Dup assigns because will make some changes to them
-    assigns = Database.tables.dup
-
-    @tests.each do |liquid, layout, template_name|
-
-      # Compute page_tempalte outside of profiler run, uninteresting to profiler
-      page_template = File.basename(template_name, File.extname(template_name))
+  # `run` is called to benchmark rendering and compiling at the same time
+  def run
+    each_test do |liquid, layout, assigns, page_template, template_name|
       compile_and_render(liquid, layout, assigns, page_template, template_name)
-
     end
   end
 
+  # `render` is called to benchmark just the render portion of liquid
+  def render
+    @compiled_tests.each do |test|
+      tmpl    = test[:tmpl]
+      assigns = test[:assigns]
+      layout  = test[:layout]
 
-  def run_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))
-
-      unless @started
-        RubyProf.start
-        RubyProf.pause
-        @started = true
+      if layout
+        assigns['content_for_layout'] = tmpl.render!(assigns)
+        layout.render!(assigns)
+      else
+        tmpl.render!(assigns)
       end
-
-      html = nil
-
-      RubyProf.resume
-      html = compile_and_render(liquid, layout, assigns, page_template, template_name)
-      RubyProf.pause
-
-
-      # 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
 
+  private
+
   def compile_and_render(template, layout, assigns, page_template, template_file)
-    tmpl = Liquid::Template.new
-    tmpl.assigns['page_title'] = 'Page title'
-    tmpl.assigns['template'] = page_template
-    tmpl.registers[:file_system] = ThemeRunner::FileSystem.new(File.dirname(template_file))
+    compiled_test                 = compile_test(template, layout, assigns, page_template, template_file)
+    assigns['content_for_layout'] = compiled_test[:tmpl].render!(assigns)
+    compiled_test[:layout].render!(assigns) if layout
+  end
 
-    content_for_layout = tmpl.parse(template).render(assigns)
+  def compile_all_tests
+    @compiled_tests = []
+    each_test do |liquid, layout, assigns, page_template, template_name|
+      @compiled_tests << compile_test(liquid, layout, assigns, page_template, template_name)
+    end
+    @compiled_tests
+  end
+
+  def compile_test(template, layout, assigns, page_template, template_file)
+    tmpl            = init_template(page_template, template_file)
+    parsed_template = tmpl.parse(template).dup
 
     if layout
-      assigns['content_for_layout'] = content_for_layout
-      tmpl.parse(layout).render(assigns)
+      parsed_layout = tmpl.parse(layout)
+      { tmpl: parsed_template, assigns: assigns, layout: parsed_layout }
     else
-      content_for_layout
+      { tmpl: parsed_template, assigns: assigns }
     end
   end
+
+  # utility method with similar functionality needed in `compile_all_tests` and `run`
+  def each_test
+    # Dup assigns because will make some changes to them
+    assigns = Database.tables.dup
+
+    @tests.each do |test_hash|
+      # Compute page_template outside of profiler run, uninteresting to profiler
+      page_template = File.basename(test_hash[:template_name], File.extname(test_hash[:template_name]))
+      yield(test_hash[:liquid], test_hash[:layout], assigns, page_template, test_hash[:template_name])
+    end
+  end
+
+  # set up a new Liquid::Template object for use in `compile_and_render` and `compile_test`
+  def init_template(page_template, template_file)
+    tmpl                         = Liquid::Template.new
+    tmpl.assigns['page_title']   = 'Page title'
+    tmpl.assigns['template']     = page_template
+    tmpl.registers[:file_system] = ThemeRunner::FileSystem.new(File.dirname(template_file))
+    tmpl
+  end
 end
-
-
-

test/fixtures/en_locale.yml

@@ -0,0 +1,9 @@
+---
+  simple: "less is more"
+  whatever: "something %{something}"
+  errors:
+    i18n:
+      undefined_interpolation: "undefined key %{key}"
+      unknown_translation: "translation '%{name}' wasn't found"
+    syntax:
+      oops: "something wasn't right"

test/integration/assign_test.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class AssignTest < Minitest::Test
+  include Liquid
+
+  def test_assign_with_hyphen_in_variable_name
+    template_source = <<-END_TEMPLATE
+    {% assign this-thing = 'Print this-thing' %}
+    {{ this-thing }}
+    END_TEMPLATE
+    template        = Template.parse(template_source)
+    rendered        = template.render!
+    assert_equal("Print this-thing", rendered.strip)
+  end
+
+  def test_assigned_variable
+    assert_template_result('.foo.',
+      '{% assign foo = values %}.{{ foo[0] }}.',
+      'values' => %w(foo bar baz))
+
+    assert_template_result('.bar.',
+      '{% assign foo = values %}.{{ foo[1] }}.',
+      'values' => %w(foo bar baz))
+  end
+
+  def test_assign_with_filter
+    assert_template_result('.bar.',
+      '{% assign foo = values | split: "," %}.{{ foo[1] }}.',
+      'values' => "foo,bar,baz")
+  end
+
+  def test_assign_syntax_error
+    assert_match_syntax_error(/assign/,
+      '{% assign foo not values %}.',
+      'values' => "foo,bar,baz")
+  end
+
+  def test_assign_uses_error_mode
+    with_error_mode(:strict) do
+      assert_raises(SyntaxError) do
+        Template.parse("{% assign foo = ('X' | downcase) %}")
+      end
+    end
+    with_error_mode(:lax) do
+      assert Template.parse("{% assign foo = ('X' | downcase) %}")
+    end
+  end
+end # AssignTest

test/integration/blank_test.rb

@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class FoobarTag < Liquid::Tag
+  def render_to_output_buffer(_context, output)
+    output << ' '
+    output
+  end
+end
+
+class BlankTestFileSystem
+  def read_template_file(template_path)
+    template_path
+  end
+end
+
+class BlankTest < Minitest::Test
+  include Liquid
+  N = 10
+
+  def wrap_in_for(body)
+    "{% for i in (1..#{N}) %}#{body}{% endfor %}"
+  end
+
+  def wrap_in_if(body)
+    "{% if true %}#{body}{% endif %}"
+  end
+
+  def wrap(body)
+    wrap_in_for(body) + wrap_in_if(body)
+  end
+
+  def test_new_tags_are_not_blank_by_default
+    with_custom_tag('foobar', FoobarTag) do
+      assert_template_result(" " * N, wrap_in_for("{% foobar %}"))
+    end
+  end
+
+  def test_loops_are_blank
+    assert_template_result("", wrap_in_for(" "))
+  end
+
+  def test_if_else_are_blank
+    assert_template_result("", "{% if true %} {% elsif false %} {% else %} {% endif %}")
+  end
+
+  def test_unless_is_blank
+    assert_template_result("", wrap("{% unless true %} {% endunless %}"))
+  end
+
+  def test_mark_as_blank_only_during_parsing
+    assert_template_result(" " * (N + 1), wrap(" {% if false %} this never happens, but still, this block is not blank {% endif %}"))
+  end
+
+  def test_comments_are_blank
+    assert_template_result("", wrap(" {% comment %} whatever {% endcomment %} "))
+  end
+
+  def test_captures_are_blank
+    assert_template_result("", wrap(" {% capture foo %} whatever {% endcapture %} "))
+  end
+
+  def test_nested_blocks_are_blank_but_only_if_all_children_are
+    assert_template_result("", wrap(wrap(" ")))
+    assert_template_result("\n       but this is not " * (N + 1),
+      wrap('{% if true %} {% comment %} this is blank {% endcomment %} {% endif %}
+      {% if true %} but this is not {% endif %}'))
+  end
+
+  def test_assigns_are_blank
+    assert_template_result("", wrap(' {% assign foo = "bar" %} '))
+  end
+
+  def test_whitespace_is_blank
+    assert_template_result("", wrap(" "))
+    assert_template_result("", wrap("\t"))
+  end
+
+  def test_whitespace_is_not_blank_if_other_stuff_is_present
+    body = "     x "
+    assert_template_result(body * (N + 1), wrap(body))
+  end
+
+  def test_increment_is_not_blank
+    assert_template_result(" 0" * 2 * (N + 1), wrap("{% assign foo = 0 %} {% increment foo %} {% decrement foo %}"))
+  end
+
+  def test_cycle_is_not_blank
+    assert_template_result("  " * ((N + 1) / 2) + " ", wrap("{% cycle ' ', ' ' %}"))
+  end
+
+  def test_raw_is_not_blank
+    assert_template_result("  " * (N + 1), wrap(" {% raw %} {% endraw %}"))
+  end
+
+  def test_include_is_blank
+    Liquid::Template.file_system = BlankTestFileSystem.new
+    assert_template_result("foobar" * (N + 1), wrap("{% include 'foobar' %}"))
+    assert_template_result(" foobar " * (N + 1), wrap("{% include ' foobar ' %}"))
+    assert_template_result("   " * (N + 1), wrap(" {% include ' ' %} "))
+  end
+
+  def test_case_is_blank
+    assert_template_result("", wrap(" {% assign foo = 'bar' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} {% endcase %} "))
+    assert_template_result("", wrap(" {% assign foo = 'else' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} {% endcase %} "))
+    assert_template_result("   x  " * (N + 1), wrap(" {% assign foo = 'else' %} {% case foo %} {% when 'bar' %} {% when 'whatever' %} {% else %} x {% endcase %} "))
+  end
+end

test/integration/block_test.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class BlockTest < Minitest::Test
+  include Liquid
+
+  def test_unexpected_end_tag
+    exc = assert_raises(SyntaxError) do
+      Template.parse("{% if true %}{% endunless %}")
+    end
+    assert_equal(exc.message, "Liquid syntax error: 'endunless' is not a valid delimiter for if tags. use endif")
+  end
+end