From 740241a9970c0238ce77bd4c651c5afdc98692ba Mon Sep 17 00:00:00 2001
From: Mike Angell <mike.angell@shopify.com>
Date: Tue, 17 Sep 2019 01:59:55 +1000
Subject: [PATCH] Enable Instance Assigns to survive many renders

---
 lib/liquid/template.rb            |  5 +++--
 test/integration/template_test.rb | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lib/liquid/template.rb b/lib/liquid/template.rb
index 286dbd23..58fb94f8 100644
--- a/lib/liquid/template.rb
+++ b/lib/liquid/template.rb
@@ -143,11 +143,12 @@ module Liquid
     end
 
     def instance_assigns
-      @instance_assigns ||= {}
+      @instance_assigns ||= []
     end
 
     def new_outer_scope
-      @instance_assigns = {}
+      @instance_assigns.unshift(last = {})
+      last
     end
 
     def errors
diff --git a/test/integration/template_test.rb b/test/integration/template_test.rb
index e2b54c79..26c640b2 100644
--- a/test/integration/template_test.rb
+++ b/test/integration/template_test.rb
@@ -42,6 +42,18 @@ class TemplateTest < Minitest::Test
     assert_equal 'from instance assigns', t.parse("{{ foo }}").render!
   end
 
+  def test_instance_assigns_persist_on_same_template_object_between_many_parses
+    t = Template.new
+    assert_equal 'from instance assigns', t.parse("{% assign foo = 'from instance assigns' %}{{ foo }}").render!
+    assert_equal 'from instance assigns', t.parse("{{ foo }}").render!
+    assert_equal 'from instance assigns', t.parse("{{ foo }}").render!
+    assert_equal 'from instance assigns', t.parse("{{ foo }}").render!
+    assert_equal 'from instance assigns second', t.parse("{% assign foo = 'from instance assigns second' %}{{ foo }}").render!
+    assert_equal 'from instance assigns second', t.parse("{{ foo }}").render!
+    assert_equal 'from instance assigns second', t.parse("{{ foo }}").render!
+    assert_equal 'from instance assigns second', t.parse("{{ foo }}").render!
+  end
+
   def test_warnings_is_not_exponential_time
     str = "false"
     100.times do
@@ -58,6 +70,14 @@ class TemplateTest < Minitest::Test
     assert_equal 'foofoo', t.render!
   end
 
+  def test_instance_assigns_persist_on_same_template_parsing_between_many_renders
+    t = Template.new.parse("{{ foo }}{% assign foo = 'foo' %}{{ foo }}")
+    assert_equal 'foo', t.render!
+    assert_equal 'foofoo', t.render!
+    assert_equal 'foofoo', t.render!
+    assert_equal 'foofoo', t.render!
+  end
+
   def test_custom_assigns_do_not_persist_on_same_template
     t = Template.new
     assert_equal 'from custom assigns', t.parse("{{ foo }}").render!('foo' => 'from custom assigns')