Make Parser.expression parse equality expressions

lib/liquid/lexer.rb

@@ -6,14 +6,14 @@ module Liquid
     CLOSE_SQUARE = [:close_square, "]"].freeze
     COLON = [:colon, ":"].freeze
     COMMA = [:comma, ","].freeze
-    COMPARISION_NOT_EQUAL = [:comparison, "!="].freeze
+    COMPARISION_NOT_EQUAL = [:equality, "!="].freeze
     COMPARISON_CONTAINS = [:comparison, "contains"].freeze
-    COMPARISON_EQUAL = [:comparison, "=="].freeze
+    COMPARISON_EQUAL = [:equality, "=="].freeze
     COMPARISON_GREATER_THAN = [:comparison, ">"].freeze
     COMPARISON_GREATER_THAN_OR_EQUAL = [:comparison, ">="].freeze
     COMPARISON_LESS_THAN = [:comparison, "<"].freeze
     COMPARISON_LESS_THAN_OR_EQUAL = [:comparison, "<="].freeze
-    COMPARISON_NOT_EQUAL_ALT = [:comparison, "<>"].freeze
+    COMPARISON_NOT_EQUAL_ALT = [:equality, "<>"].freeze
     DASH = [:dash, "-"].freeze
     DOT = [:dot, "."].freeze
     DOTDOT = [:dotdot, ".."].freeze

lib/liquid/parser.rb

@@ -47,11 +47,21 @@ module Liquid
       tok[0] == type
     end
 
-    # expression := comparison
+    # expression := equality
+    # equality   := comparison (("==" | "!=" | "<>") comparison)*
     # comparison := primary ((">=" | ">" | "<" | "<=" | ... ) primary)*
     # primary    := string | number | variable_lookup | range | boolean
     def expression
-      comparison
+      equality
+    end
+
+    def equality
+      expr = comparison
+      while look(:equality)
+        operator = consume
+        expr = BinaryExpression.new(expr, operator, comparison)
+      end
+      expr
     end
 
     # comparison := primary ((">=" | ">" | "<" | "<=" | ... ) primary)*

lib/liquid/tags/if.rb

@@ -97,7 +97,7 @@ module Liquid
 
     def parse_comparison(p)
       a = parse_expression(p)
-      if (op = p.consume?(:comparison))
+      if (op = p.consume?(:comparison) || p.consume?(:equality))
         b = parse_expression(p)
         Condition.new(a, op, b)
       else