[4.1.x] Fixed #33955, Fixed #33971 -- Reverted "Fixed #32565 -- Moved internal URLResolver view-strings mapping to admindocs."

This reverts commit 7f3cfaa12b28d15c0ca78bb692bfd6e59d17bff1.

Thanks Tom Carrick and Greg Kaleka for reports.
Backport of 974942a75039ba43e618f6a5ff95e08b5d5176fd from main

7 files changed, 54 insertions, 82 deletions

diff --git a/django/contrib/admindocs/apps.py b/django/contrib/admindocs/apps.py
index 2fda5fb4fb..e79dc892cb 100644
--- a/django/contrib/admindocs/apps.py
+++ b/django/contrib/admindocs/apps.py
@@ -1,15 +1,7 @@
 from django.apps import AppConfig
-from django.urls import get_resolver, get_urlconf
 from django.utils.translation import gettext_lazy as _
 
-from .utils import _active, register_callback
-
 
 class AdminDocsConfig(AppConfig):
     name = "django.contrib.admindocs"
     verbose_name = _("Administrative Documentation")
-
-    def ready(self):
-        urlconf = get_urlconf()
-        urlresolver = get_resolver(urlconf)
-        register_callback(urlresolver, _active.local_value)
diff --git a/django/contrib/admindocs/utils.py b/django/contrib/admindocs/utils.py
index a18dbe12cd..6edff502ec 100644
--- a/django/contrib/admindocs/utils.py
+++ b/django/contrib/admindocs/utils.py
@@ -1,15 +1,11 @@
 "Misc. utility functions/classes for admin documentation generator."
 
-import functools
 import re
 from email.errors import HeaderParseError
 from email.parser import HeaderParser
 from inspect import cleandoc
 
-from asgiref.local import Local
-
 from django.urls import reverse
-from django.urls.resolvers import URLPattern
 from django.utils.regex_helper import _lazy_re_compile
 from django.utils.safestring import mark_safe
 
@@ -243,43 +239,3 @@ def remove_non_capturing_groups(pattern):
         final_pattern += pattern[prev_end:start]
         prev_end = end
     return final_pattern + pattern[prev_end:]
-
-
-# Callback strings are cached in a dictionary for every urlconf.
-# The active calback_strs are stored by thread id to make them thread local.
-_callback_strs = set()
-_active = Local()
-_active.local_value = _callback_strs
-
-
-def _is_callback(name, urlresolver=None):
-    if urlresolver and not urlresolver._populated:
-        register_callback(urlresolver, _active.local_value)
-    return name in _active.local_value
-
-
-@functools.lru_cache(maxsize=None)
-def lookup_str(urlpattern):
-    """
-    A string that identifies the view (e.g. 'path.to.view_function' or
-    'path.to.ClassBasedView').
-    """
-    callback = urlpattern.callback
-    if isinstance(callback, functools.partial):
-        callback = callback.func
-    if hasattr(callback, "view_class"):
-        callback = callback.view_class
-    elif not hasattr(callback, "__name__"):
-        return callback.__module__ + "." + callback.__class__.__name__
-    return callback.__module__ + "." + callback.__qualname__
-
-
-def register_callback(urlresolver, thread):
-    for url_pattern in reversed(urlresolver.url_patterns):
-        if isinstance(url_pattern, URLPattern):
-            thread.add(lookup_str(url_pattern))
-        else:  # url_pattern is a URLResolver.
-            _active.url_pattern_value = _callback_strs
-            register_callback(url_pattern, _active.url_pattern_value)
-            thread.update(_active.url_pattern_value)
-    urlresolver._populated = True
diff --git a/django/contrib/admindocs/views.py b/django/contrib/admindocs/views.py
index f771e8f391..1d08541057 100644
--- a/django/contrib/admindocs/views.py
+++ b/django/contrib/admindocs/views.py
@@ -30,7 +30,7 @@ from django.utils.inspect import (
 from django.utils.translation import gettext as _
 from django.views.generic import TemplateView
 
-from .utils import _is_callback, get_view_name
+from .utils import get_view_name
 
 # Exclude methods starting with these strings from documentation
 MODEL_METHODS_EXCLUDE = ("_", "add_", "delete", "save", "set_")
@@ -166,7 +166,8 @@ class ViewDetailView(BaseAdminDocsView):
 
     @staticmethod
     def _get_view_func(view):
-        if _is_callback(view):
+        urlconf = get_urlconf()
+        if get_resolver(urlconf)._is_callback(view):
             mod, func = get_mod_func(view)
             try:
                 # Separate the module and function, e.g.
diff --git a/django/urls/resolvers.py b/django/urls/resolvers.py
index 7c0d4fd85a..9f42e2738c 100644
--- a/django/urls/resolvers.py
+++ b/django/urls/resolvers.py
@@ -437,6 +437,21 @@ class URLPattern:
                 extra_kwargs=self.default_args,
             )
 
+    @cached_property
+    def lookup_str(self):
+        """
+        A string that identifies the view (e.g. 'path.to.view_function' or
+        'path.to.ClassBasedView').
+        """
+        callback = self.callback
+        if isinstance(callback, functools.partial):
+            callback = callback.func
+        if hasattr(callback, "view_class"):
+            callback = callback.view_class
+        elif not hasattr(callback, "__name__"):
+            return callback.__module__ + "." + callback.__class__.__name__
+        return callback.__module__ + "." + callback.__qualname__
+
 
 class URLResolver:
     def __init__(
@@ -454,6 +469,9 @@ class URLResolver:
         self._reverse_dict = {}
         self._namespace_dict = {}
         self._app_dict = {}
+        # set of dotted paths to all functions and classes that are used in
+        # urlpatterns
+        self._callback_strs = set()
         self._populated = False
         self._local = Local()
 
@@ -527,6 +545,7 @@ class URLResolver:
                 if p_pattern.startswith("^"):
                     p_pattern = p_pattern[1:]
                 if isinstance(url_pattern, URLPattern):
+                    self._callback_strs.add(url_pattern.lookup_str)
                     bits = normalize(url_pattern.pattern.regex.pattern)
                     lookups.appendlist(
                         url_pattern.callback,
@@ -585,6 +604,7 @@ class URLResolver:
                             namespaces[namespace] = (p_pattern + prefix, sub_pattern)
                         for app_name, namespace_list in url_pattern.app_dict.items():
                             apps.setdefault(app_name, []).extend(namespace_list)
+                    self._callback_strs.update(url_pattern._callback_strs)
             self._namespace_dict[language_code] = namespaces
             self._app_dict[language_code] = apps
             self._reverse_dict[language_code] = lookups
@@ -629,6 +649,11 @@ class URLResolver:
             route2 = route2[1:]
         return route1 + route2
 
+    def _is_callback(self, name):
+        if not self._populated:
+            self._populate()
+        return name in self._callback_strs
+
     def resolve(self, path):
         path = str(path)  # path may be a reverse_lazy object
         tried = []
diff --git a/docs/releases/4.1.1.txt b/docs/releases/4.1.1.txt
index 2e4782f904..193741762e 100644
--- a/docs/releases/4.1.1.txt
+++ b/docs/releases/4.1.1.txt
@@ -55,3 +55,7 @@ Bugfixes
 
 * Fixed a regression in Django 4.1 that caused a migration crash on SQLite <
   3.20 (:ticket:`33960`).
+
+* Fixed a regression in Django 4.1 that caused an admin crash when the
+  :mod:`~django.contrib.admindocs` app was used (:ticket:`33955`,
+  :ticket:`33971`).
diff --git a/tests/admin_docs/test_utils.py b/tests/admin_docs/test_utils.py
index e26a4ca1f3..18c6769fad 100644
--- a/tests/admin_docs/test_utils.py
+++ b/tests/admin_docs/test_utils.py
@@ -1,15 +1,13 @@
 import unittest
 
 from django.contrib.admindocs.utils import (
-    _is_callback,
     docutils_is_available,
     parse_docstring,
     parse_rst,
 )
 from django.test.utils import captured_stderr
-from django.urls import get_resolver
 
-from .tests import AdminDocsSimpleTestCase, SimpleTestCase
+from .tests import AdminDocsSimpleTestCase
 
 
 @unittest.skipUnless(docutils_is_available, "no docutils installed.")
@@ -121,28 +119,3 @@ class TestUtils(AdminDocsSimpleTestCase):
         markup = "<p>reST, <cite>interpreted text</cite>, default role.</p>\n"
         parts = docutils.core.publish_parts(source=source, writer_name="html4css1")
         self.assertEqual(parts["fragment"], markup)
-
-
-class TestResolver(SimpleTestCase):
-    def test_namespaced_view_detail(self):
-        resolver = get_resolver("urlpatterns_reverse.nested_urls")
-        self.assertTrue(_is_callback("urlpatterns_reverse.nested_urls.view1", resolver))
-        self.assertTrue(_is_callback("urlpatterns_reverse.nested_urls.view2", resolver))
-        self.assertTrue(_is_callback("urlpatterns_reverse.nested_urls.View3", resolver))
-        self.assertFalse(_is_callback("urlpatterns_reverse.nested_urls.blub", resolver))
-
-    def test_view_detail_as_method(self):
-        # Views which have a class name as part of their path.
-        resolver = get_resolver("urlpatterns_reverse.method_view_urls")
-        self.assertTrue(
-            _is_callback(
-                "urlpatterns_reverse.method_view_urls.ViewContainer.method_view",
-                resolver,
-            )
-        )
-        self.assertTrue(
-            _is_callback(
-                "urlpatterns_reverse.method_view_urls.ViewContainer.classmethod_view",
-                resolver,
-            )
-        )
diff --git a/tests/urlpatterns_reverse/tests.py b/tests/urlpatterns_reverse/tests.py
index 73159b6bb8..89dfd0deba 100644
--- a/tests/urlpatterns_reverse/tests.py
+++ b/tests/urlpatterns_reverse/tests.py
@@ -640,6 +640,27 @@ class ResolverTests(SimpleTestCase):
                                 % (e["name"], t.name),
                             )
 
+    def test_namespaced_view_detail(self):
+        resolver = get_resolver("urlpatterns_reverse.nested_urls")
+        self.assertTrue(resolver._is_callback("urlpatterns_reverse.nested_urls.view1"))
+        self.assertTrue(resolver._is_callback("urlpatterns_reverse.nested_urls.view2"))
+        self.assertTrue(resolver._is_callback("urlpatterns_reverse.nested_urls.View3"))
+        self.assertFalse(resolver._is_callback("urlpatterns_reverse.nested_urls.blub"))
+
+    def test_view_detail_as_method(self):
+        # Views which have a class name as part of their path.
+        resolver = get_resolver("urlpatterns_reverse.method_view_urls")
+        self.assertTrue(
+            resolver._is_callback(
+                "urlpatterns_reverse.method_view_urls.ViewContainer.method_view"
+            )
+        )
+        self.assertTrue(
+            resolver._is_callback(
+                "urlpatterns_reverse.method_view_urls.ViewContainer.classmethod_view"
+            )
+        )
+
     def test_populate_concurrency(self):
         """
         URLResolver._populate() can be called concurrently, but not more