WIP3

History.md

@@ -1,5 +1,55 @@
 # Liquid Change Log
 
+## 6.0.0
+
+### Features
+* Add support for boolean expressions everywhere
+  * As variable output `{{ a or b }}`
+  * As filter argument `{{ collection | where: 'prop', a or b }}`
+  * As tag argument `{% render 'snip', enabled: a or b %}`
+  * As conditional tag argument `{% if cond %}` (extending previous behaviour)
+* Add support for subexpression prioritization and associativity
+  * In ascending order of priority:
+    * Logical: `and`, `or` (right to left)
+    * Equality: `==`, `!=`, `<>` (left to right)
+    * Comparison: `>`, `>=`, `<`, `<=`, `contains` (left to right)
+    * Groupings: `( expr )`
+  - For example, this is now supported
+    * `{{ a > b == c < d or e == f }}` which is equivalent to
+    * `{{ ((a > b) == (c < d)) or (e == f) }}`
+- Add support for parenthesized expressions
+  * e.g. `(a or b) == c`
+
+### Architectural changes
+* `parse_expression` and `safe_parse_expression` have been removed from `Tag` and `ParseContext`
+* `Parser` methods now produce AST nodes instead of strings
+  * `Parser#expression` produces a value,
+  * `Parser#string` produces a string,
+  * etc.
+
+### Breaking changes
+* The Environment's `error_mode` option has been removed.
+  * `:warn` is no longer supported
+  * `:lax` and `lax_parse` is no longer supported
+  * `:strict` and `strict_parse` is no longer supported
+  * `strict2_parse` is renamed to `parse_markup`
+* Expressions
+  * The `warnings` system has been removed.
+  * `Parser#expression` is renamed to `Parser#expression_string`
+  * `safe_parse_expression` methods are replaced by `Parser#expression`
+  * `parse_expression` methods are replaced by `Parser#unsafe_parse_expression`
+* `Condition`
+  * `new(expr)` no longer accepts an `op` or `right`. Logic moved to BinaryExpression.
+  * `Condition#or` and `Condition#and` were replaced by `BinaryExpression`.
+  * `Condition#child_relation` replaced by `BinaryExpression`.
+  * `Condition.operations` was removed.
+  * `Condtion::MethodLiteral` was moved to the `Liquid` namespace
+
+### Migrating from `^5.11.0`
+- In custom tags that include `ParserSwitching`, rename `strict2_parse` to `parse_markup`
+- Remove code depending on `:error_mode`
+- Replace `safe_parse_expression` calls with `Parser#expression`
+
 ## 5.11.0
 * Revert the Inline Snippets tag (#2001), treat its inclusion in the latest Liquid release as a bug, and allow for feedback on RFC#1916 to better support Liquid developers [Guilherme Carreiro]
 * Rename the `:rigid` error mode to `:strict2` and display a warning when users attempt to use the `:rigid` mode [Guilherme Carreiro]

README.md

@@ -93,31 +93,6 @@ LIQUID
 
 By using Environments, you ensure that custom tags and filters are only available in the contexts where they are needed, making your Liquid templates more robust and easier to manage. For smaller projects, a global environment is available via `Liquid::Environment.default`.
 
-### 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 different parsers 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::Environment.default.error_mode = :strict2 # Raises a SyntaxError when invalid syntax is used in all tags
-Liquid::Environment.default.error_mode = :strict  # Raises a SyntaxError when invalid syntax is used in some tags
-Liquid::Environment.default.error_mode = :warn    # Adds strict errors to template.errors but continues as normal
-Liquid::Environment.default.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.

Rakefile

@@ -33,29 +33,12 @@ task :rubocop do
   end
 end
 
-desc('runs test suite with lax, strict, and strict2 parsers')
+desc('runs test suite')
 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
-
-  ENV['LIQUID_PARSER_MODE'] = 'strict2'
   Rake::Task['base_test'].reenable
   Rake::Task['base_test'].invoke
 
   if RUBY_ENGINE == 'ruby' || RUBY_ENGINE == 'truffleruby'
-    ENV['LIQUID_PARSER_MODE'] = 'lax'
-    Rake::Task['integration_test'].reenable
-    Rake::Task['integration_test'].invoke
-
-    ENV['LIQUID_PARSER_MODE'] = 'strict'
-    Rake::Task['integration_test'].reenable
-    Rake::Task['integration_test'].invoke
-
-    ENV['LIQUID_PARSER_MODE'] = 'strict2'
     Rake::Task['integration_test'].reenable
     Rake::Task['integration_test'].invoke
   end
@@ -78,24 +61,11 @@ task release: :build do
 end
 
 namespace :benchmark do
-  desc "Run the liquid benchmark with lax parsing"
-  task :lax do
-    ruby "./performance/benchmark.rb lax"
-  end
-
-  desc "Run the liquid benchmark with strict parsing"
-  task :strict do
-    ruby "./performance/benchmark.rb strict"
-  end
-
-  desc "Run the liquid benchmark with strict2 parsing"
-  task :strict2 do
-    ruby "./performance/benchmark.rb strict2"
+  desc "Run the liquid benchmark"
+  task :run do
+    ruby "./performance/benchmark.rb"
   end
 
-  desc "Run the liquid benchmark with lax, strict, and strict2 parsing"
-  task run: [:lax, :strict, :strict2]
-
   desc "Run unit benchmarks"
   namespace :unit do
     task :all do
@@ -126,11 +96,6 @@ namespace :profile do
   task :run do
     ruby "./performance/profile.rb"
   end
-
-  desc "Run the liquid profile/performance coverage with strict parsing"
-  task :strict do
-    ruby "./performance/profile.rb strict"
-  end
 end
 
 namespace :memory_profile do

lib/liquid.rb

@@ -62,6 +62,8 @@ module Liquid
 require 'liquid/tags'
 require "liquid/environment"
 require 'liquid/lexer'
+require 'liquid/method_literal'
+require 'liquid/binary_expression'
 require 'liquid/parser'
 require 'liquid/i18n'
 require 'liquid/drop'

lib/liquid/binary_expression.rb

@@ -0,0 +1,94 @@
+# frozen_string_literal: true
+
+module Liquid
+  class BinaryExpression
+    attr_reader :operator
+    attr_accessor :left_node, :right_node
+
+    def initialize(left, operator, right)
+      @left_node = left
+      @operator = operator
+      @right_node = right
+    end
+
+    def evaluate(context)
+      left = value(left_node, context)
+
+      # logical relation short circuiting
+      if operator == 'and'
+        return left && value(right_node, context)
+      elsif operator == 'or'
+        return left || value(right_node, context)
+      end
+
+      right = value(right_node, context)
+
+      case operator
+      when '>'
+        left > right if can_compare?(left, right)
+      when '>='
+        left >= right if can_compare?(left, right)
+      when '<'
+        left < right if can_compare?(left, right)
+      when '<='
+        left <= right if can_compare?(left, right)
+      when '=='
+        equal_variables(left, right)
+      when '!=', '<>'
+        !equal_variables(left, right)
+      when 'contains'
+        contains(left, right)
+      else
+        raise(Liquid::ArgumentError, "Unknown operator #{operator}")
+      end
+    rescue ::ArgumentError => e
+      raise Liquid::ArgumentError, e.message
+    end
+
+    def to_s
+      "(#{left_node.inspect} #{operator} #{right_node.inspect})"
+    end
+
+    private
+
+    def value(expr, context)
+      Utils.to_liquid_value(context.evaluate(expr))
+    end
+
+    def can_compare?(left, right)
+      left.respond_to?(operator) && right.respond_to?(operator) && !left.is_a?(Hash) && !right.is_a?(Hash)
+    end
+
+    def contains(left, right)
+      if left && right && left.respond_to?(:include?)
+        right = right.to_s if left.is_a?(String)
+        left.include?(right)
+      else
+        false
+      end
+    rescue Encoding::CompatibilityError
+      # "✅".b.include?("✅") raises Encoding::CompatibilityError despite being materially equal
+      left.b.include?(right.b)
+    end
+
+    def apply_method_literal(node, other)
+      other.send(node.method_name) if other.respond_to?(node.method_name)
+    end
+
+    def equal_variables(left, right)
+      return apply_method_literal(left, right) if left.is_a?(MethodLiteral)
+      return apply_method_literal(right, left) if right.is_a?(MethodLiteral)
+
+      left == right
+    end
+
+    class ParseTreeVisitor < Liquid::ParseTreeVisitor
+      def children
+        [
+          @node.left_node,
+          @node.right_node,
+        ]
+      end
+    end
+  end
+end