Fixed #32294 -- Prevented ManyToManyField's hidden related name collisions between apps.

django/db/models/fields/related.py

@@ -1614,7 +1614,11 @@ class ManyToManyField(RelatedField):
             # related_name with one generated from the m2m field name. Django
             # still uses backwards relations internally and we need to avoid
             # clashes between multiple m2m fields with related_name == '+'.
-            self.remote_field.related_name = "_%s_%s_+" % (cls.__name__.lower(), name)
+            self.remote_field.related_name = '_%s_%s_%s_+' % (
+                cls._meta.app_label,
+                cls.__name__.lower(),
+                name,
+            )
 
         super().contribute_to_class(cls, name, **kwargs)
 

tests/invalid_models_tests/test_relative_fields.py

@@ -3,7 +3,7 @@ from unittest import mock
 from django.core.checks import Error, Warning as DjangoWarning
 from django.db import connection, models
 from django.test.testcases import SimpleTestCase
-from django.test.utils import isolate_apps, override_settings
+from django.test.utils import isolate_apps, modify_settings, override_settings
 
 
 @isolate_apps('invalid_models_tests')
@@ -1025,6 +1025,32 @@ class ReverseQueryNameClashTests(SimpleTestCase):
             ),
         ])
 
+    @modify_settings(INSTALLED_APPS={'append': 'basic'})
+    @isolate_apps('basic', 'invalid_models_tests')
+    def test_no_clash_across_apps_without_accessor(self):
+        class Target(models.Model):
+            class Meta:
+                app_label = 'invalid_models_tests'
+
+        class Model(models.Model):
+            m2m = models.ManyToManyField(Target, related_name='+')
+
+            class Meta:
+                app_label = 'basic'
+
+        def _test():
+            # Define model with the same name.
+            class Model(models.Model):
+                m2m = models.ManyToManyField(Target, related_name='+')
+
+                class Meta:
+                    app_label = 'invalid_models_tests'
+
+            self.assertEqual(Model.check(), [])
+
+        _test()
+        self.assertEqual(Model.check(), [])
+
 
 @isolate_apps('invalid_models_tests')
 class ExplicitRelatedNameClashTests(SimpleTestCase):

tests/model_meta/results.py

@@ -321,7 +321,7 @@ TEST_RESULTS = {
     'get_all_related_objects_with_model_hidden_local': {
         Person: (
             ('+', None),
-            ('_relating_people_hidden_+', None),
+            ('_model_meta_relating_people_hidden_+', None),
             ('Person_following_inherited+', None),
             ('Person_following_inherited+', None),
             ('Person_friends_inherited+', None),
@@ -339,7 +339,7 @@ TEST_RESULTS = {
         ),
         ProxyPerson: (
             ('+', Person),
-            ('_relating_people_hidden_+', Person),
+            ('_model_meta_relating_people_hidden_+', Person),
             ('Person_following_inherited+', Person),
             ('Person_following_inherited+', Person),
             ('Person_friends_inherited+', Person),
@@ -357,7 +357,7 @@ TEST_RESULTS = {
         ),
         BasePerson: (
             ('+', None),
-            ('_relating_basepeople_hidden_+', None),
+            ('_model_meta_relating_basepeople_hidden_+', None),
             ('BasePerson_following_abstract+', None),
             ('BasePerson_following_abstract+', None),
             ('BasePerson_following_base+', None),
@@ -408,8 +408,8 @@ TEST_RESULTS = {
         Person: (
             ('+', BasePerson),
             ('+', None),
-            ('_relating_basepeople_hidden_+', BasePerson),
+            ('_model_meta_relating_basepeople_hidden_+', BasePerson),
-            ('_relating_people_hidden_+', None),
+            ('_model_meta_relating_people_hidden_+', None),
             ('BasePerson_following_abstract+', BasePerson),
             ('BasePerson_following_abstract+', BasePerson),
             ('BasePerson_following_base+', BasePerson),
@@ -446,8 +446,8 @@ TEST_RESULTS = {
         ProxyPerson: (
             ('+', BasePerson),
             ('+', Person),
-            ('_relating_basepeople_hidden_+', BasePerson),
+            ('_model_meta_relating_basepeople_hidden_+', BasePerson),
-            ('_relating_people_hidden_+', Person),
+            ('_model_meta_relating_people_hidden_+', Person),
             ('BasePerson_following_abstract+', BasePerson),
             ('BasePerson_following_abstract+', BasePerson),
             ('BasePerson_following_base+', BasePerson),
@@ -483,7 +483,7 @@ TEST_RESULTS = {
         ),
         BasePerson: (
             ('+', None),
-            ('_relating_basepeople_hidden_+', None),
+            ('_model_meta_relating_basepeople_hidden_+', None),
             ('BasePerson_following_abstract+', None),
             ('BasePerson_following_abstract+', None),
             ('BasePerson_following_base+', None),
@@ -822,7 +822,7 @@ TEST_RESULTS = {
             ('friends_base_rel_+', None),
             ('followers_base', None),
             ('relating_basepeople', None),
-            ('_relating_basepeople_hidden_+', None),
+            ('_model_meta_relating_basepeople_hidden_+', None),
         ),
         Person: (
             ('friends_abstract_rel_+', BasePerson),
@@ -830,7 +830,7 @@ TEST_RESULTS = {
             ('friends_base_rel_+', BasePerson),
             ('followers_base', BasePerson),
             ('relating_basepeople', BasePerson),
-            ('_relating_basepeople_hidden_+', BasePerson),
+            ('_model_meta_relating_basepeople_hidden_+', BasePerson),
             ('friends_inherited_rel_+', None),
             ('followers_concrete', None),
             ('relating_people', None),
@@ -849,7 +849,7 @@ TEST_RESULTS = {
             'friends_base_rel_+',
             'followers_base',
             'relating_basepeople',
-            '_relating_basepeople_hidden_+',
+            '_model_meta_relating_basepeople_hidden_+',
         ],
         Person: [
             'friends_inherited_rel_+',

tests/model_meta/tests.py

@@ -257,7 +257,7 @@ class RelationTreeTests(SimpleTestCase):
         self.assertEqual(
             sorted(field.related_query_name() for field in BasePerson._meta._relation_tree),
             sorted([
-                '+', '_relating_basepeople_hidden_+', 'BasePerson_following_abstract+',
+                '+', '_model_meta_relating_basepeople_hidden_+', 'BasePerson_following_abstract+',
                 'BasePerson_following_abstract+', 'BasePerson_following_base+', 'BasePerson_following_base+',
                 'BasePerson_friends_abstract+', 'BasePerson_friends_abstract+', 'BasePerson_friends_base+',
                 'BasePerson_friends_base+', 'BasePerson_m2m_abstract+', 'BasePerson_m2m_base+', 'Relating_basepeople+',