Extract Parser#range_lookup out of Expression.parse

lib/liquid/parser.rb

@@ -58,8 +58,10 @@ module Liquid
         string
       when :number
         number
+      when :open_round
+        range_lookup
       else
-        parse_expression(expression_string)
+        raise SyntaxError, "#{token} is not a valid expression"
       end
     end
 
@@ -88,6 +90,15 @@ module Liquid
       VariableLookup.new(name, lookups, command_flags)
     end
 
+    def range_lookup
+      consume(:open_round)
+      first = expression
+      consume(:dotdot)
+      last = expression
+      consume(:close_round)
+      RangeLookup.create(first, last)
+    end
+
     def expression_string
       token = @tokens[@p]
       case token[0]

lib/liquid/range_lookup.rb

@@ -2,13 +2,15 @@
 
 module Liquid
   class RangeLookup
-    def self.create(start_obj, end_obj, start_markup, end_markup)
+    def self.create(start_obj, end_obj, start_markup = nil, end_markup = nil)
       if start_obj.respond_to?(:evaluate) || end_obj.respond_to?(:evaluate)
         new(start_obj, end_obj)
       else
         begin
           start_obj.to_i..end_obj.to_i
         rescue NoMethodError
+          start_markup = start_obj.to_s unless start_markup
+          end_markup = end_obj.to_s unless end_markup
           invalid_expr = start_markup unless start_obj.respond_to?(:to_i)
           invalid_expr ||= end_markup unless end_obj.respond_to?(:to_i)
           if invalid_expr

test/integration/expression_test.rb

@@ -46,7 +46,7 @@ class ExpressionTest < Minitest::Test
       "{{ (false..true) }}",
     )
     assert_match_syntax_error(
-      "Liquid syntax error (line 1): Invalid expression type '(1..2)' in range expression",
+      "Liquid syntax error (line 1): Invalid expression type '1..2' in range expression",
       "{{ ((1..2)..3) }}",
     )
   end

test/unit/parser_unit_test.rb

@@ -102,6 +102,15 @@ class ParserUnitTest < Minitest::Test
     assert_equal('title', v.lookups[0])
   end
 
+  def test_range_lookup
+    p = new_parser('(0..5) (a..b)')
+    assert_equal((0..5), p.expression)
+
+    r2 = p.expression
+    assert(r2.is_a?(RangeLookup))
+    assert_equal((1..4), r2.evaluate(Context.new({ 'a' => 1, 'b' => 4 })))
+  end
+
   def test_ranges
     p = new_parser("(5..7) (1.5..9.6) (young..old) (hi[5].wat..old)")
     assert_equal('(5..7)', p.expression_string)