Populated non-master app registries.

This removes the gap between the master app registry and ad-hoc app
registries created by the migration framework, specifically in terms
of behavior of the get_model[s] methods.

This commit contains a stealth feature that I'd rather not describe.

django/apps/base.py

@@ -53,7 +53,7 @@ class AppConfig(object):
         self.models = None
 
     def __repr__(self):
-        return '<AppConfig: %s>' % self.label
+        return '<%s: %s>' % (self.__class__.__name__, self.label)
 
     @classmethod
     def create(cls, entry):

django/apps/registry.py

@@ -27,9 +27,8 @@ class Apps(object):
         if master and hasattr(sys.modules[__name__], 'apps'):
             raise RuntimeError("You may create only one master registry.")
 
-        # When master is set to False, the registry isn't populated from
-        # INSTALLED_APPS and ignores the only_installed arguments to
-        # get_model[s].
+        # When master is set to False, the registry ignores the only_installed
+        # arguments to get_model[s].
         self.master = master
 
         # Mapping of app labels => model names => model classes. Every time a
@@ -48,9 +47,9 @@ class Apps(object):
         # set_available_apps and set_installed_apps.
         self.stored_app_configs = []
 
-        # Internal flags used when populating the master registry.
-        self._apps_loaded = not self.master
-        self._models_loaded = not self.master
+        # Internal flags used when populating the registry.
+        self._apps_loaded = False
+        self._models_loaded = False
 
         # Pending lookups for lazy relations.
         self._pending_lookups = {}
@@ -82,8 +81,11 @@ class Apps(object):
             # Therefore we simply import them sequentially.
             if installed_apps is None:
                 installed_apps = settings.INSTALLED_APPS
-            for app_name in installed_apps:
-                app_config = AppConfig.create(app_name)
+            for entry in installed_apps:
+                if isinstance(entry, AppConfig):
+                    app_config = entry
+                else:
+                    app_config = AppConfig.create(entry)
                 self.app_configs[app_config.label] = app_config
 
             self.get_models.cache_clear()

django/db/migrations/state.py

@@ -1,3 +1,4 @@
+from django.apps import AppConfig
 from django.apps.registry import Apps
 from django.db import models
 from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
@@ -33,6 +34,11 @@ class ProjectState(object):
         "Turns the project state into actual models in a new Apps"
         if self.apps is None:
             self.apps = Apps()
+            # Populate the app registry with a stub for each application.
+            app_labels = set(model_state.app_label for model_state in self.models.values())
+            app_configs = [AppConfigStub(label) for label in sorted(app_labels)]
+            self.apps.populate_apps(app_configs)
+            self.apps.populate_models()
             # 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/
@@ -68,6 +74,19 @@ class ProjectState(object):
         return not (self == other)
 
 
+class AppConfigStub(AppConfig):
+    """
+    Stubs a Django AppConfig. Only provides a label and a dict of models.
+    """
+    def __init__(self, label):
+        self.label = label
+        self.path = None
+        super(AppConfigStub, self).__init__(None, None)
+
+    def import_models(self, all_models):
+        self.models = all_models
+
+
 class ModelState(object):
     """
     Represents a Django Model. We don't use the actual Model class

tests/apps/tests.py

@@ -50,8 +50,10 @@ class AppsTests(TestCase):
         Tests the ready property of a registry other than the master.
         """
         apps = Apps()
-        # Currently, non-master app registries are artificially considered
-        # ready regardless of whether populate_models() has run.
+        self.assertFalse(apps.ready)
+        apps.populate_apps([])
+        self.assertFalse(apps.ready)
+        apps.populate_models()
         self.assertTrue(apps.ready)
 
     def test_bad_app_config(self):