From fe66edb8254a4af4af3a69a32884178e2263c421 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Fri, 23 Oct 2020 10:53:16 -0400
Subject: [PATCH 1/9] Freeze block body after parsing completes

---
 Gemfile                  | 2 +-
 lib/liquid/block.rb      | 1 +
 lib/liquid/block_body.rb | 9 +++++++++
 lib/liquid/document.rb   | 1 +
 lib/liquid/tags/case.rb  | 6 +++++-
 lib/liquid/tags/for.rb   | 2 ++
 lib/liquid/tags/if.rb    | 1 +
 7 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/Gemfile b/Gemfile
index 14537c6..338fe56 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,6 +22,6 @@ group :test do
   gem 'rubocop-performance', require: false
 
   platform :mri, :truffleruby do
-    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'master'
+    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'pz-block-body-buffer'
   end
 end
diff --git a/lib/liquid/block.rb b/lib/liquid/block.rb
index 47d5f25..d6619f9 100644
--- a/lib/liquid/block.rb
+++ b/lib/liquid/block.rb
@@ -13,6 +13,7 @@ module Liquid
       @body = new_body
       while parse_body(@body, tokens)
       end
+      @body.freeze(parse_context)
     end
 
     # For backwards compatibility
diff --git a/lib/liquid/block_body.rb b/lib/liquid/block_body.rb
index 67d5d63..f61ae87 100644
--- a/lib/liquid/block_body.rb
+++ b/lib/liquid/block_body.rb
@@ -16,9 +16,12 @@ module Liquid
     def initialize
       @nodelist = []
       @blank    = true
+      @frozen   = false
     end
 
     def parse(tokenizer, parse_context, &block)
+      raise FrozenError, "can't modify frozen Liquid::BlockBody" if @frozen
+
       parse_context.line_number = tokenizer.line_number
 
       if tokenizer.for_liquid_tag
@@ -28,6 +31,10 @@ module Liquid
       end
     end
 
+    def freeze(_context)
+      @frozen = true
+    end
+
     private def parse_for_liquid_tag(tokenizer, parse_context)
       while (token = tokenizer.shift)
         unless token.empty? || token =~ WhitespaceOrNothing
@@ -192,6 +199,8 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
+      raise "Can only render when frozen" unless @frozen
+
       context.resource_limits.increment_render_score(@nodelist.length)
 
       idx = 0
diff --git a/lib/liquid/document.rb b/lib/liquid/document.rb
index 2e47ffb..21ddec2 100644
--- a/lib/liquid/document.rb
+++ b/lib/liquid/document.rb
@@ -22,6 +22,7 @@ module Liquid
     def parse(tokenizer, parse_context)
       while parse_body(tokenizer)
       end
+      @body.freeze(parse_context)
     rescue SyntaxError => e
       e.line_number ||= parse_context.line_number
       raise
diff --git a/lib/liquid/tags/case.rb b/lib/liquid/tags/case.rb
index b46fa05..cc85ed4 100644
--- a/lib/liquid/tags/case.rb
+++ b/lib/liquid/tags/case.rb
@@ -20,7 +20,11 @@ module Liquid
 
     def parse(tokens)
       body = new_body
-      body = @blocks.last.attachment while parse_body(body, tokens)
+      while parse_body(body, tokens)
+        body.freeze(parse_context)
+        body = @blocks.last.attachment
+      end
+      body.freeze(parse_context)
       if blank?
         @blocks.each { |condition| condition.attachment.remove_blank_strings }
       end
diff --git a/lib/liquid/tags/for.rb b/lib/liquid/tags/for.rb
index 6f66ebd..9a81b4d 100644
--- a/lib/liquid/tags/for.rb
+++ b/lib/liquid/tags/for.rb
@@ -61,7 +61,9 @@ module Liquid
     def parse(tokens)
       if parse_body(@for_block, tokens)
         parse_body(@else_block, tokens)
+        @else_block.freeze(parse_context)
       end
+      @for_block.freeze(parse_context)
       if blank?
         @for_block.remove_blank_strings
         @else_block&.remove_blank_strings
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index c910b0b..7632be9 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -31,6 +31,7 @@ module Liquid
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
+      @blocks.each { |block| block.attachment.freeze(parse_context) }
       if blank?
         @blocks.each { |condition| condition.attachment.remove_blank_strings }
       end

From 0bedc71854196ebb0164a6eaccc93f8c8e889aa3 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Mon, 26 Oct 2020 15:11:00 -0400
Subject: [PATCH 2/9] Address comments

---
 Gemfile                  |  2 +-
 lib/liquid/block.rb      | 20 +++++++++++++++-----
 lib/liquid/block_body.rb | 10 +++++-----
 lib/liquid/document.rb   |  2 +-
 lib/liquid/tags/case.rb  |  9 +--------
 lib/liquid/tags/for.rb   |  6 ------
 lib/liquid/tags/if.rb    |  4 ----
 7 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/Gemfile b/Gemfile
index 338fe56..14537c6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,6 +22,6 @@ group :test do
   gem 'rubocop-performance', require: false
 
   platform :mri, :truffleruby do
-    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'pz-block-body-buffer'
+    gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'master'
   end
 end
diff --git a/lib/liquid/block.rb b/lib/liquid/block.rb
index d6619f9..4299915 100644
--- a/lib/liquid/block.rb
+++ b/lib/liquid/block.rb
@@ -11,9 +11,9 @@ module Liquid
 
     def parse(tokens)
       @body = new_body
-      while parse_body(@body, tokens)
+      while parse_body(@body, tokens, partial: true)
       end
-      @body.freeze(parse_context)
+      @body.freeze
     end
 
     # For backwards compatibility
@@ -68,7 +68,9 @@ module Liquid
     end
 
     # @api public
-    def parse_body(body, tokens)
+    def parse_body(body, tokens, partial: false)
+      block_terminated = true
+
       if parse_context.depth >= MAX_DEPTH
         raise StackLevelError, "Nesting too deep"
       end
@@ -77,7 +79,10 @@ module Liquid
         body.parse(tokens, parse_context) do |end_tag_name, end_tag_params|
           @blank &&= body.blank?
 
-          return false if end_tag_name == block_delimiter
+          if end_tag_name == block_delimiter
+            block_terminated = false
+            next
+          end
           raise_tag_never_closed(block_name) unless end_tag_name
 
           # this tag is not registered with the system
@@ -88,7 +93,12 @@ module Liquid
         parse_context.depth -= 1
       end
 
-      true
+      unless partial
+        body.remove_blank_strings if body.blank?
+        body.freeze
+      end
+
+      block_terminated
     end
   end
 end
diff --git a/lib/liquid/block_body.rb b/lib/liquid/block_body.rb
index f61ae87..b8350a3 100644
--- a/lib/liquid/block_body.rb
+++ b/lib/liquid/block_body.rb
@@ -16,11 +16,10 @@ module Liquid
     def initialize
       @nodelist = []
       @blank    = true
-      @frozen   = false
     end
 
     def parse(tokenizer, parse_context, &block)
-      raise FrozenError, "can't modify frozen Liquid::BlockBody" if @frozen
+      raise FrozenError, "can't modify frozen Liquid::BlockBody" if frozen?
 
       parse_context.line_number = tokenizer.line_number
 
@@ -31,8 +30,9 @@ module Liquid
       end
     end
 
-    def freeze(_context)
-      @frozen = true
+    def freeze
+      @nodelist.freeze
+      super
     end
 
     private def parse_for_liquid_tag(tokenizer, parse_context)
@@ -199,7 +199,7 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
-      raise "Can only render when frozen" unless @frozen
+      raise "Can only render when frozen" unless frozen?
 
       context.resource_limits.increment_render_score(@nodelist.length)
 
diff --git a/lib/liquid/document.rb b/lib/liquid/document.rb
index 21ddec2..9bf13b4 100644
--- a/lib/liquid/document.rb
+++ b/lib/liquid/document.rb
@@ -22,7 +22,7 @@ module Liquid
     def parse(tokenizer, parse_context)
       while parse_body(tokenizer)
       end
-      @body.freeze(parse_context)
+      @body.freeze
     rescue SyntaxError => e
       e.line_number ||= parse_context.line_number
       raise
diff --git a/lib/liquid/tags/case.rb b/lib/liquid/tags/case.rb
index cc85ed4..734f166 100644
--- a/lib/liquid/tags/case.rb
+++ b/lib/liquid/tags/case.rb
@@ -20,14 +20,7 @@ module Liquid
 
     def parse(tokens)
       body = new_body
-      while parse_body(body, tokens)
-        body.freeze(parse_context)
-        body = @blocks.last.attachment
-      end
-      body.freeze(parse_context)
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
-      end
+      body = @blocks.last.attachment while parse_body(body, tokens)
     end
 
     def nodelist
diff --git a/lib/liquid/tags/for.rb b/lib/liquid/tags/for.rb
index 9a81b4d..d7e93bb 100644
--- a/lib/liquid/tags/for.rb
+++ b/lib/liquid/tags/for.rb
@@ -61,12 +61,6 @@ module Liquid
     def parse(tokens)
       if parse_body(@for_block, tokens)
         parse_body(@else_block, tokens)
-        @else_block.freeze(parse_context)
-      end
-      @for_block.freeze(parse_context)
-      if blank?
-        @for_block.remove_blank_strings
-        @else_block&.remove_blank_strings
       end
     end
 
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index 7632be9..c3b8915 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -31,10 +31,6 @@ module Liquid
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
-      @blocks.each { |block| block.attachment.freeze(parse_context) }
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
-      end
     end
 
     def unknown_tag(tag, markup, tokens)

From 5c082472a10a7795fa188dfd01b0a2763fea006d Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Mon, 26 Oct 2020 16:07:43 -0400
Subject: [PATCH 3/9] Address comments

---
 lib/liquid/block.rb      | 18 ++++--------------
 lib/liquid/block_body.rb |  2 +-
 lib/liquid/tags/case.rb  |  4 ++++
 lib/liquid/tags/for.rb   |  6 ++++++
 lib/liquid/tags/if.rb    |  4 ++++
 5 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/lib/liquid/block.rb b/lib/liquid/block.rb
index 4299915..dc22a47 100644
--- a/lib/liquid/block.rb
+++ b/lib/liquid/block.rb
@@ -11,7 +11,7 @@ module Liquid
 
     def parse(tokens)
       @body = new_body
-      while parse_body(@body, tokens, partial: true)
+      while parse_body(@body, tokens)
       end
       @body.freeze
     end
@@ -68,9 +68,7 @@ module Liquid
     end
 
     # @api public
-    def parse_body(body, tokens, partial: false)
-      block_terminated = true
-
+    def parse_body(body, tokens)
       if parse_context.depth >= MAX_DEPTH
         raise StackLevelError, "Nesting too deep"
       end
@@ -79,10 +77,7 @@ module Liquid
         body.parse(tokens, parse_context) do |end_tag_name, end_tag_params|
           @blank &&= body.blank?
 
-          if end_tag_name == block_delimiter
-            block_terminated = false
-            next
-          end
+          return false if end_tag_name == block_delimiter
           raise_tag_never_closed(block_name) unless end_tag_name
 
           # this tag is not registered with the system
@@ -93,12 +88,7 @@ module Liquid
         parse_context.depth -= 1
       end
 
-      unless partial
-        body.remove_blank_strings if body.blank?
-        body.freeze
-      end
-
-      block_terminated
+      true
     end
   end
 end
diff --git a/lib/liquid/block_body.rb b/lib/liquid/block_body.rb
index b8350a3..af62a14 100644
--- a/lib/liquid/block_body.rb
+++ b/lib/liquid/block_body.rb
@@ -199,7 +199,7 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
-      raise "Can only render when frozen" unless frozen?
+      freeze unless frozen?
 
       context.resource_limits.increment_render_score(@nodelist.length)
 
diff --git a/lib/liquid/tags/case.rb b/lib/liquid/tags/case.rb
index 734f166..caa6fff 100644
--- a/lib/liquid/tags/case.rb
+++ b/lib/liquid/tags/case.rb
@@ -21,6 +21,10 @@ module Liquid
     def parse(tokens)
       body = new_body
       body = @blocks.last.attachment while parse_body(body, tokens)
+      if blank?
+        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      end
+      @blocks.each { |condition| condition.attachment.freeze }
     end
 
     def nodelist
diff --git a/lib/liquid/tags/for.rb b/lib/liquid/tags/for.rb
index d7e93bb..df2d4db 100644
--- a/lib/liquid/tags/for.rb
+++ b/lib/liquid/tags/for.rb
@@ -62,6 +62,12 @@ module Liquid
       if parse_body(@for_block, tokens)
         parse_body(@else_block, tokens)
       end
+      if blank?
+        @for_block.remove_blank_strings
+        @else_block&.remove_blank_strings
+      end
+      @for_block.freeze
+      @else_block&.freeze
     end
 
     def nodelist
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index c3b8915..7bef1af 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -31,6 +31,10 @@ module Liquid
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
+      if blank?
+        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      end
+      @blocks.each { |block| block.attachment.freeze }
     end
 
     def unknown_tag(tag, markup, tokens)

From 292d971937e418283d68788502ad09acfd799f6d Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Tue, 27 Oct 2020 10:42:30 -0400
Subject: [PATCH 4/9] Merge loops

---
 lib/liquid/tags/case.rb | 6 +++---
 lib/liquid/tags/if.rb   | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/liquid/tags/case.rb b/lib/liquid/tags/case.rb
index caa6fff..12d1712 100644
--- a/lib/liquid/tags/case.rb
+++ b/lib/liquid/tags/case.rb
@@ -21,10 +21,10 @@ module Liquid
     def parse(tokens)
       body = new_body
       body = @blocks.last.attachment while parse_body(body, tokens)
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      @blocks.each do |condition|
+        condition.attachment.remove_blank_strings if blank?
+        condition.attachment.freeze
       end
-      @blocks.each { |condition| condition.attachment.freeze }
     end
 
     def nodelist
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index 7bef1af..d4de9c2 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -31,10 +31,10 @@ module Liquid
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      @blocks.each do |block|
+        block.attachment.remove_blank_strings if blank?
+        block.attachment.freeze
       end
-      @blocks.each { |block| block.attachment.freeze }
     end
 
     def unknown_tag(tag, markup, tokens)

From 10ea6144e0b083e894924e18a5a2319b085fd231 Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <dylan.smith@shopify.com>
Date: Tue, 27 Oct 2020 11:00:04 -0400
Subject: [PATCH 5/9] Add Liquid::ParseContext#parse_expression for liquid-c
 node disabling (#1333)

We would like to be able to disable liquid-c VM rendering at runtime,
but right now expression parsing is done using Expression.parse, which
isn't aware of the parse context.  That prevents us from conditionally
compiling to VM code based on a parse option.
---
 lib/liquid/condition.rb      | 4 ++--
 lib/liquid/parse_context.rb  | 4 ++++
 lib/liquid/tag.rb            | 6 ++++++
 lib/liquid/tags/case.rb      | 4 ++--
 lib/liquid/tags/cycle.rb     | 4 ++--
 lib/liquid/tags/for.rb       | 8 ++++----
 lib/liquid/tags/if.rb        | 2 +-
 lib/liquid/tags/include.rb   | 6 +++---
 lib/liquid/tags/render.rb    | 6 +++---
 lib/liquid/tags/table_row.rb | 4 ++--
 10 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/lib/liquid/condition.rb b/lib/liquid/condition.rb
index 56900c7..8b7dd65 100644
--- a/lib/liquid/condition.rb
+++ b/lib/liquid/condition.rb
@@ -45,8 +45,8 @@ module Liquid
       @@operators
     end
 
-    def self.parse_expression(markup)
-      @@method_literals[markup] || Expression.parse(markup)
+    def self.parse_expression(parse_context, markup)
+      @@method_literals[markup] || parse_context.parse_expression(markup)
     end
 
     attr_reader :attachment, :child_condition
diff --git a/lib/liquid/parse_context.rb b/lib/liquid/parse_context.rb
index 4724ec2..f8fb9b0 100644
--- a/lib/liquid/parse_context.rb
+++ b/lib/liquid/parse_context.rb
@@ -23,6 +23,10 @@ module Liquid
       Liquid::BlockBody.new
     end
 
+    def parse_expression(markup)
+      Expression.parse(markup)
+    end
+
     def partial=(value)
       @partial = value
       @options = value ? partial_options : @template_options
diff --git a/lib/liquid/tag.rb b/lib/liquid/tag.rb
index bd77335..085c0ef 100644
--- a/lib/liquid/tag.rb
+++ b/lib/liquid/tag.rb
@@ -55,5 +55,11 @@ module Liquid
     def blank?
       false
     end
+
+    private
+
+    def parse_expression(markup)
+      parse_context.parse_expression(markup)
+    end
   end
 end
diff --git a/lib/liquid/tags/case.rb b/lib/liquid/tags/case.rb
index b46fa05..5dc3cb3 100644
--- a/lib/liquid/tags/case.rb
+++ b/lib/liquid/tags/case.rb
@@ -12,7 +12,7 @@ module Liquid
       @blocks = []
 
       if markup =~ Syntax
-        @left = Expression.parse(Regexp.last_match(1))
+        @left = parse_expression(Regexp.last_match(1))
       else
         raise SyntaxError, options[:locale].t("errors.syntax.case")
       end
@@ -68,7 +68,7 @@ module Liquid
 
         markup = Regexp.last_match(2)
 
-        block = Condition.new(@left, '==', Condition.parse_expression(Regexp.last_match(1)))
+        block = Condition.new(@left, '==', Condition.parse_expression(parse_context, Regexp.last_match(1)))
         block.attach(body)
         @blocks << block
       end
diff --git a/lib/liquid/tags/cycle.rb b/lib/liquid/tags/cycle.rb
index 6aee14c..96f0d57 100644
--- a/lib/liquid/tags/cycle.rb
+++ b/lib/liquid/tags/cycle.rb
@@ -24,7 +24,7 @@ module Liquid
       case markup
       when NamedSyntax
         @variables = variables_from_string(Regexp.last_match(2))
-        @name      = Expression.parse(Regexp.last_match(1))
+        @name      = parse_expression(Regexp.last_match(1))
       when SimpleSyntax
         @variables = variables_from_string(markup)
         @name      = @variables.to_s
@@ -61,7 +61,7 @@ module Liquid
     def variables_from_string(markup)
       markup.split(',').collect do |var|
         var =~ /\s*(#{QuotedFragment})\s*/o
-        Regexp.last_match(1) ? Expression.parse(Regexp.last_match(1)) : nil
+        Regexp.last_match(1) ? parse_expression(Regexp.last_match(1)) : nil
       end.compact
     end
 
diff --git a/lib/liquid/tags/for.rb b/lib/liquid/tags/for.rb
index 6f66ebd..d92fa68 100644
--- a/lib/liquid/tags/for.rb
+++ b/lib/liquid/tags/for.rb
@@ -97,7 +97,7 @@ module Liquid
         collection_name  = Regexp.last_match(2)
         @reversed        = !!Regexp.last_match(3)
         @name            = "#{@variable_name}-#{collection_name}"
-        @collection_name = Expression.parse(collection_name)
+        @collection_name = parse_expression(collection_name)
         markup.scan(TagAttributes) do |key, value|
           set_attribute(key, value)
         end
@@ -112,7 +112,7 @@ module Liquid
       raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_in") unless p.id?('in')
 
       collection_name  = p.expression
-      @collection_name = Expression.parse(collection_name)
+      @collection_name = parse_expression(collection_name)
 
       @name     = "#{@variable_name}-#{collection_name}"
       @reversed = p.id?('reversed')
@@ -198,10 +198,10 @@ module Liquid
         @from = if expr == 'continue'
           :continue
         else
-          Expression.parse(expr)
+          parse_expression(expr)
         end
       when 'limit'
-        @limit = Expression.parse(expr)
+        @limit = parse_expression(expr)
       end
     end
 
diff --git a/lib/liquid/tags/if.rb b/lib/liquid/tags/if.rb
index aa437b1..90692fd 100644
--- a/lib/liquid/tags/if.rb
+++ b/lib/liquid/tags/if.rb
@@ -71,7 +71,7 @@ module Liquid
     end
 
     def parse_expression(markup)
-      Condition.parse_expression(markup)
+      Condition.parse_expression(parse_context, markup)
     end
 
     def lax_parse(markup)
diff --git a/lib/liquid/tags/include.rb b/lib/liquid/tags/include.rb
index f697e51..1a31544 100644
--- a/lib/liquid/tags/include.rb
+++ b/lib/liquid/tags/include.rb
@@ -32,12 +32,12 @@ module Liquid
         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)
+        @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
+        @template_name_expr = parse_expression(template_name)
         @attributes         = {}
 
         markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = Expression.parse(value)
+          @attributes[key] = parse_expression(value)
         end
 
       else
diff --git a/lib/liquid/tags/render.rb b/lib/liquid/tags/render.rb
index 8ce560a..6380249 100644
--- a/lib/liquid/tags/render.rb
+++ b/lib/liquid/tags/render.rb
@@ -19,13 +19,13 @@ module Liquid
       variable_name = Regexp.last_match(4)
 
       @alias_name = Regexp.last_match(6)
-      @variable_name_expr = variable_name ? Expression.parse(variable_name) : nil
-      @template_name_expr = Expression.parse(template_name)
+      @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
+      @template_name_expr = parse_expression(template_name)
       @for = (with_or_for == FOR)
 
       @attributes = {}
       markup.scan(TagAttributes) do |key, value|
-        @attributes[key] = Expression.parse(value)
+        @attributes[key] = parse_expression(value)
       end
     end
 
diff --git a/lib/liquid/tags/table_row.rb b/lib/liquid/tags/table_row.rb
index 353f9e3..eda0bc4 100644
--- a/lib/liquid/tags/table_row.rb
+++ b/lib/liquid/tags/table_row.rb
@@ -10,10 +10,10 @@ module Liquid
       super
       if markup =~ Syntax
         @variable_name   = Regexp.last_match(1)
-        @collection_name = Expression.parse(Regexp.last_match(2))
+        @collection_name = parse_expression(Regexp.last_match(2))
         @attributes      = {}
         markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = Expression.parse(value)
+          @attributes[key] = parse_expression(value)
         end
       else
         raise SyntaxError, options[:locale].t("errors.syntax.table_row")

From f23c2a83f25bf2c9755bfd7d2402f9ee3c95516f Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <dylan.smith@shopify.com>
Date: Tue, 27 Oct 2020 14:53:57 -0400
Subject: [PATCH 6/9] Fix lax parsing expressions surrounded by spaces (#1335)

to make it compatible with strict parsing and liquid-c
---
 lib/liquid/expression.rb            | 35 ++++++++++++----------
 test/integration/expression_test.rb | 46 +++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 16 deletions(-)
 create mode 100644 test/integration/expression_test.rb

diff --git a/lib/liquid/expression.rb b/lib/liquid/expression.rb
index fdbe382..69c7472 100644
--- a/lib/liquid/expression.rb
+++ b/lib/liquid/expression.rb
@@ -10,25 +10,28 @@ module Liquid
       'empty' => ''
     }.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/
+    SINGLE_QUOTED_STRING = /\A\s*'(.*)'\s*\z/m
+    DOUBLE_QUOTED_STRING = /\A\s*"(.*)"\s*\z/m
+    INTEGERS_REGEX       = /\A\s*(-?\d+)\s*\z/
+    FLOATS_REGEX         = /\A\s*(-?\d[\d\.]+)\s*\z/
+    RANGES_REGEX         = /\A\s*\(\s*(\S+)\s*\.\.\s*(\S+)\s*\)\s*\z/
 
     def self.parse(markup)
-      if LITERALS.key?(markup)
-        LITERALS[markup]
+      case markup
+      when nil
+        nil
+      when SINGLE_QUOTED_STRING, DOUBLE_QUOTED_STRING
+        Regexp.last_match(1)
+      when INTEGERS_REGEX
+        Regexp.last_match(1).to_i
+      when RANGES_REGEX
+        RangeLookup.parse(Regexp.last_match(1), Regexp.last_match(2))
+      when FLOATS_REGEX
+        Regexp.last_match(1).to_f
       else
-        case markup
-        when 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
+        markup = markup.strip
+        if LITERALS.key?(markup)
+          LITERALS[markup]
         else
           VariableLookup.parse(markup)
         end
diff --git a/test/integration/expression_test.rb b/test/integration/expression_test.rb
new file mode 100644
index 0000000..91a0494
--- /dev/null
+++ b/test/integration/expression_test.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class ExpressionTest < Minitest::Test
+  def test_keyword_literals
+    assert_equal(true, parse_and_eval("true"))
+    assert_equal(true, parse_and_eval(" true "))
+  end
+
+  def test_string
+    assert_equal("single quoted", parse_and_eval("'single quoted'"))
+    assert_equal("double quoted", parse_and_eval('"double quoted"'))
+    assert_equal("spaced", parse_and_eval(" 'spaced' "))
+    assert_equal("spaced2", parse_and_eval(' "spaced2" '))
+  end
+
+  def test_int
+    assert_equal(123, parse_and_eval("123"))
+    assert_equal(456, parse_and_eval(" 456 "))
+    assert_equal(12, parse_and_eval("012"))
+  end
+
+  def test_float
+    assert_equal(1.5, parse_and_eval("1.5"))
+    assert_equal(2.5, parse_and_eval(" 2.5 "))
+  end
+
+  def test_range
+    assert_equal(1..2, parse_and_eval("(1..2)"))
+    assert_equal(3..4, parse_and_eval(" ( 3 .. 4 ) "))
+  end
+
+  private
+
+  def parse_and_eval(markup, **assigns)
+    if Liquid::Template.error_mode == :strict
+      p = Liquid::Parser.new(markup)
+      markup = p.expression
+      p.consume(:end_of_string)
+    end
+    expression = Liquid::Expression.parse(markup)
+    context = Liquid::Context.new(assigns)
+    context.evaluate(expression)
+  end
+end

From 26640368e5e1fac5aa66a8f26bdd43b50bac9cc8 Mon Sep 17 00:00:00 2001
From: Ashwin Maroli <ashmaroli@gmail.com>
Date: Wed, 28 Oct 2020 12:45:10 +0530
Subject: [PATCH 7/9] Run workflows for pull requests from repo forks

---
 .github/workflows/liquid.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/liquid.yml b/.github/workflows/liquid.yml
index 00c51a4..c9101eb 100644
--- a/.github/workflows/liquid.yml
+++ b/.github/workflows/liquid.yml
@@ -1,5 +1,5 @@
 name: Liquid
-on: [push]
+on: [push, pull_request]
 jobs:
   test:
     runs-on: ubuntu-latest

From 1d63d5db5fe61320366f7e2c6c6b8d800b930ac5 Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <dylan.smith@shopify.com>
Date: Wed, 28 Oct 2020 10:36:33 -0400
Subject: [PATCH 8/9] Fix a leaky test that set Tempate.error_mode without
 resetting it (#1339)

---
 test/integration/template_test.rb | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/test/integration/template_test.rb b/test/integration/template_test.rb
index 8cc3d79..f13d834 100644
--- a/test/integration/template_test.rb
+++ b/test/integration/template_test.rb
@@ -257,9 +257,8 @@ class TemplateTest < Minitest::Test
   end
 
   def test_nil_value_does_not_raise
-    Liquid::Template.error_mode = :strict
-    t                           = Template.parse("some{{x}}thing")
-    result                      = t.render!({ 'x' => nil }, strict_variables: true)
+    t      = Template.parse("some{{x}}thing", error_mode: :strict)
+    result = t.render!({ 'x' => nil }, strict_variables: true)
 
     assert_equal(0, t.errors.count)
     assert_equal('something', result)

From 7754d5aef57134fd9fe6c36a40f9a5514ecf2874 Mon Sep 17 00:00:00 2001
From: Dylan Thacker-Smith <dylan.smith@shopify.com>
Date: Wed, 28 Oct 2020 10:37:00 -0400
Subject: [PATCH 9/9] Attempt to strict parse variables before lax parsing in
 lax error mode (#1338)

---
 lib/liquid/parser_switching.rb    | 12 ++++++++++++
 lib/liquid/variable.rb            |  2 +-
 test/integration/assign_test.rb   |  5 +++++
 test/integration/variable_test.rb |  5 +++++
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/lib/liquid/parser_switching.rb b/lib/liquid/parser_switching.rb
index 1a8d4ff..78afd58 100644
--- a/lib/liquid/parser_switching.rb
+++ b/lib/liquid/parser_switching.rb
@@ -2,6 +2,18 @@
 
 module Liquid
   module ParserSwitching
+    def strict_parse_with_error_mode_fallback(markup)
+      strict_parse_with_error_context(markup)
+    rescue SyntaxError => e
+      case parse_context.error_mode
+      when :strict
+        raise
+      when :warn
+        parse_context.warnings << e
+      end
+      lax_parse(markup)
+    end
+
     def parse_with_selected_parser(markup)
       case parse_context.error_mode
       when :strict then strict_parse_with_error_context(markup)
diff --git a/lib/liquid/variable.rb b/lib/liquid/variable.rb
index 77d6b0c..891425c 100644
--- a/lib/liquid/variable.rb
+++ b/lib/liquid/variable.rb
@@ -30,7 +30,7 @@ module Liquid
       @parse_context = parse_context
       @line_number   = parse_context.line_number
 
-      parse_with_selected_parser(markup)
+      strict_parse_with_error_mode_fallback(markup)
     end
 
     def raw
diff --git a/test/integration/assign_test.rb b/test/integration/assign_test.rb
index b956fd1..c5a8dd9 100644
--- a/test/integration/assign_test.rb
+++ b/test/integration/assign_test.rb
@@ -48,6 +48,11 @@ class AssignTest < Minitest::Test
     end
   end
 
+  def test_expression_with_whitespace_in_square_brackets
+    source = "{% assign r = a[ 'b' ] %}{{ r }}"
+    assert_template_result('result', source, 'a' => { 'b' => 'result' })
+  end
+
   def test_assign_score_exceeding_resource_limit
     t = Template.parse("{% assign foo = 42 %}{% assign bar = 23 %}")
     t.resource_limits.assign_score_limit = 1
diff --git a/test/integration/variable_test.rb b/test/integration/variable_test.rb
index 168f43a..ad1b28e 100644
--- a/test/integration/variable_test.rb
+++ b/test/integration/variable_test.rb
@@ -21,6 +21,11 @@ class VariableTest < Minitest::Test
     assert_equal('  worked wonderfully  ', template.render!('test' => 'worked wonderfully'))
   end
 
+  def test_expression_with_whitespace_in_square_brackets
+    assert_template_result('result', "{{ a[ 'b' ] }}", 'a' => { 'b' => 'result' })
+    assert_template_result('result', "{{ a[ [ 'b' ] ] }}", 'b' => 'c', 'a' => { 'c' => 'result' })
+  end
+
   def test_ignore_unknown
     template = Template.parse(%({{ test }}))
     assert_equal('', template.render!)