Fixed ranges and added for loop parser

lib/liquid/lexer.rb

@@ -7,7 +7,9 @@ module Liquid
       ':' => :colon,
       ',' => :comma,
       '[' => :open_square,
-      ']' => :close_square
+      ']' => :close_square,
+      '(' => :open_round,
+      ')' => :close_round
     }
     IDENTIFIER = /[\w\-?!]+/
     SINGLE_STRING_LITERAL = /'[^\']*'/

lib/liquid/parser.rb

@@ -50,21 +50,22 @@ module Liquid
 
     def expression
       token = @tokens[@p]
-      str = if token[0] == :id
+      if token[0] == :id
         variable_signature
       elsif [:string, :number].include? token[0]
         consume
         token[1]
+      elsif token.first == :open_round
+        consume
+        first = expression
+        consume(:dot)
+        consume(:dot)
+        last = expression
+        consume(:close_round)
+        "(#{first}..#{last})"
       else
         raise SyntaxError, "#{token} is not a valid expression."
       end
-
-      if look(:dot) && look(:dot, 1)
-        @p += 2
-        str + expression
-      else
-        str
-      end
     end
 
     def argument

lib/liquid/tags/for.rb

@@ -47,19 +47,7 @@ module Liquid
     Syntax = /\A(#{VariableSegment}+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
 
     def initialize(tag_name, markup, tokens)
-      if markup =~ Syntax
-        @variable_name = $1
-        @collection_name = $2
-        @name = "#{$1}-#{$2}"
-        @reversed = $3
-        @attributes = {}
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = value
-        end
-      else
-        raise SyntaxError.new("Syntax Error in 'for loop' - Valid syntax: for [item] in [collection]")
-      end
-
+      switch_parse(markup)
       @nodelist = @for_block = []
       super
     end
@@ -127,6 +115,43 @@ module Liquid
       result
     end
 
+    protected
+
+    def lax_parse(markup)
+      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
+    end
+
+    def strict_parse(markup)
+      p = Parser.new(markup)
+      @variable_name = p.consume(:id)
+      raise SyntaxError, "For loops require an 'in' clause" unless p.id?('in')
+      @collection_name = p.expression
+      @name = "#{@variable_name}-#{@collection_name}"
+      @reversed = p.id?('reversed')
+
+      @attributes = {}
+      while p.look(:id) && p.look(:colon, 1)
+        unless attribute = p.id?('limit') || p.id?('offset')
+          raise SyntaxError, "Invalid attribute in for loop. Valid attributes are limit and offset"
+        end
+        p.consume
+        val = p.expression
+        @attributes[attribute] = val
+      end
+      p.consume(:end_of_string)
+    end
+
     private
 
       def render_else(context)