Moved django.db.models.loading to django.apps.cache.

This commit doesn't contain any code changes; it's purely a refactoring.

40 files changed, 448 insertions, 419 deletions

diff --git a/django/apps/__init__.py b/django/apps/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/django/apps/__init__.py
diff --git a/django/apps/cache.py b/django/apps/cache.py
new file mode 100644
index 0000000000..a5b645646f
--- /dev/null
+++ b/django/apps/cache.py
@@ -0,0 +1,396 @@
+"Utilities for loading models and the modules that contain them."
+
+from collections import OrderedDict
+import copy
+import imp
+from importlib import import_module
+import os
+import sys
+
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.utils.module_loading import module_has_submodule
+from django.utils._os import upath
+from django.utils import six
+
+__all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models',
+        'load_app', 'app_cache_ready')
+
+MODELS_MODULE_NAME = 'models'
+
+
+class ModelDict(OrderedDict):
+    """
+    We need to special-case the deepcopy for this, as the keys are modules,
+    which can't be deep copied.
+    """
+    def __deepcopy__(self, memo):
+        return self.__class__([(key, copy.deepcopy(value, memo))
+                               for key, value in self.items()])
+
+
+class UnavailableApp(Exception):
+    pass
+
+
+def _initialize():
+    """
+    Returns a dictionary to be used as the initial value of the
+    [shared] state of the app cache.
+    """
+    return dict(
+        # Keys of app_store are the model modules for each application.
+        app_store=ModelDict(),
+
+        # Mapping of installed app_labels to model modules for that app.
+        app_labels={},
+
+        # Mapping of app_labels to a dictionary of model names to model code.
+        # May contain apps that are not installed.
+        app_models=ModelDict(),
+
+        # Mapping of app_labels to errors raised when trying to import the app.
+        app_errors={},
+
+        # Pending lookups for lazy relations
+        pending_lookups={},
+
+        # List of app_labels that allows restricting the set of apps.
+        # Used by TransactionTestCase.available_apps for performance reasons.
+        available_apps=None,
+
+        # -- Everything below here is only used when populating the cache --
+        loads_installed=True,
+        loaded=False,
+        handled=set(),
+        postponed=[],
+        nesting_level=0,
+        _get_models_cache={},
+    )
+
+
+class BaseAppCache(object):
+    """
+    A cache that stores installed applications and their models. Used to
+    provide reverse-relations and for app introspection (e.g. admin).
+
+    This provides the base (non-Borg) AppCache class - the AppCache
+    subclass adds borg-like behaviour for the few cases where it's needed.
+    """
+
+    def __init__(self):
+        self.__dict__ = _initialize()
+        # This stops _populate loading from INSTALLED_APPS and ignores the
+        # only_installed arguments to get_model[s]
+        self.loads_installed = False
+
+    def _populate(self):
+        """
+        Fill in all the cache information. This method is threadsafe, in the
+        sense that every caller will see the same state upon return, and if the
+        cache is already initialised, it does no work.
+        """
+        if self.loaded:
+            return
+        if not self.loads_installed:
+            self.loaded = True
+            return
+        # Note that we want to use the import lock here - the app loading is
+        # in many cases initiated implicitly by importing, and thus it is
+        # possible to end up in deadlock when one thread initiates loading
+        # without holding the importer lock and another thread then tries to
+        # import something which also launches the app loading. For details of
+        # this situation see #18251.
+        imp.acquire_lock()
+        try:
+            if self.loaded:
+                return
+            for app_name in settings.INSTALLED_APPS:
+                if app_name in self.handled:
+                    continue
+                self.load_app(app_name, True)
+            if not self.nesting_level:
+                for app_name in self.postponed:
+                    self.load_app(app_name)
+                self.loaded = True
+        finally:
+            imp.release_lock()
+
+    def _label_for(self, app_mod):
+        """
+        Return app_label for given models module.
+
+        """
+        return app_mod.__name__.split('.')[-2]
+
+    def load_app(self, app_name, can_postpone=False):
+        """
+        Loads the app with the provided fully qualified name, and returns the
+        model module.
+        """
+        app_module = import_module(app_name)
+        self.handled.add(app_name)
+        self.nesting_level += 1
+        try:
+            models = import_module('%s.%s' % (app_name, MODELS_MODULE_NAME))
+        except ImportError:
+            self.nesting_level -= 1
+            # If the app doesn't have a models module, we can just ignore the
+            # ImportError and return no models for it.
+            if not module_has_submodule(app_module, MODELS_MODULE_NAME):
+                return None
+            # But if the app does have a models module, we need to figure out
+            # whether to suppress or propagate the error. If can_postpone is
+            # True then it may be that the package is still being imported by
+            # Python and the models module isn't available yet. So we add the
+            # app to the postponed list and we'll try it again after all the
+            # recursion has finished (in populate). If can_postpone is False
+            # then it's time to raise the ImportError.
+            else:
+                if can_postpone:
+                    self.postponed.append(app_name)
+                    return None
+                else:
+                    raise
+
+        self.nesting_level -= 1
+        if models not in self.app_store:
+            self.app_store[models] = len(self.app_store)
+            self.app_labels[self._label_for(models)] = models
+        return models
+
+    def app_cache_ready(self):
+        """
+        Returns true if the model cache is fully populated.
+
+        Useful for code that wants to cache the results of get_models() for
+        themselves once it is safe to do so.
+        """
+        return self.loaded
+
+    def get_apps(self):
+        """
+        Returns a list of all installed modules that contain models.
+        """
+        self._populate()
+
+        apps = self.app_store.items()
+        if self.available_apps is not None:
+            apps = [elt for elt in apps
+                    if self._label_for(elt[0]) in self.available_apps]
+
+        # Ensure the returned list is always in the same order (with new apps
+        # added at the end). This avoids unstable ordering on the admin app
+        # list page, for example.
+        apps = sorted(apps, key=lambda elt: elt[1])
+
+        return [elt[0] for elt in apps]
+
+    def _get_app_package(self, app):
+        return '.'.join(app.__name__.split('.')[:-1])
+
+    def get_app_package(self, app_label):
+        return self._get_app_package(self.get_app(app_label))
+
+    def _get_app_path(self, app):
+        if hasattr(app, '__path__'):        # models/__init__.py package
+            app_path = app.__path__[0]
+        else:                               # models.py module
+            app_path = app.__file__
+        return os.path.dirname(upath(app_path))
+
+    def get_app_path(self, app_label):
+        return self._get_app_path(self.get_app(app_label))
+
+    def get_app_paths(self):
+        """
+        Returns a list of paths to all installed apps.
+
+        Useful for discovering files at conventional locations inside apps
+        (static files, templates, etc.)
+        """
+        self._populate()
+
+        app_paths = []
+        for app in self.get_apps():
+            app_paths.append(self._get_app_path(app))
+        return app_paths
+
+    def get_app(self, app_label, emptyOK=False):
+        """
+        Returns the module containing the models for the given app_label.
+
+        Returns None if the app has no models in it and emptyOK is True.
+
+        Raises UnavailableApp when set_available_apps() in in effect and
+        doesn't include app_label.
+        """
+        self._populate()
+        imp.acquire_lock()
+        try:
+            for app_name in settings.INSTALLED_APPS:
+                if app_label == app_name.split('.')[-1]:
+                    mod = self.load_app(app_name, False)
+                    if mod is None and not emptyOK:
+                        raise ImproperlyConfigured("App with label %s is missing a models.py module." % app_label)
+                    if self.available_apps is not None and app_label not in self.available_apps:
+                        raise UnavailableApp("App with label %s isn't available." % app_label)
+                    return mod
+            raise ImproperlyConfigured("App with label %s could not be found" % app_label)
+        finally:
+            imp.release_lock()
+
+    def get_app_errors(self):
+        "Returns the map of known problems with the INSTALLED_APPS."
+        self._populate()
+        return self.app_errors
+
+    def get_models(self, app_mod=None,
+                   include_auto_created=False, include_deferred=False,
+                   only_installed=True, include_swapped=False):
+        """
+        Given a module containing models, returns a list of the models.
+        Otherwise returns a list of all installed models.
+
+        By default, auto-created models (i.e., m2m models without an
+        explicit intermediate table) are not included. However, if you
+        specify include_auto_created=True, they will be.
+
+        By default, models created to satisfy deferred attribute
+        queries are *not* included in the list of models. However, if
+        you specify include_deferred, they will be.
+
+        By default, models that aren't part of installed apps will *not*
+        be included in the list of models. However, if you specify
+        only_installed=False, they will be. If you're using a non-default
+        AppCache, this argument does nothing - all models will be included.
+
+        By default, models that have been swapped out will *not* be
+        included in the list of models. However, if you specify
+        include_swapped, they will be.
+        """
+        if not self.loads_installed:
+            only_installed = False
+        cache_key = (app_mod, include_auto_created, include_deferred, only_installed, include_swapped)
+        model_list = None
+        try:
+            model_list = self._get_models_cache[cache_key]
+            if self.available_apps is not None and only_installed:
+                model_list = [m for m in model_list if m._meta.app_label in self.available_apps]
+            return model_list
+        except KeyError:
+            pass
+        self._populate()
+        if app_mod:
+            if app_mod in self.app_store:
+                app_list = [self.app_models.get(self._label_for(app_mod), ModelDict())]
+            else:
+                app_list = []
+        else:
+            if only_installed:
+                app_list = [self.app_models.get(app_label, ModelDict())
+                            for app_label in six.iterkeys(self.app_labels)]
+            else:
+                app_list = six.itervalues(self.app_models)
+        model_list = []
+        for app in app_list:
+            model_list.extend(
+                model for model in app.values()
+                if ((not model._deferred or include_deferred) and
+                    (not model._meta.auto_created or include_auto_created) and
+                    (not model._meta.swapped or include_swapped))
+            )
+        self._get_models_cache[cache_key] = model_list
+        if self.available_apps is not None and only_installed:
+            model_list = [m for m in model_list if m._meta.app_label in self.available_apps]
+        return model_list
+
+    def get_model(self, app_label, model_name,
+                  seed_cache=True, only_installed=True):
+        """
+        Returns the model matching the given app_label and case-insensitive
+        model_name.
+
+        Returns None if no model is found.
+
+        Raises UnavailableApp when set_available_apps() in in effect and
+        doesn't include app_label.
+        """
+        if not self.loads_installed:
+            only_installed = False
+        if seed_cache:
+            self._populate()
+        if only_installed and app_label not in self.app_labels:
+            return None
+        if (self.available_apps is not None and only_installed
+                and app_label not in self.available_apps):
+            raise UnavailableApp("App with label %s isn't available." % app_label)
+        try:
+            return self.app_models[app_label][model_name.lower()]
+        except KeyError:
+            return None
+
+    def register_models(self, app_label, *models):
+        """
+        Register a set of models as belonging to an app.
+        """
+        for model in models:
+            # Store as 'name: model' pair in a dictionary
+            # in the app_models dictionary
+            model_name = model._meta.model_name
+            model_dict = self.app_models.setdefault(app_label, ModelDict())
+            if model_name in model_dict:
+                # The same model may be imported via different paths (e.g.
+                # appname.models and project.appname.models). We use the source
+                # filename as a means to detect identity.
+                fname1 = os.path.abspath(upath(sys.modules[model.__module__].__file__))
+                fname2 = os.path.abspath(upath(sys.modules[model_dict[model_name].__module__].__file__))
+                # Since the filename extension could be .py the first time and
+                # .pyc or .pyo the second time, ignore the extension when
+                # comparing.
+                if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]:
+                    continue
+            model_dict[model_name] = model
+        self._get_models_cache.clear()
+
+    def set_available_apps(self, available):
+        if not set(available).issubset(set(settings.INSTALLED_APPS)):
+            extra = set(available) - set(settings.INSTALLED_APPS)
+            raise ValueError("Available apps isn't a subset of installed "
+                "apps, extra apps: " + ", ".join(extra))
+        self.available_apps = set(app.rsplit('.', 1)[-1] for app in available)
+
+    def unset_available_apps(self):
+        self.available_apps = None
+
+
+class AppCache(BaseAppCache):
+    """
+    A cache that stores installed applications and their models. Used to
+    provide reverse-relations and for app introspection (e.g. admin).
+
+    Borg version of the BaseAppCache class.
+    """
+
+    __shared_state = _initialize()
+
+    def __init__(self):
+        self.__dict__ = self.__shared_state
+
+
+cache = AppCache()
+
+
+# These methods were always module level, so are kept that way for backwards
+# compatibility.
+get_apps = cache.get_apps
+get_app_package = cache.get_app_package
+get_app_path = cache.get_app_path
+get_app_paths = cache.get_app_paths
+get_app = cache.get_app
+get_app_errors = cache.get_app_errors
+get_models = cache.get_models
+get_model = cache.get_model
+register_models = cache.register_models
+load_app = cache.load_app
+app_cache_ready = cache.app_cache_ready
diff --git a/django/contrib/auth/tests/test_management.py b/django/contrib/auth/tests/test_management.py
index bd51f39977..698947d57c 100644
--- a/django/contrib/auth/tests/test_management.py
+++ b/django/contrib/auth/tests/test_management.py
@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 from datetime import date
 
+from django.apps.cache import get_app
 from django.contrib.auth import models, management
 from django.contrib.auth.management import create_permissions
 from django.contrib.auth.management.commands import changepassword
@@ -12,7 +13,6 @@ from django.core import exceptions
 from django.core.management import call_command
 from django.core.management.base import CommandError
 from django.core.management.validation import get_validation_errors
-from django.db.models.loading import get_app
 from django.test import TestCase
 from django.test.utils import override_settings
 from django.utils import six
diff --git a/django/core/management/commands/makemigrations.py b/django/core/management/commands/makemigrations.py
index 239a0a416c..7c4bb4f7cf 100644
--- a/django/core/management/commands/makemigrations.py
+++ b/django/core/management/commands/makemigrations.py
@@ -3,6 +3,7 @@ import os
 import operator
 from optparse import make_option
 
+from django.apps.cache import cache
 from django.core.management.base import BaseCommand, CommandError
 from django.core.exceptions import ImproperlyConfigured
 from django.db import connections, DEFAULT_DB_ALIAS, migrations
@@ -11,7 +12,6 @@ from django.db.migrations.autodetector import MigrationAutodetector
 from django.db.migrations.questioner import MigrationQuestioner, InteractiveMigrationQuestioner
 from django.db.migrations.state import ProjectState
 from django.db.migrations.writer import MigrationWriter
-from django.db.models.loading import cache
 from django.utils.six.moves import reduce
 
 
diff --git a/django/core/management/commands/migrate.py b/django/core/management/commands/migrate.py
index 093c8a79d0..1966223042 100644
--- a/django/core/management/commands/migrate.py
+++ b/django/core/management/commands/migrate.py
@@ -6,6 +6,7 @@ from importlib import import_module
 import itertools
 import traceback
 
+from django.apps.cache import cache
 from django.conf import settings
 from django.core.management import call_command
 from django.core.management.base import BaseCommand, CommandError
@@ -16,7 +17,6 @@ from django.db.migrations.executor import MigrationExecutor
 from django.db.migrations.loader import MigrationLoader, AmbiguityError
 from django.db.migrations.state import ProjectState
 from django.db.migrations.autodetector import MigrationAutodetector
-from django.db.models.loading import cache
 from django.utils.module_loading import module_has_submodule
 
 
diff --git a/django/core/management/commands/shell.py b/django/core/management/commands/shell.py
index 00a6602c0b..0d84c9b2ec 100644
--- a/django/core/management/commands/shell.py
+++ b/django/core/management/commands/shell.py
@@ -66,7 +66,7 @@ class Command(NoArgsCommand):
     def handle_noargs(self, **options):
         # XXX: (Temporary) workaround for ticket #1796: force early loading of all
         # models from installed apps.
-        from django.db.models.loading import get_models
+        from django.apps.cache import get_models
         get_models()
 
         use_plain = options.get('plain', False)
diff --git a/django/core/management/validation.py b/django/core/management/validation.py
index 6bdcf853d4..459923a088 100644
--- a/django/core/management/validation.py
+++ b/django/core/management/validation.py
@@ -26,8 +26,8 @@ def get_validation_errors(outfile, app=None):
     validates all models of all installed apps. Writes errors, if any, to outfile.
     Returns number of errors.
     """
+    from django.apps.cache import get_app_errors
     from django.db import connection, models
-    from django.db.models.loading import get_app_errors
     from django.db.models.deletion import SET_NULL, SET_DEFAULT
 
     e = ModelErrorCollection(outfile)
diff --git a/django/db/backends/sqlite3/schema.py b/django/db/backends/sqlite3/schema.py
index f04095507f..69e3b61b87 100644
--- a/django/db/backends/sqlite3/schema.py
+++ b/django/db/backends/sqlite3/schema.py
@@ -1,6 +1,6 @@
+from django.apps.cache import BaseAppCache
 from django.db.backends.schema import BaseDatabaseSchemaEditor
 from django.db.models.fields.related import ManyToManyField
-from django.db.models.loading import BaseAppCache
 
 
 class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
diff --git a/django/db/migrations/loader.py b/django/db/migrations/loader.py
index f2510b8368..101588c4a1 100644
--- a/django/db/migrations/loader.py
+++ b/django/db/migrations/loader.py
@@ -1,7 +1,7 @@
 import os
 import sys
 from importlib import import_module
-from django.db.models.loading import cache
+from django.apps.cache import cache
 from django.db.migrations.recorder import MigrationRecorder
 from django.db.migrations.graph import MigrationGraph
 from django.utils import six
diff --git a/django/db/migrations/questioner.py b/django/db/migrations/questioner.py
index 7e798d3105..7874f23ed0 100644
--- a/django/db/migrations/questioner.py
+++ b/django/db/migrations/questioner.py
@@ -2,7 +2,7 @@ import importlib
 import os
 import sys
 
-from django.db.models.loading import cache
+from django.apps.cache import cache
 from django.utils import datetime_safe
 from django.utils.six.moves import input
 from django.core.exceptions import ImproperlyConfigured
diff --git a/django/db/migrations/recorder.py b/django/db/migrations/recorder.py
index be804e52aa..bf1cd225c2 100644
--- a/django/db/migrations/recorder.py
+++ b/django/db/migrations/recorder.py
@@ -1,5 +1,5 @@
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.utils.timezone import now
 
 
diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 769b0005f8..6aa44ba108 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -1,5 +1,5 @@
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
 from django.utils import six
 from django.utils.module_loading import import_by_path
diff --git a/django/db/migrations/writer.py b/django/db/migrations/writer.py
index 22b0977ba4..150455b09c 100644
--- a/django/db/migrations/writer.py
+++ b/django/db/migrations/writer.py
@@ -3,12 +3,12 @@ import datetime
 import types
 import os
 from importlib import import_module
-from django.utils import six
+from django.apps.cache import cache
 from django.db import models
-from django.db.models.loading import cache
 from django.db.migrations.loader import MigrationLoader
 from django.utils.encoding import force_text
 from django.utils.functional import Promise
+from django.utils import six
 
 
 class MigrationWriter(object):
diff --git a/django/db/models/__init__.py b/django/db/models/__init__.py
index 12c31f89fd..ad76347494 100644
--- a/django/db/models/__init__.py
+++ b/django/db/models/__init__.py
@@ -1,9 +1,9 @@
 from functools import wraps
 
-from django.core.exceptions import ObjectDoesNotExist, ImproperlyConfigured  # NOQA
-from django.db.models.loading import (  # NOQA
+from django.apps.cache import (  # NOQA
     get_apps, get_app_path, get_app_paths, get_app, get_models, get_model,
     register_models, UnavailableApp)
+from django.core.exceptions import ObjectDoesNotExist, ImproperlyConfigured  # NOQA
 from django.db.models.query import Q, QuerySet, Prefetch  # NOQA
 from django.db.models.expressions import F  # NOQA
 from django.db.models.manager import Manager  # NOQA
diff --git a/django/db/models/base.py b/django/db/models/base.py
index dd4850c3d4..f22506aa92 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -5,6 +5,7 @@ import sys
 from functools import update_wrapper
 from django.utils.six.moves import zip
 
+from django.apps.cache import get_model, MODELS_MODULE_NAME
 import django.db.models.manager  # NOQA: Imported to register signal handler.
 from django.conf import settings
 from django.core.exceptions import (ObjectDoesNotExist,
@@ -19,7 +20,6 @@ from django.db.models.query_utils import DeferredAttribute, deferred_class_facto
 from django.db.models.deletion import Collector
 from django.db.models.options import Options
 from django.db.models import signals
-from django.db.models.loading import get_model, MODELS_MODULE_NAME
 from django.utils.translation import ugettext_lazy as _
 from django.utils.functional import curry
 from django.utils.encoding import force_str, force_text
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 33adaedc7e..d69a4346e2 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -9,8 +9,8 @@ import warnings
 from base64 import b64decode, b64encode
 from itertools import tee
 
+from django.apps.cache import get_model
 from django.db import connection
-from django.db.models.loading import get_model
 from django.db.models.query_utils import QueryWrapper
 from django.conf import settings
 from django import forms
diff --git a/django/db/models/loading.py b/django/db/models/loading.py
index 21440216e0..795de130b5 100644
--- a/django/db/models/loading.py
+++ b/django/db/models/loading.py
@@ -1,387 +1,15 @@
-"Utilities for loading models and the modules that contain them."
+import warnings
 
-from collections import OrderedDict
-import copy
-import imp
-from importlib import import_module
-import os
-import sys
+from django.apps.cache import cache
 
-from django.conf import settings
-from django.core.exceptions import ImproperlyConfigured
-from django.utils.module_loading import module_has_submodule
-from django.utils._os import upath
-from django.utils import six
+warnings.warn(
+    "The utilities in django.db.models.loading are deprecated "
+    "in favor of the new application loading system.",
+    PendingDeprecationWarning, stacklevel=2)
 
 __all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models',
         'load_app', 'app_cache_ready')
 
-MODELS_MODULE_NAME = 'models'
-
-
-class ModelDict(OrderedDict):
-    """
-    We need to special-case the deepcopy for this, as the keys are modules,
-    which can't be deep copied.
-    """
-    def __deepcopy__(self, memo):
-        return self.__class__([(key, copy.deepcopy(value, memo))
-                               for key, value in self.items()])
-
-
-class UnavailableApp(Exception):
-    pass
-
-
-def _initialize():
-    """
-    Returns a dictionary to be used as the initial value of the
-    [shared] state of the app cache.
-    """
-    return dict(
-        # Keys of app_store are the model modules for each application.
-        app_store=ModelDict(),
-
-        # Mapping of installed app_labels to model modules for that app.
-        app_labels={},
-
-        # Mapping of app_labels to a dictionary of model names to model code.
-        # May contain apps that are not installed.
-        app_models=ModelDict(),
-
-        # Mapping of app_labels to errors raised when trying to import the app.
-        app_errors={},
-
-        # Pending lookups for lazy relations
-        pending_lookups={},
-
-        # List of app_labels that allows restricting the set of apps.
-        # Used by TransactionTestCase.available_apps for performance reasons.
-        available_apps=None,
-
-        # -- Everything below here is only used when populating the cache --
-        loads_installed=True,
-        loaded=False,
-        handled=set(),
-        postponed=[],
-        nesting_level=0,
-        _get_models_cache={},
-    )
-
-
-class BaseAppCache(object):
-    """
-    A cache that stores installed applications and their models. Used to
-    provide reverse-relations and for app introspection (e.g. admin).
-
-    This provides the base (non-Borg) AppCache class - the AppCache
-    subclass adds borg-like behaviour for the few cases where it's needed.
-    """
-
-    def __init__(self):
-        self.__dict__ = _initialize()
-        # This stops _populate loading from INSTALLED_APPS and ignores the
-        # only_installed arguments to get_model[s]
-        self.loads_installed = False
-
-    def _populate(self):
-        """
-        Fill in all the cache information. This method is threadsafe, in the
-        sense that every caller will see the same state upon return, and if the
-        cache is already initialised, it does no work.
-        """
-        if self.loaded:
-            return
-        if not self.loads_installed:
-            self.loaded = True
-            return
-        # Note that we want to use the import lock here - the app loading is
-        # in many cases initiated implicitly by importing, and thus it is
-        # possible to end up in deadlock when one thread initiates loading
-        # without holding the importer lock and another thread then tries to
-        # import something which also launches the app loading. For details of
-        # this situation see #18251.
-        imp.acquire_lock()
-        try:
-            if self.loaded:
-                return
-            for app_name in settings.INSTALLED_APPS:
-                if app_name in self.handled:
-                    continue
-                self.load_app(app_name, True)
-            if not self.nesting_level:
-                for app_name in self.postponed:
-                    self.load_app(app_name)
-                self.loaded = True
-        finally:
-            imp.release_lock()
-
-    def _label_for(self, app_mod):
-        """
-        Return app_label for given models module.
-
-        """
-        return app_mod.__name__.split('.')[-2]
-
-    def load_app(self, app_name, can_postpone=False):
-        """
-        Loads the app with the provided fully qualified name, and returns the
-        model module.
-        """
-        app_module = import_module(app_name)
-        self.handled.add(app_name)
-        self.nesting_level += 1
-        try:
-            models = import_module('%s.%s' % (app_name, MODELS_MODULE_NAME))
-        except ImportError:
-            self.nesting_level -= 1
-            # If the app doesn't have a models module, we can just ignore the
-            # ImportError and return no models for it.
-            if not module_has_submodule(app_module, MODELS_MODULE_NAME):
-                return None
-            # But if the app does have a models module, we need to figure out
-            # whether to suppress or propagate the error. If can_postpone is
-            # True then it may be that the package is still being imported by
-            # Python and the models module isn't available yet. So we add the
-            # app to the postponed list and we'll try it again after all the
-            # recursion has finished (in populate). If can_postpone is False
-            # then it's time to raise the ImportError.
-            else:
-                if can_postpone:
-                    self.postponed.append(app_name)
-                    return None
-                else:
-                    raise
-
-        self.nesting_level -= 1
-        if models not in self.app_store:
-            self.app_store[models] = len(self.app_store)
-            self.app_labels[self._label_for(models)] = models
-        return models
-
-    def app_cache_ready(self):
-        """
-        Returns true if the model cache is fully populated.
-
-        Useful for code that wants to cache the results of get_models() for
-        themselves once it is safe to do so.
-        """
-        return self.loaded
-
-    def get_apps(self):
-        """
-        Returns a list of all installed modules that contain models.
-        """
-        self._populate()
-
-        apps = self.app_store.items()
-        if self.available_apps is not None:
-            apps = [elt for elt in apps
-                    if self._label_for(elt[0]) in self.available_apps]
-
-        # Ensure the returned list is always in the same order (with new apps
-        # added at the end). This avoids unstable ordering on the admin app
-        # list page, for example.
-        apps = sorted(apps, key=lambda elt: elt[1])
-
-        return [elt[0] for elt in apps]
-
-    def _get_app_package(self, app):
-        return '.'.join(app.__name__.split('.')[:-1])
-
-    def get_app_package(self, app_label):
-        return self._get_app_package(self.get_app(app_label))
-
-    def _get_app_path(self, app):
-        if hasattr(app, '__path__'):        # models/__init__.py package
-            app_path = app.__path__[0]
-        else:                               # models.py module
-            app_path = app.__file__
-        return os.path.dirname(upath(app_path))
-
-    def get_app_path(self, app_label):
-        return self._get_app_path(self.get_app(app_label))
-
-    def get_app_paths(self):
-        """
-        Returns a list of paths to all installed apps.
-
-        Useful for discovering files at conventional locations inside apps
-        (static files, templates, etc.)
-        """
-        self._populate()
-
-        app_paths = []
-        for app in self.get_apps():
-            app_paths.append(self._get_app_path(app))
-        return app_paths
-
-    def get_app(self, app_label, emptyOK=False):
-        """
-        Returns the module containing the models for the given app_label.
-
-        Returns None if the app has no models in it and emptyOK is True.
-
-        Raises UnavailableApp when set_available_apps() in in effect and
-        doesn't include app_label.
-        """
-        self._populate()
-        imp.acquire_lock()
-        try:
-            for app_name in settings.INSTALLED_APPS:
-                if app_label == app_name.split('.')[-1]:
-                    mod = self.load_app(app_name, False)
-                    if mod is None and not emptyOK:
-                        raise ImproperlyConfigured("App with label %s is missing a models.py module." % app_label)
-                    if self.available_apps is not None and app_label not in self.available_apps:
-                        raise UnavailableApp("App with label %s isn't available." % app_label)
-                    return mod
-            raise ImproperlyConfigured("App with label %s could not be found" % app_label)
-        finally:
-            imp.release_lock()
-
-    def get_app_errors(self):
-        "Returns the map of known problems with the INSTALLED_APPS."
-        self._populate()
-        return self.app_errors
-
-    def get_models(self, app_mod=None,
-                   include_auto_created=False, include_deferred=False,
-                   only_installed=True, include_swapped=False):
-        """
-        Given a module containing models, returns a list of the models.
-        Otherwise returns a list of all installed models.
-
-        By default, auto-created models (i.e., m2m models without an
-        explicit intermediate table) are not included. However, if you
-        specify include_auto_created=True, they will be.
-
-        By default, models created to satisfy deferred attribute
-        queries are *not* included in the list of models. However, if
-        you specify include_deferred, they will be.
-
-        By default, models that aren't part of installed apps will *not*
-        be included in the list of models. However, if you specify
-        only_installed=False, they will be. If you're using a non-default
-        AppCache, this argument does nothing - all models will be included.
-
-        By default, models that have been swapped out will *not* be
-        included in the list of models. However, if you specify
-        include_swapped, they will be.
-        """
-        if not self.loads_installed:
-            only_installed = False
-        cache_key = (app_mod, include_auto_created, include_deferred, only_installed, include_swapped)
-        model_list = None
-        try:
-            model_list = self._get_models_cache[cache_key]
-            if self.available_apps is not None and only_installed:
-                model_list = [m for m in model_list if m._meta.app_label in self.available_apps]
-
-            return model_list
-        except KeyError:
-            pass
-        self._populate()
-        if app_mod:
-            if app_mod in self.app_store:
-                app_list = [self.app_models.get(self._label_for(app_mod), ModelDict())]
-            else:
-                app_list = []
-        else:
-            if only_installed:
-                app_list = [self.app_models.get(app_label, ModelDict())
-                            for app_label in six.iterkeys(self.app_labels)]
-            else:
-                app_list = six.itervalues(self.app_models)
-        model_list = []
-        for app in app_list:
-            model_list.extend(
-                model for model in app.values()
-                if ((not model._deferred or include_deferred) and
-                    (not model._meta.auto_created or include_auto_created) and
-                    (not model._meta.swapped or include_swapped))
-            )
-        self._get_models_cache[cache_key] = model_list
-        if self.available_apps is not None and only_installed:
-            model_list = [m for m in model_list if m._meta.app_label in self.available_apps]
-        return model_list
-
-    def get_model(self, app_label, model_name,
-                  seed_cache=True, only_installed=True):
-        """
-        Returns the model matching the given app_label and case-insensitive
-        model_name.
-
-        Returns None if no model is found.
-
-        Raises UnavailableApp when set_available_apps() in in effect and
-        doesn't include app_label.
-        """
-        if not self.loads_installed:
-            only_installed = False
-        if seed_cache:
-            self._populate()
-        if only_installed and app_label not in self.app_labels:
-            return None
-        if (self.available_apps is not None and only_installed
-                and app_label not in self.available_apps):
-            raise UnavailableApp("App with label %s isn't available." % app_label)
-        try:
-            return self.app_models[app_label][model_name.lower()]
-        except KeyError:
-            return None
-
-    def register_models(self, app_label, *models):
-        """
-        Register a set of models as belonging to an app.
-        """
-        for model in models:
-            # Store as 'name: model' pair in a dictionary
-            # in the app_models dictionary
-            model_name = model._meta.model_name
-            model_dict = self.app_models.setdefault(app_label, ModelDict())
-            if model_name in model_dict:
-                # The same model may be imported via different paths (e.g.
-                # appname.models and project.appname.models). We use the source
-                # filename as a means to detect identity.
-                fname1 = os.path.abspath(upath(sys.modules[model.__module__].__file__))
-                fname2 = os.path.abspath(upath(sys.modules[model_dict[model_name].__module__].__file__))
-                # Since the filename extension could be .py the first time and
-                # .pyc or .pyo the second time, ignore the extension when
-                # comparing.
-                if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]:
-                    continue
-            model_dict[model_name] = model
-        self._get_models_cache.clear()
-
-    def set_available_apps(self, available):
-        if not set(available).issubset(set(settings.INSTALLED_APPS)):
-            extra = set(available) - set(settings.INSTALLED_APPS)
-            raise ValueError("Available apps isn't a subset of installed "
-                "apps, extra apps: " + ", ".join(extra))
-        self.available_apps = set(app.rsplit('.', 1)[-1] for app in available)
-
-    def unset_available_apps(self):
-        self.available_apps = None
-
-
-class AppCache(BaseAppCache):
-    """
-    A cache that stores installed applications and their models. Used to
-    provide reverse-relations and for app introspection (e.g. admin).
-
-    Borg version of the BaseAppCache class.
-    """
-
-    __shared_state = _initialize()
-
-    def __init__(self):
-        self.__dict__ = self.__shared_state
-
-
-cache = AppCache()
-
-
 # These methods were always module level, so are kept that way for backwards
 # compatibility.
 get_apps = cache.get_apps
diff --git a/django/db/models/options.py b/django/db/models/options.py
index b14e61573c..5d99066343 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -5,11 +5,11 @@ import re
 from bisect import bisect
 import warnings
 
+from django.apps.cache import app_cache_ready, cache
 from django.conf import settings
 from django.db.models.fields.related import ManyToManyRel
 from django.db.models.fields import AutoField, FieldDoesNotExist
 from django.db.models.fields.proxy import OrderWrt
-from django.db.models.loading import app_cache_ready, cache
 from django.utils import six
 from django.utils.functional import cached_property
 from django.utils.encoding import force_text, smart_text, python_2_unicode_compatible
diff --git a/django/db/models/signals.py b/django/db/models/signals.py
index 6b011c2099..2543cf5f4a 100644
--- a/django/db/models/signals.py
+++ b/django/db/models/signals.py
@@ -1,6 +1,6 @@
 from collections import defaultdict
 
-from django.db.models.loading import get_model
+from django.apps.cache import get_model
 from django.dispatch import Signal
 from django.utils import six
 
diff --git a/django/test/testcases.py b/django/test/testcases.py
index 4dbff55204..52900ec478 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -15,6 +15,7 @@ import unittest
 from unittest import skipIf         # NOQA: Imported here for backward compatibility
 from unittest.util import safe_repr
 
+from django.apps.cache import cache
 from django.conf import settings
 from django.core import mail
 from django.core.exceptions import ValidationError, ImproperlyConfigured
@@ -25,7 +26,6 @@ from django.core.management.commands import flush
 from django.core.servers.basehttp import WSGIRequestHandler, WSGIServer
 from django.core.urlresolvers import clear_url_caches, set_urlconf
 from django.db import connection, connections, DEFAULT_DB_ALIAS, transaction
-from django.db.models.loading import cache
 from django.forms.fields import CharField
 from django.http import QueryDict
 from django.test.client import Client
diff --git a/docs/internals/deprecation.txt b/docs/internals/deprecation.txt
index 2e53901536..d548f275fe 100644
--- a/docs/internals/deprecation.txt
+++ b/docs/internals/deprecation.txt
@@ -222,6 +222,9 @@ these changes.
 * ``django.core.cache.get_cache`` will be removed. Add suitable entries
   to :setting:`CACHES` and use :data:`django.core.cache.caches` instead.
 
+* ``django.db.models.loading`` will be removed. Use the new application
+  loading APIs instead.
+
 2.0
 ---
 
diff --git a/tests/app_cache/models.py b/tests/app_cache/models.py
index 1b4d33c2f9..cc092390ab 100644
--- a/tests/app_cache/models.py
+++ b/tests/app_cache/models.py
@@ -1,5 +1,5 @@
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 
 # We're testing app cache presence on load, so this is handy.
 
diff --git a/tests/app_cache/tests.py b/tests/app_cache/tests.py
index b72b862de3..564f9f6f48 100644
--- a/tests/app_cache/tests.py
+++ b/tests/app_cache/tests.py
@@ -1,7 +1,9 @@
 from __future__ import absolute_import
-from django.test import TestCase
-from django.db.models.loading import cache, BaseAppCache
+
+from django.apps.cache import cache, BaseAppCache
 from django.db import models
+from django.test import TestCase
+
 from .models import TotallyNormal, SoAlternative, new_app_cache
 
 
diff --git a/tests/app_loading/tests.py b/tests/app_loading/tests.py
index 20ec064d69..4795ca4139 100644
--- a/tests/app_loading/tests.py
+++ b/tests/app_loading/tests.py
@@ -5,7 +5,7 @@ import os
 import sys
 from unittest import TestCase
 
-from django.db.models.loading import cache, load_app, get_model, get_models, AppCache
+from django.apps.cache import cache, load_app, get_model, get_models, AppCache
 from django.test.utils import override_settings
 from django.utils._os import upath
 
diff --git a/tests/contenttypes_tests/tests.py b/tests/contenttypes_tests/tests.py
index 9d1e1f77ea..a56d196933 100644
--- a/tests/contenttypes_tests/tests.py
+++ b/tests/contenttypes_tests/tests.py
@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
 
+from django.apps.cache import BaseAppCache
 from django.contrib.contenttypes.models import ContentType
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.test import TestCase
 
 from .models import Author, Article
diff --git a/tests/defer_regress/tests.py b/tests/defer_regress/tests.py
index c03388b50e..0107e8167c 100644
--- a/tests/defer_regress/tests.py
+++ b/tests/defer_regress/tests.py
@@ -2,10 +2,10 @@ from __future__ import unicode_literals
 
 from operator import attrgetter
 
+from django.apps.cache import cache
 from django.contrib.contenttypes.models import ContentType
 from django.contrib.sessions.backends.db import SessionStore
 from django.db.models import Count
-from django.db.models.loading import cache
 from django.test import TestCase
 from django.test.utils import override_settings
 
diff --git a/tests/empty/tests.py b/tests/empty/tests.py
index 007d04c363..2a9f568aea 100644
--- a/tests/empty/tests.py
+++ b/tests/empty/tests.py
@@ -1,5 +1,5 @@
+from django.apps.cache import get_app
 from django.core.exceptions import ImproperlyConfigured
-from django.db.models.loading import get_app
 from django.test import TestCase
 from django.test.utils import override_settings
 from django.utils import six
diff --git a/tests/invalid_models/tests.py b/tests/invalid_models/tests.py
index 9c9db91da9..2f7815f96d 100644
--- a/tests/invalid_models/tests.py
+++ b/tests/invalid_models/tests.py
@@ -2,8 +2,8 @@ import copy
 import sys
 import unittest
 
+from django.apps.cache import cache, load_app
 from django.core.management.validation import get_validation_errors
-from django.db.models.loading import cache, load_app
 from django.test.utils import override_settings
 from django.utils.six import StringIO
 
diff --git a/tests/managers_regress/tests.py b/tests/managers_regress/tests.py
index 3798b91ef5..11ad52ce44 100644
--- a/tests/managers_regress/tests.py
+++ b/tests/managers_regress/tests.py
@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
 import copy
 
+from django.apps.cache import cache
 from django.db import models
-from django.db.models.loading import cache
 from django.template import Context, Template
 from django.test import TestCase
 from django.test.utils import override_settings
diff --git a/tests/migrations/models.py b/tests/migrations/models.py
index 3bb50289be..9726e4457a 100644
--- a/tests/migrations/models.py
+++ b/tests/migrations/models.py
@@ -1,8 +1,8 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.utils.encoding import python_2_unicode_compatible
 
 
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 48fb68b03d..fa8a212533 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -6,8 +6,8 @@ import copy
 import os
 import shutil
 
+from django.apps.cache import cache
 from django.core.management import call_command, CommandError
-from django.db.models.loading import cache
 from django.test.utils import override_settings
 from django.utils import six
 from django.utils._os import upath
diff --git a/tests/migrations/test_state.py b/tests/migrations/test_state.py
index 9cbbbf294d..13e575862d 100644
--- a/tests/migrations/test_state.py
+++ b/tests/migrations/test_state.py
@@ -1,7 +1,7 @@
-from django.test import TestCase
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.db.migrations.state import ProjectState, ModelState, InvalidBasesError
+from django.test import TestCase
 
 
 class StateTests(TestCase):
diff --git a/tests/migrations/test_writer.py b/tests/migrations/test_writer.py
index 0d64d40350..11109c8186 100644
--- a/tests/migrations/test_writer.py
+++ b/tests/migrations/test_writer.py
@@ -6,10 +6,10 @@ import copy
 import datetime
 import os
 
+from django.apps.cache import cache
 from django.core.validators import RegexValidator, EmailValidator
 from django.db import models, migrations
 from django.db.migrations.writer import MigrationWriter
-from django.db.models.loading import cache
 from django.test import TestCase, override_settings
 from django.utils import six
 from django.utils.deconstruct import deconstructible
diff --git a/tests/proxy_model_inheritance/tests.py b/tests/proxy_model_inheritance/tests.py
index 9941506303..af22e7caed 100644
--- a/tests/proxy_model_inheritance/tests.py
+++ b/tests/proxy_model_inheritance/tests.py
@@ -3,9 +3,9 @@ from __future__ import unicode_literals
 import os
 import sys
 
+from django.apps.cache import cache, load_app
 from django.conf import settings
 from django.core.management import call_command
-from django.db.models.loading import cache, load_app
 from django.test import TestCase, TransactionTestCase
 from django.test.utils import override_settings
 from django.utils._os import upath
diff --git a/tests/proxy_models/tests.py b/tests/proxy_models/tests.py
index 8be7929ac4..a900366744 100644
--- a/tests/proxy_models/tests.py
+++ b/tests/proxy_models/tests.py
@@ -1,13 +1,13 @@
 from __future__ import unicode_literals
 import copy
 
+from django.apps.cache import cache
 from django.contrib import admin
 from django.contrib.contenttypes.models import ContentType
 from django.core import management
 from django.core.exceptions import FieldError
 from django.db import models, DEFAULT_DB_ALIAS
 from django.db.models import signals
-from django.db.models.loading import cache
 from django.test import TestCase
 from django.test.utils import override_settings
 
diff --git a/tests/runtests.py b/tests/runtests.py
index f37c0e9dda..8bcb06e522 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -80,14 +80,14 @@ def get_test_modules():
 
 
 def get_installed():
-    from django.db.models.loading import get_apps
+    from django.apps.cache import get_apps
     return [app.__name__.rsplit('.', 1)[0] for app in get_apps()]
 
 
 def setup(verbosity, test_labels):
     import django
+    from django.apps.cache import get_apps, load_app
     from django.conf import settings
-    from django.db.models.loading import get_apps, load_app
     from django.test import TransactionTestCase, TestCase
 
     print("Testing against Django installed in '%s'" % os.path.dirname(django.__file__))
diff --git a/tests/schema/models.py b/tests/schema/models.py
index 06ba8fb760..2df97b935c 100644
--- a/tests/schema/models.py
+++ b/tests/schema/models.py
@@ -1,5 +1,5 @@
+from django.apps.cache import BaseAppCache
 from django.db import models
-from django.db.models.loading import BaseAppCache
 
 # Because we want to test creation and deletion of these as separate things,
 # these models are all inserted into a separate AppCache so the main test
diff --git a/tests/swappable_models/tests.py b/tests/swappable_models/tests.py
index 85484615a3..ae42366745 100644
--- a/tests/swappable_models/tests.py
+++ b/tests/swappable_models/tests.py
@@ -2,10 +2,10 @@ from __future__ import unicode_literals
 
 from django.utils.six import StringIO
 
+from django.apps.cache import cache
 from django.contrib.auth.models import Permission
 from django.contrib.contenttypes.models import ContentType
 from django.core import management
-from django.db.models.loading import cache
 from django.test import TestCase
 from django.test.utils import override_settings
 
diff --git a/tests/tablespaces/tests.py b/tests/tablespaces/tests.py
index 6a81643a0c..0ee1b0e742 100644
--- a/tests/tablespaces/tests.py
+++ b/tests/tablespaces/tests.py
@@ -2,9 +2,9 @@ from __future__ import unicode_literals
 
 import copy
 
+from django.apps.cache import cache
 from django.conf import settings
 from django.db import connection
-from django.db.models.loading import cache
 from django.core.management.color import no_style
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
 
diff --git a/tests/validation/test_unique.py b/tests/validation/test_unique.py
index b3d389e4ec..995949fed7 100644
--- a/tests/validation/test_unique.py
+++ b/tests/validation/test_unique.py
@@ -3,9 +3,9 @@ from __future__ import unicode_literals
 import datetime
 import unittest
 
+from django.apps.cache import BaseAppCache
 from django.core.exceptions import ValidationError
 from django.db import models
-from django.db.models.loading import BaseAppCache
 from django.test import TestCase
 
 from .models import (CustomPKModel, UniqueTogetherModel, UniqueFieldsModel,