[1.7.x] Fixed #22331 -- Made MigrationAutodetector ignore unmanaged m…

…odels.

This commit reverts 69d4b1c and tackle the issue from a different angle.
Models remain present in the project state, but are now ignored by the
autodetector.

Backport of 42336c8 from master

django/db/migrations/autodetector.py

@@ -51,16 +51,17 @@ def _detect_changes(self):
         new_apps = self.to_state.render()
         # Prepare lists of old/new model keys that we care about
         # (i.e. ignoring proxy ones)
-        old_model_keys = [
-            (al, mn)
-            for al, mn in self.from_state.models.keys()
-            if not old_apps.get_model(al, mn)._meta.proxy
-        ]
-        new_model_keys = [
-            (al, mn)
-            for al, mn in self.to_state.models.keys()
-            if not new_apps.get_model(al, mn)._meta.proxy
-        ]
+        old_model_keys = []
+        for al, mn in self.from_state.models.keys():
+            model = old_apps.get_model(al, mn)
+            if not model._meta.proxy and model._meta.managed:
+                old_model_keys.append((al, mn))
+
+        new_model_keys = []
+        for al, mn in self.to_state.models.keys():
+            model = new_apps.get_model(al, mn)
+            if not model._meta.proxy and model._meta.managed:
+                new_model_keys.append((al, mn))
 
         def _rel_agnostic_fields_def(fields):
             """

tests/migrations/test_autodetector.py

@@ -24,6 +24,8 @@ class AutodetectorTests(TestCase):
     author_with_custom_user = ModelState("testapp", "Author", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=200)), ("user", models.ForeignKey("thirdapp.CustomUser"))])
     author_proxy = ModelState("testapp", "AuthorProxy", [], {"proxy": True}, ("testapp.author", ))
     author_proxy_notproxy = ModelState("testapp", "AuthorProxy", [], {}, ("testapp.author", ))
+    author_unmanaged = ModelState("testapp", "AuthorUnmanaged", [], {"managed": False}, ("testapp.author", ))
+    author_unmanaged_managed = ModelState("testapp", "AuthorUnmanaged", [], {}, ("testapp.author", ))
     publisher = ModelState("testapp", "Publisher", [("id", models.AutoField(primary_key=True)), ("name", models.CharField(max_length=100))])
     publisher_with_author = ModelState("testapp", "Publisher", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("testapp.Author")), ("name", models.CharField(max_length=100))])
     publisher_with_book = ModelState("testapp", "Publisher", [("id", models.AutoField(primary_key=True)), ("author", models.ForeignKey("otherapp.Book")), ("name", models.CharField(max_length=100))])
@@ -488,6 +490,31 @@ def test_proxy_ignorance(self):
         self.assertEqual(action.__class__.__name__, "CreateModel")
         self.assertEqual(action.name, "AuthorProxy")
 
+    def test_unmanaged_ignorance(self):
+        "Tests that the autodetector correctly ignores managed models"
+        # First, we test adding an unmanaged model
+        before = self.make_project_state([self.author_empty])
+        after = self.make_project_state([self.author_empty, self.author_unmanaged])
+        autodetector = MigrationAutodetector(before, after)
+        changes = autodetector._detect_changes()
+        # Right number of migrations?
+        self.assertEqual(len(changes), 0)
+
+        # Now, we test turning an unmanaged model into a managed model
+        before = self.make_project_state([self.author_empty, self.author_unmanaged])
+        after = self.make_project_state([self.author_empty, self.author_unmanaged_managed])
+        autodetector = MigrationAutodetector(before, after)
+        changes = autodetector._detect_changes()
+        # Right number of migrations?
+        self.assertEqual(len(changes['testapp']), 1)
+        # Right number of actions?
+        migration = changes['testapp'][0]
+        self.assertEqual(len(migration.operations), 1)
+        # Right action?
+        action = migration.operations[0]
+        self.assertEqual(action.__class__.__name__, "CreateModel")
+        self.assertEqual(action.name, "AuthorUnmanaged")
+
     @override_settings(AUTH_USER_MODEL="thirdapp.CustomUser")
     def test_swappable(self):
         before = self.make_project_state([self.custom_user])