Fixed #23822 -- Added support for serializing model managers in migration

Thanks to Shai Berger, Loïc Bistuer, Simon Charette, Andrew Godwin,
Tim Graham, Carl Meyer, and others for their review and input.

tests/migrations/test_state.py

@@ -3,7 +3,8 @@ from django.db import models
 from django.db.migrations.state import ProjectState, ModelState, InvalidBasesError
 from django.test import TestCase
 
-from .models import ModelWithCustomBase
+from .models import (FoodManager, FoodQuerySet, ModelWithCustomBase,
+    NoMigrationFoodManager)
 
 
 class StateTests(TestCase):
@@ -54,11 +55,56 @@ class StateTests(TestCase):
                 verbose_name = "tome"
                 db_table = "test_tome"
 
+        class Food(models.Model):
+
+            food_mgr = FoodManager('a', 'b')
+            food_qs = FoodQuerySet.as_manager()
+            food_no_mgr = NoMigrationFoodManager('x', 'y')
+
+            class Meta:
+                app_label = "migrations"
+                apps = new_apps
+
+        class FoodNoManagers(models.Model):
+
+            class Meta:
+                app_label = "migrations"
+                apps = new_apps
+
+        class FoodNoDefaultManager(models.Model):
+
+            food_no_mgr = NoMigrationFoodManager('x', 'y')
+            food_mgr = FoodManager('a', 'b')
+            food_qs = FoodQuerySet.as_manager()
+
+            class Meta:
+                app_label = "migrations"
+                apps = new_apps
+
+        mgr1 = FoodManager('a', 'b')
+        mgr2 = FoodManager('x', 'y', c=3, d=4)
+
+        class FoodOrderedManagers(models.Model):
+            # The managers on this model should be orderd by their creation
+            # counter and not by the order in model body
+
+            food_no_mgr = NoMigrationFoodManager('x', 'y')
+            food_mgr2 = mgr2
+            food_mgr1 = mgr1
+
+            class Meta:
+                app_label = "migrations"
+                apps = new_apps
+
         project_state = ProjectState.from_apps(new_apps)
         author_state = project_state.models['migrations', 'author']
         author_proxy_state = project_state.models['migrations', 'authorproxy']
         sub_author_state = project_state.models['migrations', 'subauthor']
         book_state = project_state.models['migrations', 'book']
+        food_state = project_state.models['migrations', 'food']
+        food_no_managers_state = project_state.models['migrations', 'foodnomanagers']
+        food_no_default_manager_state = project_state.models['migrations', 'foodnodefaultmanager']
+        food_order_manager_state = project_state.models['migrations', 'foodorderedmanagers']
 
         self.assertEqual(author_state.app_label, "migrations")
         self.assertEqual(author_state.name, "Author")
@@ -89,26 +135,43 @@ class StateTests(TestCase):
         self.assertEqual(len(sub_author_state.fields), 2)
         self.assertEqual(sub_author_state.bases, ("migrations.author", ))
 
+        # The default manager is used in migrations
+        self.assertEqual([name for name, mgr in food_state.managers], ['food_mgr'])
+        self.assertEqual(food_state.managers[0][1].args, ('a', 'b', 1, 2))
+
+        # No explicit managers defined. Migrations will fall back to the default
+        self.assertEqual(food_no_managers_state.managers, [])
+
+        # food_mgr is used in migration but isn't the default mgr, hence add the
+        # default
+        self.assertEqual([name for name, mgr in food_no_default_manager_state.managers],
+                         ['food_no_mgr', 'food_mgr'])
+        self.assertEqual(food_no_default_manager_state.managers[0][1].__class__, models.Manager)
+        self.assertIsInstance(food_no_default_manager_state.managers[1][1], FoodManager)
+
+        self.assertEqual([name for name, mgr in food_order_manager_state.managers],
+                         ['food_mgr1', 'food_mgr2'])
+        self.assertEqual([mgr.args for name, mgr in food_order_manager_state.managers],
+                         [('a', 'b', 1, 2), ('x', 'y', 3, 4)])
+
     def test_render(self):
         """
         Tests rendering a ProjectState into an Apps.
         """
         project_state = ProjectState()
         project_state.add_model_state(ModelState(
-            "migrations",
-            "Tag",
-            [
+            app_label="migrations",
+            name="Tag",
+            fields=[
                 ("id", models.AutoField(primary_key=True)),
                 ("name", models.CharField(max_length=100)),
                 ("hidden", models.BooleanField()),
             ],
-            {},
-            None,
         ))
         project_state.add_model_state(ModelState(
-            "migrations",
-            "SubTag",
-            [
+            app_label="migrations",
+            name="SubTag",
+            fields=[
                 ('tag_ptr', models.OneToOneField(
                     auto_created=True,
                     primary_key=True,
@@ -118,15 +181,40 @@ class StateTests(TestCase):
                 )),
                 ("awesome", models.BooleanField()),
             ],
-            options={},
             bases=("migrations.Tag",),
         ))
 
+        base_mgr = models.Manager()
+        mgr1 = FoodManager('a', 'b')
+        mgr2 = FoodManager('x', 'y', c=3, d=4)
+        project_state.add_model_state(ModelState(
+            app_label="migrations",
+            name="Food",
+            fields=[
+                ("id", models.AutoField(primary_key=True)),
+            ],
+            managers=[
+                # The ordering we really want is objects, mgr1, mgr2
+                ('default', base_mgr),
+                ('food_mgr2', mgr2),
+                ('food_mgr1', mgr1),
+            ]
+        ))
+
         new_apps = project_state.render()
         self.assertEqual(new_apps.get_model("migrations", "Tag")._meta.get_field_by_name("name")[0].max_length, 100)
         self.assertEqual(new_apps.get_model("migrations", "Tag")._meta.get_field_by_name("hidden")[0].null, False)
+
         self.assertEqual(len(new_apps.get_model("migrations", "SubTag")._meta.local_fields), 2)
 
+        Food = new_apps.get_model("migrations", "Food")
+        managers = sorted(Food._meta.managers)
+        self.assertEqual([mgr.name for _, mgr, _ in managers],
+                         ['default', 'food_mgr1', 'food_mgr2'])
+        self.assertEqual([mgr.__class__ for _, mgr, _ in managers],
+                         [models.Manager, FoodManager, FoodManager])
+        self.assertIs(managers[0][1], Food._default_manager)
+
     def test_render_model_inheritance(self):
         class Book(models.Model):
             title = models.CharField(max_length=1000)