Use ExpressionParser in the ParseContext when parsing in :rigid mode

lib/liquid/parse_context.rb

@@ -52,26 +52,21 @@ module Liquid
 
     def parse_expression(markup)
       if @error_mode == :rigid
-        parser = new_parser(markup)
-
-        # Return nil immediately if the markup is empty or contains only
-        # whitespaces
-        return if parser.look(:end_of_string)
-
-        expression_string = parser.expression
-
-        # In rigid mode, verify that all tokens have been consumed
+        # ExpressionParser doesn't use @expression_cache because rigid mode
+        # must run Lexer and Parser validation on every call to ensure all
+        # tokens are valid and properly consumed.
         #
-        # Extra tokens remaining after the expression indicate invalid syntaxes,
-        # such as: "product title" (instead of "product.title")
-        parser.consume(:end_of_string) unless parser.look(:end_of_string)
-
-        # Use Parser for strict token validation, but still return
-        # Expression objects for compatibility with the rendering pipeline.
-        markup = expression_string
+        # The expensive operations (tokenization and validation) cannot be
+        # cached, while the cheap operation (building Expression objects from
+        # validated tokens) provides minimal benefit from caching.
+        #
+        # Most importantly, caching would skip the validation step entirely,
+        # which defeats the core purpose of rigid mode: strict validation of
+        # every expression to catch syntax errors like "product title".
+        ExpressionParser.parse(markup, self)
+      else
+        Expression.parse(markup, @string_scanner, @expression_cache)
       end
-
-      Expression.parse(markup, @string_scanner, @expression_cache)
     end
 
     def partial=(value)

test/integration/expression_test.rb

@@ -42,14 +42,25 @@ class ExpressionTest < Minitest::Test
     assert_template_result("3..4", "{{ ( 3 .. 4 ) }}")
     assert_expression_result(1..2, "(1..2)")
 
-    assert_match_syntax_error(
-      "Liquid syntax error (line 1): Invalid expression type 'false' in range expression",
-      "{{ (false..true) }}",
-    )
-    assert_match_syntax_error(
-      "Liquid syntax error (line 1): Invalid expression type '(1..2)' in range expression",
-      "{{ ((1..2)..3) }}",
-    )
+    if Liquid::Environment.default.error_mode == :rigid
+      assert_match_syntax_error(
+        'Invalid expression type in range expression in "{{ (false..true) }}"',
+        "{{ (false..true) }}",
+      )
+      assert_match_syntax_error(
+        'Liquid syntax error (line 1): Invalid expression type in range expression in "{{ ((1..2)..3) }}"',
+        "{{ ((1..2)..3) }}",
+      )
+    else
+      assert_match_syntax_error(
+        "Liquid syntax error (line 1): Invalid expression type 'false' in range expression",
+        "{{ (false..true) }}",
+      )
+      assert_match_syntax_error(
+        "Liquid syntax error (line 1): Invalid expression type '(1..2)' in range expression",
+        "{{ ((1..2)..3) }}",
+      )
+    end
   end
 
   def test_quirky_negative_sign_expression_markup
@@ -66,6 +77,7 @@ class ExpressionTest < Minitest::Test
 
   def test_expression_cache
     skip("Liquid-C does not support Expression caching") if defined?(Liquid::C) && Liquid::C.enabled
+    skip("Rigid mode does not use Expression caching") if Liquid::Environment.default.error_mode == :rigid
 
     cache = {}
     template = <<~LIQUID
@@ -87,6 +99,7 @@ class ExpressionTest < Minitest::Test
 
   def test_expression_cache_with_true_boolean
     skip("Liquid-C does not support Expression caching") if defined?(Liquid::C) && Liquid::C.enabled
+    skip("Rigid mode does not use Expression caching") if Liquid::Environment.default.error_mode == :rigid
 
     template = <<~LIQUID
       {% assign x = 1 %}
@@ -111,6 +124,7 @@ class ExpressionTest < Minitest::Test
 
   def test_expression_cache_with_lru_redux
     skip("Liquid-C does not support Expression caching") if defined?(Liquid::C) && Liquid::C.enabled
+    skip("Rigid mode does not use Expression caching") if Liquid::Environment.default.error_mode == :rigid
 
     cache = LruRedux::Cache.new(10)
     template = <<~LIQUID
@@ -132,6 +146,7 @@ class ExpressionTest < Minitest::Test
 
   def test_disable_expression_cache
     skip("Liquid-C does not support Expression caching") if defined?(Liquid::C) && Liquid::C.enabled
+    skip("Rigid mode does not use Expression caching") if Liquid::Environment.default.error_mode == :rigid
 
     template = <<~LIQUID
       {% assign x = 1 %}