From 859a87d873ce7152af73ab851653b4e1c3ffea4c Mon Sep 17 00:00:00 2001
From: Biel Frontera <bfrontera@socib.es>
Date: Mon, 14 Mar 2022 09:53:36 +0100
Subject: [PATCH] Fixed #31357 -- Fixed get_for_models() crash for stale
 content types when model with the same name exists in another app.

---
 django/contrib/contenttypes/models.py   | 18 ++++++++++++------
 tests/contenttypes_tests/test_models.py | 20 ++++++++++++++++++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/django/contrib/contenttypes/models.py b/django/contrib/contenttypes/models.py
index ef4f30556f..b83c9afcae 100644
--- a/django/contrib/contenttypes/models.py
+++ b/django/contrib/contenttypes/models.py
@@ -2,6 +2,7 @@ from collections import defaultdict
 
 from django.apps import apps
 from django.db import models
+from django.db.models import Q
 from django.utils.translation import gettext_lazy as _
 
 
@@ -64,9 +65,8 @@ class ContentTypeManager(models.Manager):
         Given *models, return a dictionary mapping {model: content_type}.
         """
         results = {}
-        # Models that aren't already in the cache.
-        needed_app_labels = set()
-        needed_models = set()
+        # Models that aren't already in the cache grouped by app labels.
+        needed_models = defaultdict(set)
         # Mapping of opts to the list of models requiring it.
         needed_opts = defaultdict(list)
         for model in models:
@@ -74,14 +74,20 @@ class ContentTypeManager(models.Manager):
             try:
                 ct = self._get_from_cache(opts)
             except KeyError:
-                needed_app_labels.add(opts.app_label)
-                needed_models.add(opts.model_name)
+                needed_models[opts.app_label].add(opts.model_name)
                 needed_opts[opts].append(model)
             else:
                 results[model] = ct
         if needed_opts:
             # Lookup required content types from the DB.
-            cts = self.filter(app_label__in=needed_app_labels, model__in=needed_models)
+            condition = Q(
+                *(
+                    Q(("app_label", app_label), ("model__in", models), _connector=Q.AND)
+                    for app_label, models in needed_models.items()
+                ),
+                _connector=Q.OR,
+            )
+            cts = self.filter(condition)
             for ct in cts:
                 opts_models = needed_opts.pop(ct.model_class()._meta, [])
                 for model in opts_models:
diff --git a/tests/contenttypes_tests/test_models.py b/tests/contenttypes_tests/test_models.py
index e2fb7fe818..a96e12e69f 100644
--- a/tests/contenttypes_tests/test_models.py
+++ b/tests/contenttypes_tests/test_models.py
@@ -248,6 +248,26 @@ class ContentTypesTests(TestCase):
         ct_fetched = ContentType.objects.get_for_id(ct.pk)
         self.assertIsNone(ct_fetched.model_class())
 
+    def test_missing_model_with_existing_model_name(self):
+        """
+        Displaying content types in admin (or anywhere) doesn't break on
+        leftover content type records in the DB for which no model is defined
+        anymore, even if a model with the same name exists in another app.
+        """
+        # Create a stale ContentType that matches the name of an existing
+        # model.
+        ContentType.objects.create(app_label="contenttypes", model="author")
+        ContentType.objects.clear_cache()
+        # get_for_models() should work as expected for existing models.
+        cts = ContentType.objects.get_for_models(ContentType, Author)
+        self.assertEqual(
+            cts,
+            {
+                ContentType: ContentType.objects.get_for_model(ContentType),
+                Author: ContentType.objects.get_for_model(Author),
+            },
+        )
+
     def test_str(self):
         ct = ContentType.objects.get(app_label="contenttypes_tests", model="site")
         self.assertEqual(str(ct), "contenttypes_tests | site")