From c698474abc9ab004812f78b8adee4d5c16e9f7b1 Mon Sep 17 00:00:00 2001
From: Guilherme Carreiro <guilherme.carreiro@shopify.com>
Date: Wed, 6 May 2026 09:49:30 +0200
Subject: [PATCH] Prevent `SelfDrop` context mutation across render boundaries

---
 lib/liquid/self_drop.rb            |  8 ++--
 test/integration/self_drop_test.rb | 71 ++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 4 deletions(-)
 create mode 100644 test/integration/self_drop_test.rb

diff --git a/lib/liquid/self_drop.rb b/lib/liquid/self_drop.rb
index 35781465..fa3fa27a 100644
--- a/lib/liquid/self_drop.rb
+++ b/lib/liquid/self_drop.rb
@@ -16,19 +16,19 @@ module Liquid
   #   then the local value takes precedence over the `self` object.
   # @liquid_access global
   class SelfDrop < Drop
-    def initialize(context)
+    def initialize(self_context)
       super()
-      @context = context
+      @self_context = self_context
     end
 
     def [](key)
-      @context.find_variable(key)
+      @self_context.find_variable(key)
     rescue UndefinedVariable
       nil
     end
 
     def key?(key)
-      @context.variable_defined?(key)
+      @self_context.variable_defined?(key)
     end
 
     def to_liquid
diff --git a/test/integration/self_drop_test.rb b/test/integration/self_drop_test.rb
new file mode 100644
index 00000000..39775546
--- /dev/null
+++ b/test/integration/self_drop_test.rb
@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class SelfDropTest < Minitest::Test
+  include Liquid
+
+  def test_self_drop_passed_as_render_param_preserves_original_scope
+    source = <<~LIQUID
+      {%- assign var = 42 -%}
+      {%- assign s = self -%}
+      {%- render "snippet1", other_self: s -%}
+    LIQUID
+
+    partials = {
+      'snippet1' => <<~LIQUID,
+        {%- assign var = 43 -%}
+        {{- other_self.var }}|{{ self.var -}}
+      LIQUID
+    }
+
+    assert_template_result('42|43', source, partials: partials)
+  end
+
+  def test_self_drop_in_render_without_passing_resolves_inner_scope
+    source = <<~LIQUID
+      {%- assign var = 42 -%}
+      {%- render "snippet1" -%}
+    LIQUID
+
+    partials = {
+      'snippet1' => <<~LIQUID,
+        {%- assign var = 99 -%}
+        {{- self.var -}}
+      LIQUID
+    }
+
+    assert_template_result('99', source, partials: partials)
+  end
+
+  def test_self_drop_passed_to_nested_renders_preserves_each_level
+    source = <<~LIQUID
+      {%- assign a = 1 -%}
+      {%- assign s1 = self -%}
+      {%- render "snippet1", outer: s1 -%}
+    LIQUID
+
+    partials = {
+      'snippet1' => <<~LIQUID,
+        {%- assign a = 2 -%}
+        {%- assign s2 = self -%}
+        {%- render "snippet2", outer: outer, middle: s2 -%}
+      LIQUID
+      'snippet2' => <<~LIQUID,
+        {%- assign a = 3 -%}
+        {{- outer.a }}|{{ middle.a }}|{{ self.a -}}
+      LIQUID
+    }
+
+    assert_template_result('1|2|3', source, partials: partials)
+  end
+
+  def test_self_drop_reflects_variables_assigned_after_creation
+    source = <<~LIQUID
+      {%- assign s = self -%}
+      {%- assign x = 42 %}{{ s.x -}}
+    LIQUID
+
+    assert_template_result('42', source)
+  end
+end