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

@@ -45,8 +45,8 @@ module Liquid
       @@operators
     end
 
-    def self.parse_expression(markup)
+    def self.parse_expression(parse_context, markup)
-      @@method_literals[markup] || Expression.parse(markup)
+      @@method_literals[markup] || parse_context.parse_expression(markup)
     end
 
     attr_reader :attachment, :child_condition

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

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

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

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
 

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
 

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)

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
+        @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
-        @template_name_expr = Expression.parse(template_name)
+        @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

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
+      @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
-      @template_name_expr = Expression.parse(template_name)
+      @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
 

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")