Fixed #23121: AlterModelOptions operation not changing state right

4 files changed, 45 insertions, 18 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index dfbfe869fd..e27d8ace74 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -10,6 +10,7 @@ from django.db.migrations import operations
 from django.db.migrations.migration import Migration
 from django.db.migrations.questioner import MigrationQuestioner
 from django.db.migrations.optimizer import MigrationOptimizer
+from django.db.migrations.operations.models import AlterModelOptions
 
 
 class MigrationAutodetector(object):
@@ -25,17 +26,6 @@ class MigrationAutodetector(object):
     if it wishes, with the caveat that it may not always be possible.
     """
 
-    # Model options we want to compare and preserve in an AlterModelOptions op
-    ALTER_OPTION_KEYS = [
-        "get_latest_by",
-        "ordering",
-        "permissions",
-        "default_permissions",
-        "select_on_save",
-        "verbose_name",
-        "verbose_name_plural",
-    ]
-
     def __init__(self, from_state, to_state, questioner=None):
         self.from_state = from_state
         self.to_state = to_state
@@ -864,11 +854,11 @@ class MigrationAutodetector(object):
             new_model_state = self.to_state.models[app_label, model_name]
             old_options = dict(
                 option for option in old_model_state.options.items()
-                if option[0] in self.ALTER_OPTION_KEYS
+                if option[0] in AlterModelOptions.ALTER_OPTION_KEYS
             )
             new_options = dict(
                 option for option in new_model_state.options.items()
-                if option[0] in self.ALTER_OPTION_KEYS
+                if option[0] in AlterModelOptions.ALTER_OPTION_KEYS
             )
             if old_options != new_options:
                 self.add_operation(
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 1ded7c6db4..4e8100a5bb 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -337,6 +337,17 @@ class AlterModelOptions(Operation):
     may still need them.
     """
 
+    # Model options we want to compare and preserve in an AlterModelOptions op
+    ALTER_OPTION_KEYS = [
+        "get_latest_by",
+        "ordering",
+        "permissions",
+        "default_permissions",
+        "select_on_save",
+        "verbose_name",
+        "verbose_name_plural",
+    ]
+
     def __init__(self, name, options):
         self.name = name
         self.options = options
@@ -345,6 +356,9 @@ class AlterModelOptions(Operation):
         model_state = state.models[app_label, self.name.lower()]
         model_state.options = dict(model_state.options)
         model_state.options.update(self.options)
+        for key in self.ALTER_OPTION_KEYS:
+            if key not in self.options and key in model_state.options:
+                del model_state.options[key]
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         pass
diff --git a/tests/migrations/test_autodetector.py b/tests/migrations/test_autodetector.py
index 8b13269d77..e750fc9194 100644
--- a/tests/migrations/test_autodetector.py
+++ b/tests/migrations/test_autodetector.py
@@ -897,6 +897,13 @@ class AutodetectorTests(TestCase):
         self.assertNumberMigrations(changes, "testapp", 1)
         # Right actions in right order?
         self.assertOperationTypes(changes, "testapp", 0, ["AlterModelOptions"])
+        # Changing them back to empty should also make a change
+        before = self.make_project_state([self.author_with_options])
+        after = self.make_project_state([self.author_empty])
+        autodetector = MigrationAutodetector(before, after)
+        changes = autodetector._detect_changes()
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(changes, "testapp", 0, ["AlterModelOptions"])
 
     def test_alter_model_options_proxy(self):
         """
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index 815838d826..769d0be417 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -46,7 +46,7 @@ class OperationTestBase(MigrationTestBase):
         operation.state_forwards(app_label, new_state)
         return project_state, new_state
 
-    def set_up_test_model(self, app_label, second_model=False, third_model=False, related_model=False, mti_model=False, proxy_model=False, unique_together=False):
+    def set_up_test_model(self, app_label, second_model=False, third_model=False, related_model=False, mti_model=False, proxy_model=False, unique_together=False, options=False):
         """
         Creates a test model state and database table.
         """
@@ -76,6 +76,12 @@ class OperationTestBase(MigrationTestBase):
             except DatabaseError:
                 pass
         # Make the "current" state
+        model_options = {
+            "swappable": "TEST_SWAP_MODEL",
+            "unique_together": [["pink", "weight"]] if unique_together else [],
+        }
+        if options:
+            model_options["permissions"] = [("can_groom", "Can groom")]
         operations = [migrations.CreateModel(
             "Pony",
             [
@@ -83,10 +89,7 @@ class OperationTestBase(MigrationTestBase):
                 ("pink", models.IntegerField(default=3)),
                 ("weight", models.FloatField()),
             ],
-            options={
-                "swappable": "TEST_SWAP_MODEL",
-                "unique_together": [["pink", "weight"]] if unique_together else [],
-            },
+            options=model_options,
         )]
         if second_model:
             operations.append(migrations.CreateModel(
@@ -975,6 +978,19 @@ class OperationTests(OperationTestBase):
         self.assertEqual(len(new_state.models["test_almoop", "pony"].options.get("permissions", [])), 1)
         self.assertEqual(new_state.models["test_almoop", "pony"].options["permissions"][0][0], "can_groom")
 
+    def test_alter_model_options_emptying(self):
+        """
+        Tests that the AlterModelOptions operation removes keys from the dict (#23121)
+        """
+        project_state = self.set_up_test_model("test_almoop", options=True)
+        # Test the state alteration (no DB alteration to test)
+        operation = migrations.AlterModelOptions("Pony", {})
+        self.assertEqual(operation.describe(), "Change Meta options on Pony")
+        new_state = project_state.clone()
+        operation.state_forwards("test_almoop", new_state)
+        self.assertEqual(len(project_state.models["test_almoop", "pony"].options.get("permissions", [])), 1)
+        self.assertEqual(len(new_state.models["test_almoop", "pony"].options.get("permissions", [])), 0)
+
     def test_alter_order_with_respect_to(self):
         """
         Tests the AlterOrderWithRespectTo operation.