fix: Fixed RecursionError when extending templates (django-cms#7594)

* fix: Fixed RecursionError when extending templates with higher depth

* triv: sort imports

* triv: imports sort

* triv: run ruff cms

* triv: changed import to import from

* triv: run ruff cms

---------

Co-authored-by: viliam mihalik <viliam.mihalik@smartbase.sk>
Co-authored-by: Vinit Kumar <vinit.kumar@kidskonnect.nl>

Author: mihalikv

cms/test_utils/project/placeholderapp/nested_placeholderapp/__init__.py

@@ -0,0 +1,16 @@
+{% extends "placeholder_tests/nested_extend.html" %}
+
+{% load cms_tags %}
+
+{% comment %}
+This file should result in following placeholders:
+
+    - recursed_one   (from cms/test_utils/project/placeholderapp/nested_placeholderapp/templates/placeholder_tests/nested_extend.html)
+    - two            (from cms/test_utils/project/placeholderapp/templates/placeholder_tests/nested_extend.html)
+    - recursed_three (from cms/test_utils/project/placeholderapp/templates/placeholder_tests/nested_extend.html)
+
+{% endcomment %}
+
+{% block one %}
+    {% placeholder "recursed_one" %}
+{% endblock %}

cms/test_utils/project/placeholderapp/nested_placeholderapp/templates/placeholder_tests/nested_extend.html

@@ -0,0 +1,16 @@
+{% extends "placeholder_tests/nested_extend.html" %}
+
+{% load cms_tags %}
+
+{% comment %}
+This file should result in following placeholders:
+
+    - recursed_one   (from cms/test_utils/project/placeholderapp/nested_placeholderapp/templates/placeholder_tests/nested_extend.html)
+    - two            (from cms/test_utils/project/placeholderapp/templates/placeholder_tests/nested_extend.html)
+    - recursed_three (from cms/test_utils/project/placeholderapp/templates/placeholder_tests/nested_extend.html)
+
+{% endcomment %}
+
+{% block three %}
+    {% placeholder "recursed_three" %}
+{% endblock %}

cms/test_utils/project/placeholderapp/templates/placeholder_tests/nested_extend.html

@@ -0,0 +1,15 @@
+{% load cms_tags %}
+
+{% block one %}
+	{% placeholder "one" %}
+{% endblock %}
+
+{% block two %}
+	{% placeholder "two" %}
+{% endblock %}
+
+{% block three %}
+	{% placeholder "three" %}
+{% endblock %}
+
+{% block four %}{% endblock %}

cms/test_utils/project/templates/placeholder_tests/nested_extend.html

@@ -1,3 +1,6 @@
+import copy
+import os
+
 from django.conf import settings
 from django.contrib.auth import get_user_model
 from django.core.cache import cache
@@ -10,6 +13,7 @@
 from django.utils.numberformat import format
 from sekizai.context import SekizaiContext
 
+from cms import __file__ as cms_root_path
 from cms import constants
 from cms.api import add_plugin, create_page, create_title
 from cms.exceptions import DuplicatePlaceholderWarning, PluginLimitReached
@@ -116,6 +120,19 @@ def test_placeholder_recursive_extend(self):
         placeholders = _get_placeholder_slots('placeholder_tests/recursive_extend.html')
         self.assertEqual(sorted(placeholders), sorted(['recursed_one', 'recursed_two', 'three']))
 
+    def test_placeholder_recursive_deeper_extend(self):
+        template_settings = copy.deepcopy(settings.TEMPLATES)
+        cms_root_dir = os.path.dirname(cms_root_path)
+        template_settings[0]["DIRS"] = [
+            os.path.join(cms_root_dir, 'test_utils', 'project', 'placeholderapp',
+                         'nested_placeholderapp', 'templates'),
+            os.path.join(cms_root_dir, 'test_utils', 'project', 'placeholderapp', 'templates'),
+            os.path.join(cms_root_dir, 'test_utils', 'project', 'templates'),
+        ]
+        with override_settings(TEMPLATES=template_settings):
+            placeholders = _get_placeholder_slots('placeholder_tests/nested_extend.html')
+            self.assertEqual(sorted(placeholders), sorted(['recursed_one', 'two', 'recursed_three']))
+
     def test_placeholder_scanning_sekizai_extend_outside_block(self):
         placeholders = _get_placeholder_slots('placeholder_tests/outside_sekizai.html')
         self.assertEqual(sorted(placeholders), sorted(['new_one', 'two', 'base_outside']))

cms/tests/test_placeholder.py

@@ -273,16 +273,18 @@ def get_static_placeholders(template, context):
     return placeholders_with_code
 
 
-def _get_block_nodes(extend_node):
-    parent = extend_node.get_parent(get_context(extend_node))
+def _get_block_nodes(extend_node, previous_context=None):
+    if not previous_context:
+        previous_context = get_context(extend_node)
+    parent = extend_node.get_parent(previous_context)
     parent_nodelist = _get_nodelist(parent)
     parent_nodes = parent_nodelist.get_nodes_by_type(BlockNode)
     parent_extend_nodes = parent_nodelist.get_nodes_by_type(ExtendsNode)
 
     if parent_extend_nodes:
         # Start at the top
         # Scan the extends node from the parent (if any)
-        nodes = _get_block_nodes(parent_extend_nodes[0])
+        nodes = _get_block_nodes(parent_extend_nodes[0], previous_context=previous_context)
     else:
         nodes = OrderedDict()
 
@@ -322,10 +324,12 @@ def _get_placeholder_nodes_from_extend(extend_node, node_class):
     return placeholders
 
 
-def _find_topmost_template(extend_node):
-    parent_template = extend_node.get_parent(get_context(extend_node))
+def _find_topmost_template(extend_node, previous_context=None):
+    if not previous_context:
+        previous_context = get_context(extend_node)
+    parent_template = extend_node.get_parent(previous_context)
     for node in _get_nodelist(parent_template).get_nodes_by_type(ExtendsNode):
         # Their can only be one extend block in a template, otherwise django raises an exception
-        return _find_topmost_template(node)
-        # No ExtendsNode
-    return extend_node.get_parent(get_context(extend_node))
+        return _find_topmost_template(node, previous_context=previous_context)
+    # No ExtendsNode
+    return parent_template