Fixed #26088 -- Made autodector detect changing proxy model to MTI.

2 files changed, 86 insertions, 0 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index ae88a90465..c863dcaead 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -612,6 +612,20 @@ class MigrationAutodetector(object):
                     ]
                 )
 
+            # Fix relationships if the model changed from a proxy model to a
+            # concrete model.
+            if (app_label, model_name) in self.old_proxy_keys:
+                for related_object in model_opts.related_objects:
+                    self.add_operation(
+                        related_object.related_model._meta.app_label,
+                        operations.AlterField(
+                            model_name=related_object.related_model._meta.object_name,
+                            name=related_object.field.name,
+                            field=related_object.field,
+                        ),
+                        dependencies=[(app_label, model_name, None, True)],
+                    )
+
     def generate_created_proxies(self):
         """
         Makes CreateModel statements for proxy models.
diff --git a/tests/migrations/test_autodetector.py b/tests/migrations/test_autodetector.py
index 68c4e85b6d..7265330057 100644
--- a/tests/migrations/test_autodetector.py
+++ b/tests/migrations/test_autodetector.py
@@ -240,6 +240,7 @@ class AutodetectorTests(TestCase):
     }, ("testapp.author", ))
     author_proxy_notproxy = ModelState("testapp", "AuthorProxy", [], {}, ("testapp.author", ))
     author_proxy_third = ModelState("thirdapp", "AuthorProxy", [], {"proxy": True}, ("testapp.author", ))
+    author_proxy_third_notproxy = ModelState("thirdapp", "AuthorProxy", [], {}, ("testapp.author", ))
     author_proxy_proxy = ModelState("testapp", "AAuthorProxyProxy", [], {"proxy": True}, ("testapp.authorproxy", ))
     author_unmanaged = ModelState("testapp", "AuthorUnmanaged", [], {"managed": False}, ("testapp.author", ))
     author_unmanaged_managed = ModelState("testapp", "AuthorUnmanaged", [], {}, ("testapp.author", ))
@@ -336,6 +337,10 @@ class AutodetectorTests(TestCase):
         ("author", models.ForeignKey("thirdapp.AuthorProxy", models.CASCADE)),
         ("title", models.CharField(max_length=200)),
     ])
+    book_proxy_proxy_fk = ModelState("otherapp", "Book", [
+        ("id", models.AutoField(primary_key=True)),
+        ("author", models.ForeignKey("testapp.AAuthorProxyProxy", models.CASCADE)),
+    ])
     book_migrations_fk = ModelState("otherapp", "Book", [
         ("id", models.AutoField(primary_key=True)),
         ("author", models.ForeignKey("migrations.UnmigratedModel", models.CASCADE)),
@@ -1291,6 +1296,73 @@ class AutodetectorTests(TestCase):
         # The field name the FK on the book model points to
         self.assertEqual(changes['otherapp'][0].operations[0].fields[2][1].remote_field.field_name, 'pk_field')
 
+    def test_proxy_to_mti_with_fk_to_proxy(self):
+        # First, test the pk table and field name.
+        changes = self.get_changes(
+            [],
+            [self.author_empty, self.author_proxy_third, self.book_proxy_fk],
+        )
+        self.assertEqual(
+            changes['otherapp'][0].operations[0].fields[2][1].remote_field.model._meta.db_table,
+            'testapp_author',
+        )
+        self.assertEqual(changes['otherapp'][0].operations[0].fields[2][1].remote_field.field_name, 'id')
+
+        # Change AuthorProxy to use MTI.
+        changes = self.get_changes(
+            [self.author_empty, self.author_proxy_third, self.book_proxy_fk],
+            [self.author_empty, self.author_proxy_third_notproxy, self.book_proxy_fk],
+        )
+        # Right number/type of migrations for the AuthorProxy model?
+        self.assertNumberMigrations(changes, 'thirdapp', 1)
+        self.assertOperationTypes(changes, 'thirdapp', 0, ['DeleteModel', 'CreateModel'])
+        # Right number/type of migrations for the Book model with a FK to
+        # AuthorProxy?
+        self.assertNumberMigrations(changes, 'otherapp', 1)
+        self.assertOperationTypes(changes, 'otherapp', 0, ['AlterField'])
+        # otherapp should depend on thirdapp.
+        self.assertMigrationDependencies(changes, 'otherapp', 0, [('thirdapp', 'auto_1')])
+        # Now, test the pk table and field name.
+        self.assertEqual(
+            changes['otherapp'][0].operations[0].field.remote_field.model._meta.db_table,
+            'thirdapp_authorproxy',
+        )
+        self.assertEqual(changes['otherapp'][0].operations[0].field.remote_field.field_name, 'author_ptr')
+
+    def test_proxy_to_mti_with_fk_to_proxy_proxy(self):
+        # First, test the pk table and field name.
+        changes = self.get_changes(
+            [],
+            [self.author_empty, self.author_proxy, self.author_proxy_proxy, self.book_proxy_proxy_fk],
+        )
+        self.assertEqual(
+            changes['otherapp'][0].operations[0].fields[1][1].remote_field.model._meta.db_table,
+            'testapp_author',
+        )
+        self.assertEqual(changes['otherapp'][0].operations[0].fields[1][1].remote_field.field_name, 'id')
+
+        # Change AuthorProxy to use MTI. FK still points to AAuthorProxyProxy,
+        # a proxy of AuthorProxy.
+        changes = self.get_changes(
+            [self.author_empty, self.author_proxy, self.author_proxy_proxy, self.book_proxy_proxy_fk],
+            [self.author_empty, self.author_proxy_notproxy, self.author_proxy_proxy, self.book_proxy_proxy_fk],
+        )
+        # Right number/type of migrations for the AuthorProxy model?
+        self.assertNumberMigrations(changes, 'testapp', 1)
+        self.assertOperationTypes(changes, 'testapp', 0, ['DeleteModel', 'CreateModel'])
+        # Right number/type of migrations for the Book model with a FK to
+        # AAuthorProxyProxy?
+        self.assertNumberMigrations(changes, 'otherapp', 1)
+        self.assertOperationTypes(changes, 'otherapp', 0, ['AlterField'])
+        # otherapp should depend on testapp.
+        self.assertMigrationDependencies(changes, 'otherapp', 0, [('testapp', 'auto_1')])
+        # Now, test the pk table and field name.
+        self.assertEqual(
+            changes['otherapp'][0].operations[0].field.remote_field.model._meta.db_table,
+            'testapp_authorproxy',
+        )
+        self.assertEqual(changes['otherapp'][0].operations[0].field.remote_field.field_name, 'author_ptr')
+
     def test_unmanaged_create(self):
         """Tests that the autodetector correctly deals with managed models."""
         # First, we test adding an unmanaged model