Replaced migration state render() by apps cached property

Refs #23745.

9 files changed, 140 insertions, 162 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index 440b83880c..d96f09b0be 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -108,8 +108,8 @@ class MigrationAutodetector(object):
 
         # Prepare some old/new state and model lists, separating
         # proxy models and ignoring unmigrated apps.
-        self.old_apps = self.from_state.render(ignore_swappable=True)
-        self.new_apps = self.to_state.render()
+        self.old_apps = self.from_state.apps
+        self.new_apps = self.to_state.apps
         self.old_model_keys = []
         self.old_proxy_keys = []
         self.old_unmanaged_keys = []
diff --git a/django/db/migrations/executor.py b/django/db/migrations/executor.py
index f5811bb795..4a73546ba8 100644
--- a/django/db/migrations/executor.py
+++ b/django/db/migrations/executor.py
@@ -137,7 +137,7 @@ class MigrationExecutor(object):
         on initial migrations (as it only looks for CreateModel).
         """
         project_state = self.loader.project_state((migration.app_label, migration.name), at_end=True)
-        apps = project_state.render()
+        apps = project_state.apps
         found_create_migration = False
         # Bail if the migration isn't the first one in its app
         if [name for app, name in migration.dependencies if app == migration.app_label]:
diff --git a/django/db/migrations/operations/fields.py b/django/db/migrations/operations/fields.py
index fd3f62de1f..ba123de9c3 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -40,9 +40,9 @@ class AddField(Operation):
         state.models[app_label, self.model_name.lower()].fields.append((self.name, field))
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.model_name)
+        to_model = to_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.model_name)
+            from_model = from_state.apps.get_model(app_label, self.model_name)
             field = to_model._meta.get_field_by_name(self.name)[0]
             if not self.preserve_default:
                 field.default = self.field.default
@@ -54,7 +54,7 @@ class AddField(Operation):
                 field.default = NOT_PROVIDED
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        from_model = from_state.render().get_model(app_label, self.model_name)
+        from_model = from_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, from_model):
             schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
 
@@ -96,14 +96,14 @@ class RemoveField(Operation):
         state.models[app_label, self.model_name.lower()].fields = new_fields
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        from_model = from_state.render().get_model(app_label, self.model_name)
+        from_model = from_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, from_model):
             schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.model_name)
+        to_model = to_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.model_name)
+            from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.add_field(from_model, to_model._meta.get_field_by_name(self.name)[0])
 
     def describe(self):
@@ -152,9 +152,9 @@ class AlterField(Operation):
         ]
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.model_name)
+        to_model = to_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.model_name)
+            from_model = from_state.apps.get_model(app_label, self.model_name)
             from_field = from_model._meta.get_field_by_name(self.name)[0]
             to_field = to_model._meta.get_field_by_name(self.name)[0]
             # If the field is a relatedfield with an unresolved rel.to, just
@@ -222,9 +222,9 @@ class RenameField(Operation):
                 ]
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.model_name)
+        to_model = to_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.model_name)
+            from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.alter_field(
                 from_model,
                 from_model._meta.get_field_by_name(self.old_name)[0],
@@ -232,9 +232,9 @@ class RenameField(Operation):
             )
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.model_name)
+        to_model = to_state.apps.get_model(app_label, self.model_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.model_name)
+            from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.alter_field(
                 from_model,
                 from_model._meta.get_field_by_name(self.new_name)[0],
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 2436701919..eda30f88e8 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -49,14 +49,12 @@ class CreateModel(Operation):
         )
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        apps = to_state.render()
-        model = apps.get_model(app_label, self.name)
+        model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, model):
             schema_editor.create_model(model)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        apps = from_state.render()
-        model = apps.get_model(app_label, self.name)
+        model = from_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, model):
             schema_editor.delete_model(model)
 
@@ -103,14 +101,12 @@ class DeleteModel(Operation):
         del state.models[app_label, self.name.lower()]
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        apps = from_state.render()
-        model = apps.get_model(app_label, self.name)
+        model = from_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, model):
             schema_editor.delete_model(model)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        apps = to_state.render()
-        model = apps.get_model(app_label, self.name)
+        model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, model):
             schema_editor.create_model(model)
 
@@ -143,7 +139,7 @@ class RenameModel(Operation):
 
     def state_forwards(self, app_label, state):
         # Get all of the related objects we need to repoint
-        apps = state.render(skip_cache=True)
+        apps = state.apps
         model = apps.get_model(app_label, self.old_name)
         related_objects = model._meta.get_all_related_objects()
         related_m2m_objects = model._meta.get_all_related_many_to_many_objects()
@@ -168,13 +164,12 @@ class RenameModel(Operation):
                     field.rel.to = "%s.%s" % (app_label, self.new_name)
                 new_fields.append((name, field))
             state.models[related_key].fields = new_fields
+        del state.apps  # FIXME: this should be replaced by a logic in state (update_model?)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        new_apps = to_state.render()
-        new_model = new_apps.get_model(app_label, self.new_name)
+        new_model = to_state.apps.get_model(app_label, self.new_name)
         if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
-            old_apps = from_state.render()
-            old_model = old_apps.get_model(app_label, self.old_name)
+            old_model = from_state.apps.get_model(app_label, self.old_name)
             # Move the main table
             schema_editor.alter_db_table(
                 new_model,
@@ -194,7 +189,7 @@ class RenameModel(Operation):
                         related_object.model._meta.app_label,
                         related_object.model._meta.object_name.lower(),
                     )
-                to_field = new_apps.get_model(
+                to_field = to_state.apps.get_model(
                     *related_key
                 )._meta.get_field_by_name(related_object.field.name)[0]
                 schema_editor.alter_field(
@@ -242,11 +237,9 @@ class AlterModelTable(Operation):
         state.models[app_label, self.name.lower()].options["db_table"] = self.table
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        new_apps = to_state.render()
-        new_model = new_apps.get_model(app_label, self.name)
+        new_model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
-            old_apps = from_state.render()
-            old_model = old_apps.get_model(app_label, self.name)
+            old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_db_table(
                 new_model,
                 old_model._meta.db_table,
@@ -299,11 +292,9 @@ class AlterUniqueTogether(Operation):
         model_state.options[self.option_name] = self.unique_together
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        new_apps = to_state.render()
-        new_model = new_apps.get_model(app_label, self.name)
+        new_model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
-            old_apps = from_state.render()
-            old_model = old_apps.get_model(app_label, self.name)
+            old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_unique_together(
                 new_model,
                 getattr(old_model._meta, self.option_name, set()),
@@ -348,11 +339,9 @@ class AlterIndexTogether(Operation):
         model_state.options[self.option_name] = self.index_together
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        new_apps = to_state.render()
-        new_model = new_apps.get_model(app_label, self.name)
+        new_model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
-            old_apps = from_state.render()
-            old_model = old_apps.get_model(app_label, self.name)
+            old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_index_together(
                 new_model,
                 getattr(old_model._meta, self.option_name, set()),
@@ -394,9 +383,9 @@ class AlterOrderWithRespectTo(Operation):
         model_state.options['order_with_respect_to'] = self.order_with_respect_to
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        to_model = to_state.render().get_model(app_label, self.name)
+        to_model = to_state.apps.get_model(app_label, self.name)
         if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
-            from_model = from_state.render().get_model(app_label, self.name)
+            from_model = from_state.apps.get_model(app_label, self.name)
             # Remove a field if we need to
             if from_model._meta.order_with_respect_to and not to_model._meta.order_with_respect_to:
                 schema_editor.remove_field(from_model, from_model._meta.get_field_by_name("_order")[0])
diff --git a/django/db/migrations/operations/special.py b/django/db/migrations/operations/special.py
index c7d438c2a0..96fd2cc63c 100644
--- a/django/db/migrations/operations/special.py
+++ b/django/db/migrations/operations/special.py
@@ -166,12 +166,12 @@ class RunPython(Operation):
         # object, representing the versioned models as an app registry.
         # We could try to override the global cache, but then people will still
         # use direct imports, so we go with a documentation approach instead.
-        self.code(from_state.render(), schema_editor)
+        self.code(from_state.apps, schema_editor)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         if self.reverse_code is None:
             raise NotImplementedError("You cannot reverse this operation")
-        self.reverse_code(from_state.render(), schema_editor)
+        self.reverse_code(from_state.apps, schema_editor)
 
     def describe(self):
         return "Raw Python operation"
diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 871e9920fa..f2267b3536 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -9,6 +9,7 @@ from django.db.models.fields.proxy import OrderWrt
 from django.conf import settings
 from django.utils import six
 from django.utils.encoding import force_text, smart_text
+from django.utils.functional import cached_property
 from django.utils.module_loading import import_string
 from django.utils.version import get_docs_version
 
@@ -26,7 +27,6 @@ class ProjectState(object):
 
     def __init__(self, models=None, real_apps=None):
         self.models = models or {}
-        self.apps = None
         # Apps to include from main registry, usually unmigrated ones
         self.real_apps = real_apps or []
 
@@ -40,66 +40,9 @@ class ProjectState(object):
             real_apps=self.real_apps,
         )
 
-    def render(self, include_real=None, ignore_swappable=False, skip_cache=False):
-        "Turns the project state into actual models in a new Apps"
-        if self.apps is None or skip_cache:
-            # Any apps in self.real_apps should have all their models included
-            # in the render. We don't use the original model instances as there
-            # are some variables that refer to the Apps object.
-            # FKs/M2Ms from real apps are also not included as they just
-            # mess things up with partial states (due to lack of dependencies)
-            real_models = []
-            for app_label in self.real_apps:
-                app = global_apps.get_app_config(app_label)
-                for model in app.get_models():
-                    real_models.append(ModelState.from_model(model, exclude_rels=True))
-            # Populate the app registry with a stub for each application.
-            app_labels = set(model_state.app_label for model_state in self.models.values())
-            self.apps = Apps([AppConfigStub(label) for label in sorted(self.real_apps + list(app_labels))])
-            # We keep trying to render the models in a loop, ignoring invalid
-            # base errors, until the size of the unrendered models doesn't
-            # decrease by at least one, meaning there's a base dependency loop/
-            # missing base.
-            unrendered_models = list(self.models.values()) + real_models
-            while unrendered_models:
-                new_unrendered_models = []
-                for model in unrendered_models:
-                    try:
-                        model.render(self.apps)
-                    except InvalidBasesError:
-                        new_unrendered_models.append(model)
-                if len(new_unrendered_models) == len(unrendered_models):
-                    raise InvalidBasesError(
-                        "Cannot resolve bases for %r\nThis can happen if you are inheriting models from an "
-                        "app with migrations (e.g. contrib.auth)\n in an app with no migrations; see "
-                        "https://docs.djangoproject.com/en/%s/topics/migrations/#dependencies "
-                        "for more" % (new_unrendered_models, get_docs_version())
-                    )
-                unrendered_models = new_unrendered_models
-            # make sure apps has no dangling references
-            if self.apps._pending_lookups:
-                # There's some lookups left. See if we can first resolve them
-                # ourselves - sometimes fields are added after class_prepared is sent
-                for lookup_model, operations in self.apps._pending_lookups.items():
-                    try:
-                        model = self.apps.get_model(lookup_model[0], lookup_model[1])
-                    except LookupError:
-                        app_label = "%s.%s" % (lookup_model[0], lookup_model[1])
-                        if app_label == settings.AUTH_USER_MODEL and ignore_swappable:
-                            continue
-                        # Raise an error with a best-effort helpful message
-                        # (only for the first issue). Error message should look like:
-                        # "ValueError: Lookup failed for model referenced by
-                        # field migrations.Book.author: migrations.Author"
-                        msg = "Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}"
-                        raise ValueError(msg.format(field=operations[0][1], model=lookup_model))
-                    else:
-                        do_pending_lookups(model)
-        try:
-            return self.apps
-        finally:
-            if skip_cache:
-                self.apps = None
+    @cached_property
+    def apps(self):
+        return StateApps(self.real_apps, self.models)
 
     @classmethod
     def from_apps(cls, apps):
@@ -139,6 +82,67 @@ class AppConfigStub(AppConfig):
         self.models = all_models
 
 
+class StateApps(Apps):
+    """
+    Subclass of the global Apps registry class to better handle dynamic model
+    additions and removals.
+    """
+    def __init__(self, real_apps, models):
+        # Any apps in self.real_apps should have all their models included
+        # in the render. We don't use the original model instances as there
+        # are some variables that refer to the Apps object.
+        # FKs/M2Ms from real apps are also not included as they just
+        # mess things up with partial states (due to lack of dependencies)
+        real_models = []
+        for app_label in real_apps:
+            app = global_apps.get_app_config(app_label)
+            for model in app.get_models():
+                real_models.append(ModelState.from_model(model, exclude_rels=True))
+        # Populate the app registry with a stub for each application.
+        app_labels = {model_state.app_label for model_state in models.values()}
+        app_configs = [AppConfigStub(label) for label in sorted(real_apps + list(app_labels))]
+        super(StateApps, self).__init__(app_configs)
+
+        # We keep trying to render the models in a loop, ignoring invalid
+        # base errors, until the size of the unrendered models doesn't
+        # decrease by at least one, meaning there's a base dependency loop/
+        # missing base.
+        unrendered_models = list(models.values()) + real_models
+        while unrendered_models:
+            new_unrendered_models = []
+            for model in unrendered_models:
+                try:
+                    model.render(self)
+                except InvalidBasesError:
+                    new_unrendered_models.append(model)
+            if len(new_unrendered_models) == len(unrendered_models):
+                raise InvalidBasesError(
+                    "Cannot resolve bases for %r\nThis can happen if you are inheriting models from an "
+                    "app with migrations (e.g. contrib.auth)\n in an app with no migrations; see "
+                    "https://docs.djangoproject.com/en/%s/topics/migrations/#dependencies "
+                    "for more" % (new_unrendered_models, get_docs_version())
+                )
+            unrendered_models = new_unrendered_models
+
+        # If there are some lookups left, see if we can first resolve them
+        # ourselves - sometimes fields are added after class_prepared is sent
+        for lookup_model, operations in self._pending_lookups.items():
+            try:
+                model = self.get_model(lookup_model[0], lookup_model[1])
+            except LookupError:
+                app_label = "%s.%s" % (lookup_model[0], lookup_model[1])
+                if app_label == settings.AUTH_USER_MODEL and ignore_swappable:
+                    continue
+                # Raise an error with a best-effort helpful message
+                # (only for the first issue). Error message should look like:
+                # "ValueError: Lookup failed for model referenced by
+                # field migrations.Book.author: migrations.Author"
+                msg = "Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}"
+                raise ValueError(msg.format(field=operations[0][1], model=lookup_model))
+            else:
+                do_pending_lookups(model)
+
+
 class ModelState(object):
     """
     Represents a Django Model. We don't use the actual Model class
diff --git a/tests/migrations/test_executor.py b/tests/migrations/test_executor.py
index 1bc1ca781d..d21dc69472 100644
--- a/tests/migrations/test_executor.py
+++ b/tests/migrations/test_executor.py
@@ -219,7 +219,7 @@ class ExecutorTests(MigrationTestBase):
         # exists in the global app registry temporarily.
         old_table_names = connection.introspection.table_names
         connection.introspection.table_names = lambda c: [x for x in old_table_names(c) if x != "auth_user"]
-        migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).render()
+        migrations_apps = executor.loader.project_state(("migrations", "0001_initial")).apps
         global_apps.get_app_config("migrations").models["author"] = migrations_apps.get_model("migrations", "author")
         try:
             migration = executor.loader.get_migration("auth", "0001_initial")
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index fa2965a3f8..b52a4df585 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -267,9 +267,8 @@ class OperationTests(OperationTestBase):
         self.assertColumnNotExists("test_crmomm_stable", "ponies")
         # Make sure the M2M field actually works
         with atomic():
-            new_apps = new_state.render()
-            Pony = new_apps.get_model("test_crmomm", "Pony")
-            Stable = new_apps.get_model("test_crmomm", "Stable")
+            Pony = new_state.apps.get_model("test_crmomm", "Pony")
+            Stable = new_state.apps.get_model("test_crmomm", "Stable")
             stable = Stable.objects.create()
             p1 = Pony.objects.create(pink=False, weight=4.55)
             p2 = Pony.objects.create(pink=True, weight=5.43)
@@ -545,8 +544,7 @@ class OperationTests(OperationTestBase):
         project_state = self.apply_operations(app_label, project_state, operations=[
             migrations.RenameModel("ReflexivePony", "ReflexivePony2"),
         ])
-        apps = project_state.render()
-        Pony = apps.get_model(app_label, "ReflexivePony2")
+        Pony = project_state.apps.get_model(app_label, "ReflexivePony2")
         pony = Pony.objects.create()
         pony.ponies.add(pony)
 
@@ -589,8 +587,7 @@ class OperationTests(OperationTestBase):
         """
         project_state = self.set_up_test_model("test_adchfl")
 
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_adchfl", "Pony")
+        Pony = project_state.apps.get_model("test_adchfl", "Pony")
         pony = Pony.objects.create(weight=42)
 
         new_state = self.apply_operations("test_adchfl", project_state, [
@@ -618,8 +615,7 @@ class OperationTests(OperationTestBase):
             ),
         ])
 
-        new_apps = new_state.render()
-        Pony = new_apps.get_model("test_adchfl", "Pony")
+        Pony = new_state.apps.get_model("test_adchfl", "Pony")
         pony = Pony.objects.get(pk=pony.pk)
         self.assertEqual(pony.text, "some text")
         self.assertEqual(pony.empty, "")
@@ -632,8 +628,7 @@ class OperationTests(OperationTestBase):
         """
         project_state = self.set_up_test_model("test_adtxtfl")
 
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_adtxtfl", "Pony")
+        Pony = project_state.apps.get_model("test_adtxtfl", "Pony")
         pony = Pony.objects.create(weight=42)
 
         new_state = self.apply_operations("test_adtxtfl", project_state, [
@@ -661,8 +656,7 @@ class OperationTests(OperationTestBase):
             ),
         ])
 
-        new_apps = new_state.render()
-        Pony = new_apps.get_model("test_adtxtfl", "Pony")
+        Pony = new_state.apps.get_model("test_adtxtfl", "Pony")
         pony = Pony.objects.get(pk=pony.pk)
         self.assertEqual(pony.text, "some text")
         self.assertEqual(pony.empty, "")
@@ -676,8 +670,7 @@ class OperationTests(OperationTestBase):
         """
         project_state = self.set_up_test_model("test_adbinfl")
 
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_adbinfl", "Pony")
+        Pony = project_state.apps.get_model("test_adbinfl", "Pony")
         pony = Pony.objects.create(weight=42)
 
         new_state = self.apply_operations("test_adbinfl", project_state, [
@@ -705,8 +698,7 @@ class OperationTests(OperationTestBase):
             ),
         ])
 
-        new_apps = new_state.render()
-        Pony = new_apps.get_model("test_adbinfl", "Pony")
+        Pony = new_state.apps.get_model("test_adbinfl", "Pony")
         pony = Pony.objects.get(pk=pony.pk)
         # SQLite returns buffer/memoryview, cast to bytes for checking.
         self.assertEqual(bytes(pony.blob), b"some text")
@@ -753,7 +745,7 @@ class OperationTests(OperationTestBase):
         ][0]
         self.assertEqual(field.default, NOT_PROVIDED)
         # Test the database alteration
-        project_state.render().get_model("test_adflpd", "pony").objects.create(
+        project_state.apps.get_model("test_adflpd", "pony").objects.create(
             weight=4,
         )
         self.assertColumnNotExists("test_adflpd_pony", "height")
@@ -784,8 +776,7 @@ class OperationTests(OperationTestBase):
         self.assertColumnNotExists("test_adflmm_pony", "stables")
         # Make sure the M2M field actually works
         with atomic():
-            new_apps = new_state.render()
-            Pony = new_apps.get_model("test_adflmm", "Pony")
+            Pony = new_state.apps.get_model("test_adflmm", "Pony")
             p = Pony.objects.create(pink=False, weight=4.55)
             p.stables.create()
             self.assertEqual(p.stables.count(), 1)
@@ -801,15 +792,13 @@ class OperationTests(OperationTestBase):
         project_state = self.apply_operations("test_alflmm", project_state, operations=[
             migrations.AddField("Pony", "stables", models.ManyToManyField("Stable", related_name="ponies"))
         ])
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_alflmm", "Pony")
+        Pony = project_state.apps.get_model("test_alflmm", "Pony")
         self.assertFalse(Pony._meta.get_field('stables').blank)
 
         project_state = self.apply_operations("test_alflmm", project_state, operations=[
             migrations.AlterField("Pony", "stables", models.ManyToManyField(to="Stable", related_name="ponies", blank=True))
         ])
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_alflmm", "Pony")
+        Pony = project_state.apps.get_model("test_alflmm", "Pony")
         self.assertTrue(Pony._meta.get_field('stables').blank)
 
     def test_repoint_field_m2m(self):
@@ -818,16 +807,14 @@ class OperationTests(OperationTestBase):
         project_state = self.apply_operations("test_alflmm", project_state, operations=[
             migrations.AddField("Pony", "places", models.ManyToManyField("Stable", related_name="ponies"))
         ])
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_alflmm", "Pony")
+        Pony = project_state.apps.get_model("test_alflmm", "Pony")
 
         project_state = self.apply_operations("test_alflmm", project_state, operations=[
             migrations.AlterField("Pony", "places", models.ManyToManyField(to="Van", related_name="ponies"))
         ])
 
         # Ensure the new field actually works
-        new_apps = project_state.render()
-        Pony = new_apps.get_model("test_alflmm", "Pony")
+        Pony = project_state.apps.get_model("test_alflmm", "Pony")
         p = Pony.objects.create(pink=False, weight=4.55)
         p.places.create()
         self.assertEqual(p.places.count(), 1)
@@ -1238,7 +1225,7 @@ class OperationTests(OperationTestBase):
         # Make sure there's no matching index
         self.assertColumnNotExists("test_alorwrtto_rider", "_order")
         # Create some rows before alteration
-        rendered_state = project_state.render()
+        rendered_state = project_state.apps
         pony = rendered_state.get_model("test_alorwrtto", "Pony").objects.create(weight=50)
         rendered_state.get_model("test_alorwrtto", "Rider").objects.create(pony=pony, friend_id=1)
         rendered_state.get_model("test_alorwrtto", "Rider").objects.create(pony=pony, friend_id=2)
@@ -1247,7 +1234,7 @@ class OperationTests(OperationTestBase):
             operation.database_forwards("test_alorwrtto", editor, project_state, new_state)
         self.assertColumnExists("test_alorwrtto_rider", "_order")
         # Check for correct value in rows
-        updated_riders = new_state.render().get_model("test_alorwrtto", "Rider").objects.all()
+        updated_riders = new_state.apps.get_model("test_alorwrtto", "Rider").objects.all()
         self.assertEqual(updated_riders[0]._order, 0)
         self.assertEqual(updated_riders[1]._order, 0)
         # And test reversal
@@ -1530,15 +1517,15 @@ class OperationTests(OperationTestBase):
         operation.state_forwards("test_runpython", new_state)
         self.assertEqual(new_state, project_state)
         # Test the database alteration
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 0)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 0)
         with connection.schema_editor() as editor:
             operation.database_forwards("test_runpython", editor, project_state, new_state)
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 2)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 2)
         # Now test reversal
         self.assertTrue(operation.reversible)
         with connection.schema_editor() as editor:
             operation.database_backwards("test_runpython", editor, project_state, new_state)
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 0)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 0)
         # Now test we can't use a string
         with self.assertRaises(ValueError):
             migrations.RunPython("print 'ahahaha'")
@@ -1555,7 +1542,7 @@ class OperationTests(OperationTestBase):
             no_reverse_operation.database_forwards("test_runpython", editor, project_state, new_state)
             with self.assertRaises(NotImplementedError):
                 no_reverse_operation.database_backwards("test_runpython", editor, new_state, project_state)
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 2)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 2)
 
         def create_ponies(models, schema_editor):
             Pony = models.get_model("test_runpython", "Pony")
@@ -1568,7 +1555,7 @@ class OperationTests(OperationTestBase):
         operation = migrations.RunPython(create_ponies)
         with connection.schema_editor() as editor:
             operation.database_forwards("test_runpython", editor, project_state, new_state)
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 4)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 4)
         # And deconstruction
         definition = operation.deconstruct()
         self.assertEqual(definition[0], "RunPython")
@@ -1586,8 +1573,8 @@ class OperationTests(OperationTestBase):
         operation = migrations.RunPython(create_shetlandponies)
         with connection.schema_editor() as editor:
             operation.database_forwards("test_runpython", editor, project_state, new_state)
-        self.assertEqual(project_state.render().get_model("test_runpython", "Pony").objects.count(), 6)
-        self.assertEqual(project_state.render().get_model("test_runpython", "ShetlandPony").objects.count(), 2)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "Pony").objects.count(), 6)
+        self.assertEqual(project_state.apps.get_model("test_runpython", "ShetlandPony").objects.count(), 2)
 
     def test_run_python_atomic(self):
         """
@@ -1606,26 +1593,26 @@ class OperationTests(OperationTestBase):
         non_atomic_migration.operations = [migrations.RunPython(inner_method, atomic=False)]
         # If we're a fully-transactional database, both versions should rollback
         if connection.features.can_rollback_ddl:
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 0)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 0)
             with self.assertRaises(ValueError):
                 with connection.schema_editor() as editor:
                     atomic_migration.apply(project_state, editor)
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 0)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 0)
             with self.assertRaises(ValueError):
                 with connection.schema_editor() as editor:
                     non_atomic_migration.apply(project_state, editor)
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 0)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 0)
         # Otherwise, the non-atomic operation should leave a row there
         else:
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 0)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 0)
             with self.assertRaises(ValueError):
                 with connection.schema_editor() as editor:
                     atomic_migration.apply(project_state, editor)
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 0)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 0)
             with self.assertRaises(ValueError):
                 with connection.schema_editor() as editor:
                     non_atomic_migration.apply(project_state, editor)
-            self.assertEqual(project_state.render().get_model("test_runpythonatomic", "Pony").objects.count(), 1)
+            self.assertEqual(project_state.apps.get_model("test_runpythonatomic", "Pony").objects.count(), 1)
         # And deconstruction
         definition = non_atomic_migration.operations[0].deconstruct()
         self.assertEqual(definition[0], "RunPython")
diff --git a/tests/migrations/test_state.py b/tests/migrations/test_state.py
index 512f75ec15..143ce49f8d 100644
--- a/tests/migrations/test_state.py
+++ b/tests/migrations/test_state.py
@@ -201,7 +201,7 @@ class StateTests(TestCase):
             ]
         ))
 
-        new_apps = project_state.render()
+        new_apps = project_state.apps
         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)
 
@@ -330,7 +330,7 @@ class StateTests(TestCase):
         project_state.add_model_state(ModelState.from_model(D))
         project_state.add_model_state(ModelState.from_model(E))
         project_state.add_model_state(ModelState.from_model(F))
-        final_apps = project_state.render()
+        final_apps = project_state.apps
         self.assertEqual(len(final_apps.get_models()), 6)
 
         # Now make an invalid ProjectState and make sure it fails
@@ -340,7 +340,7 @@ class StateTests(TestCase):
         project_state.add_model_state(ModelState.from_model(C))
         project_state.add_model_state(ModelState.from_model(F))
         with self.assertRaises(InvalidBasesError):
-            project_state.render()
+            project_state.apps
 
     def test_render_unique_app_labels(self):
         """
@@ -360,8 +360,7 @@ class StateTests(TestCase):
         project_state = ProjectState()
         project_state.add_model_state(ModelState.from_model(A))
         project_state.add_model_state(ModelState.from_model(B))
-        final_apps = project_state.render()
-        self.assertEqual(len(final_apps.get_models()), 2)
+        self.assertEqual(len(project_state.apps.get_models()), 2)
 
     def test_equality(self):
         """
@@ -432,20 +431,19 @@ class StateTests(TestCase):
         project_state.add_model_state(ModelState.from_model(Author))
         project_state.add_model_state(ModelState.from_model(Book))
         project_state.add_model_state(ModelState.from_model(Magazine))
-        rendered_state = project_state.render()
-        self.assertEqual(len(rendered_state.get_models()), 3)
+        self.assertEqual(len(project_state.apps.get_models()), 3)
 
         # now make an invalid one with a ForeignKey
         project_state = ProjectState()
         project_state.add_model_state(ModelState.from_model(Book))
         with self.assertRaises(ValueError):
-            rendered_state = project_state.render()
+            project_state.apps
 
         # and another with ManyToManyField
         project_state = ProjectState()
         project_state.add_model_state(ModelState.from_model(Magazine))
         with self.assertRaises(ValueError):
-            rendered_state = project_state.render()
+            project_state.apps
 
     def test_real_apps(self):
         """
@@ -465,12 +463,12 @@ class StateTests(TestCase):
         project_state = ProjectState()
         project_state.add_model_state(ModelState.from_model(TestModel))
         with self.assertRaises(ValueError):
-            project_state.render()
+            project_state.apps
 
         # If we include the real app it should succeed
         project_state = ProjectState(real_apps=["contenttypes"])
         project_state.add_model_state(ModelState.from_model(TestModel))
-        rendered_state = project_state.render()
+        rendered_state = project_state.apps
         self.assertEqual(
             len([x for x in rendered_state.get_models() if x._meta.app_label == "migrations"]),
             1,
@@ -538,4 +536,4 @@ class ModelStateTests(TestCase):
         project_state = ProjectState()
         project_state.add_model_state(state)
         with self.assertRaisesMessage(InvalidBasesError, "Cannot resolve bases for [<ModelState: 'app.Model'>]"):
-            project_state.render()
+            project_state.apps