From c78bf20010e61e2d73e04ee81f391482f5c1094c Mon Sep 17 00:00:00 2001
From: "Charles-P. Clermont" <charles@cpclermont.com>
Date: Tue, 30 Sep 2025 15:46:17 -0400
Subject: [PATCH] Add a rigid_parse method to `cycle`

---
 lib/liquid/tags/cycle.rb                | 53 +++++++++++++++++++------
 test/integration/tags/cycle_tag_test.rb | 15 +++++++
 2 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/lib/liquid/tags/cycle.rb b/lib/liquid/tags/cycle.rb
index c2d94d5f..8f4d0689 100644
--- a/lib/liquid/tags/cycle.rb
+++ b/lib/liquid/tags/cycle.rb
@@ -22,18 +22,7 @@ module Liquid
 
     def initialize(tag_name, markup, options)
       super
-      case markup
-      when NamedSyntax
-        @variables = variables_from_string(Regexp.last_match(2))
-        @name      = parse_expression(Regexp.last_match(1))
-        @is_named = true
-      when SimpleSyntax
-        @variables = variables_from_string(markup)
-        @name      = @variables.to_s
-        @is_named = !@name.match?(/\w+:0x\h{8}/)
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
-      end
+      parse_with_selected_parser(markup)
     end
 
     def named?
@@ -65,6 +54,46 @@ module Liquid
 
     private
 
+    # cycle [name:] expression(, expression)*
+    def rigid_parse(markup)
+      $stderr.puts "using rigid"
+      p = @parse_context.new_parser(markup)
+
+      if p.look(:id) && p.peek(1) == :colon
+        @name = p.consume(:id)
+        @is_named = true
+        p.consume(:colon)
+      end
+
+      @variables = []
+      while (var = p.expression)
+        @variables << var
+        break unless p.consume?(:comma)
+      end
+
+      raise_syntax_error(options) if @variables.empty?
+    end
+
+    # Temporarily until we migrate
+    def strict_parse(markup)
+      lax_parse(markup)
+    end
+
+    def lax_parse(markup)
+      case markup
+      when NamedSyntax
+        @variables = variables_from_string(Regexp.last_match(2))
+        @name      = parse_expression(Regexp.last_match(1))
+        @is_named = true
+      when SimpleSyntax
+        @variables = variables_from_string(markup)
+        @name      = @variables.to_s
+        @is_named = !@name.match?(/\w+:0x\h{8}/)
+      else
+        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
+      end
+    end
+
     def variables_from_string(markup)
       markup.split(',').collect do |var|
         var =~ /\s*(#{QuotedFragment})\s*/o
diff --git a/test/integration/tags/cycle_tag_test.rb b/test/integration/tags/cycle_tag_test.rb
index a034db17..8cd6daac 100644
--- a/test/integration/tags/cycle_tag_test.rb
+++ b/test/integration/tags/cycle_tag_test.rb
@@ -45,4 +45,19 @@ class CycleTagTest < Minitest::Test
 
     assert_template_result("11", template)
   end
+
+  def test_cycle_tag_with_error_mode
+    # QuotedFragment is more permissive than what Parser#expression allows.
+    [:lax, :strict].each do |mode|
+      with_error_mode(mode) do
+        assert_template_result("a", "{% cycle .5: 'a', 'b' %}")
+        assert_template_result("b", "{% assign 5 = 'b' %}{% cycle .5, .4 %}")
+      end
+    end
+
+    with_error_mode(:rigid) do
+      assert_raises(Liquid::SyntaxError) { Template.parse("{% cycle .5: 'a', 'b' %}") }
+      assert_raises(Liquid::SyntaxError) { Template.parse("{% cycle .5, .4 %}") }
+    end
+  end
 end