[1.8.x] Fixed #23441, #24555 -- Improved the behavior of InclusionNode.

This change:

* Makes the InclusionNode cache-safe by removing render-time side effects
  to its nodelist.
* Ensures the render_context stack is properly scoped and reset by updating
  the render call to use Template.render rather than Nodelist.render.

Backport of 0808ccce3808235c5b5a56e3f689cec0d4bc0ebf from master

5 files changed, 37 insertions, 1 deletions

diff --git a/tests/template_tests/templates/inclusion_base.html b/tests/template_tests/templates/inclusion_base.html
new file mode 100644
index 0000000000..795c4dad32
--- /dev/null
+++ b/tests/template_tests/templates/inclusion_base.html
@@ -0,0 +1 @@
+{% block content %}base{% endblock %}
diff --git a/tests/template_tests/templates/inclusion_extends1.html b/tests/template_tests/templates/inclusion_extends1.html
new file mode 100644
index 0000000000..4827f42d3c
--- /dev/null
+++ b/tests/template_tests/templates/inclusion_extends1.html
@@ -0,0 +1,2 @@
+{% extends 'inclusion_base.html' %}
+{% block content %}one{% endblock %}
diff --git a/tests/template_tests/templates/inclusion_extends2.html b/tests/template_tests/templates/inclusion_extends2.html
new file mode 100644
index 0000000000..0ec4d64c04
--- /dev/null
+++ b/tests/template_tests/templates/inclusion_extends2.html
@@ -0,0 +1,2 @@
+{% extends 'inclusion_base.html' %}
+{% block content %}two{% endblock %}
diff --git a/tests/template_tests/templatetags/inclusion.py b/tests/template_tests/templatetags/inclusion.py
index 77c9abeb5c..1631ce92b9 100644
--- a/tests/template_tests/templatetags/inclusion.py
+++ b/tests/template_tests/templatetags/inclusion.py
@@ -164,3 +164,13 @@ def inclusion_tag_without_context_parameter(arg):
     """Expected inclusion_tag_without_context_parameter __doc__"""
     return {}
 inclusion_tag_without_context_parameter.anything = "Expected inclusion_tag_without_context_parameter __dict__"
+
+
+@register.inclusion_tag('inclusion_extends1.html')
+def inclusion_extends1():
+    return {}
+
+
+@register.inclusion_tag('inclusion_extends2.html')
+def inclusion_extends2():
+    return {}
diff --git a/tests/template_tests/test_custom.py b/tests/template_tests/test_custom.py
index 8cf45b68d5..fa485bb674 100644
--- a/tests/template_tests/test_custom.py
+++ b/tests/template_tests/test_custom.py
@@ -2,7 +2,8 @@ from __future__ import unicode_literals
 
 import os
 
-from django.template import Context, Template, TemplateSyntaxError
+from django.template import Context, Engine, Template, TemplateSyntaxError
+from django.template.base import Node
 from django.test import SimpleTestCase, ignore_warnings
 from django.test.utils import extend_sys_path
 from django.utils import six
@@ -274,6 +275,26 @@ class CustomTagTests(SimpleTestCase):
         c.use_l10n = True
         self.assertEqual(t.render(c).strip(), 'True')
 
+    def test_no_render_side_effect(self):
+        """
+        #23441 -- InclusionNode shouldn't modify its nodelist at render time.
+        """
+        engine = Engine(app_dirs=True)
+        template = engine.from_string('{% load inclusion %}{% inclusion_no_params %}')
+        count = template.nodelist.get_nodes_by_type(Node)
+        template.render(Context({}))
+        self.assertEqual(template.nodelist.get_nodes_by_type(Node), count)
+
+    def test_render_context_is_cleared(self):
+        """
+        #24555 -- InclusionNode should push and pop the render_context stack
+        when rendering. Otherwise, leftover values such as blocks from
+        extending can interfere with subsequent rendering.
+        """
+        engine = Engine(app_dirs=True)
+        template = engine.from_string('{% load inclusion %}{% inclusion_extends1 %}{% inclusion_extends2 %}')
+        self.assertEqual(template.render(Context({})).strip(), 'one\ntwo')
+
     def test_assignment_tags(self):
         c = Context({'value': 42})