Fixed #21829 -- Added default AppConfigs.

Thanks Russell for the report, Marc for the initial patch, Carl for the
final review, and everyone who contributed to the design discussion.

36 files changed, 188 insertions, 105 deletions

diff --git a/django/apps/base.py b/django/apps/base.py
index ea28797108..2ae40e2454 100644
--- a/django/apps/base.py
+++ b/django/apps/base.py
@@ -61,13 +61,12 @@ class AppConfig(object):
         Factory that creates an app config from an entry in INSTALLED_APPS.
         """
         try:
-            # If import_module succeeds, entry is a path to an app module.
+            # If import_module succeeds, entry is a path to an app module,
+            # which may specify an app config class with default_app_config.
             # Otherwise, entry is a path to an app config class or an error.
             module = import_module(entry)
 
         except ImportError:
-            # Avoid django.utils.module_loading.import_by_path because it
-            # masks errors -- it reraises ImportError as ImproperlyConfigured.
             mod_path, _, cls_name = entry.rpartition('.')
 
             # Raise the original exception when entry cannot be a path to an
@@ -75,39 +74,51 @@ class AppConfig(object):
             if not mod_path:
                 raise
 
-            mod = import_module(mod_path)
+        else:
             try:
-                cls = getattr(mod, cls_name)
+                # If this works, the app module specifies an app config class.
+                entry = module.default_app_config
             except AttributeError:
-                # Emulate the error that "from <mod_path> import <cls_name>"
-                # would raise when <mod_path> exists but not <cls_name>, with
-                # more context (Python just says "cannot import name ...").
-                raise ImportError(
-                    "cannot import name '%s' from '%s'" % (cls_name, mod_path))
+                # Otherwise, it simply uses the default app config class.
+                return cls(entry, module)
+            else:
+                mod_path, _, cls_name = entry.rpartition('.')
 
-            # Check for obvious errors. (This check prevents duck typing, but
-            # it could be removed if it became a problem in practice.)
-            if not issubclass(cls, AppConfig):
-                raise ImproperlyConfigured(
-                    "'%s' isn't a subclass of AppConfig." % entry)
+        # If we're reaching this point, we must load the app config class
+        # located at <mod_path>.<cls_name>.
 
-            # Obtain app name here rather than in AppClass.__init__ to keep
-            # all error checking for entries in INSTALLED_APPS in one place.
-            try:
-                app_name = cls.name
-            except AttributeError:
-                raise ImproperlyConfigured(
-                    "'%s' must supply a name attribute." % entry)
+        # Avoid django.utils.module_loading.import_by_path because it
+        # masks errors -- it reraises ImportError as ImproperlyConfigured.
+        mod = import_module(mod_path)
+        try:
+            cls = getattr(mod, cls_name)
+        except AttributeError:
+            # Emulate the error that "from <mod_path> import <cls_name>"
+            # would raise when <mod_path> exists but not <cls_name>, with
+            # more context (Python just says "cannot import name ...").
+            raise ImportError(
+                "cannot import name '%s' from '%s'" % (cls_name, mod_path))
 
-            # Ensure app_name points to a valid module.
-            app_module = import_module(app_name)
+        # Check for obvious errors. (This check prevents duck typing, but
+        # it could be removed if it became a problem in practice.)
+        if not issubclass(cls, AppConfig):
+            raise ImproperlyConfigured(
+                "'%s' isn't a subclass of AppConfig." % entry)
 
-            # Entry is a path to an app config class.
-            return cls(app_name, app_module)
+        # Obtain app name here rather than in AppClass.__init__ to keep
+        # all error checking for entries in INSTALLED_APPS in one place.
+        try:
+            app_name = cls.name
+        except AttributeError:
+            raise ImproperlyConfigured(
+                "'%s' must supply a name attribute." % entry)
+
+        # Ensure app_name points to a valid module.
+        app_module = import_module(app_name)
+
+        # Entry is a path to an app config class.
+        return cls(app_name, app_module)
 
-        else:
-            # Entry is a path to an app module.
-            return cls(entry, module)
 
     def get_model(self, model_name):
         """
diff --git a/django/conf/project_template/project_name/settings.py b/django/conf/project_template/project_name/settings.py
index 198a3e0d92..efe8091e81 100644
--- a/django/conf/project_template/project_name/settings.py
+++ b/django/conf/project_template/project_name/settings.py
@@ -30,7 +30,7 @@ ALLOWED_HOSTS = []
 # Application definition
 
 INSTALLED_APPS = (
-    'django.contrib.admin.apps.AdminConfig',
+    'django.contrib.admin',
     'django.contrib.auth',
     'django.contrib.contenttypes',
     'django.contrib.sessions',
diff --git a/django/contrib/admin/__init__.py b/django/contrib/admin/__init__.py
index 530badf1df..2218dfd23f 100644
--- a/django/contrib/admin/__init__.py
+++ b/django/contrib/admin/__init__.py
@@ -1,6 +1,5 @@
 # ACTION_CHECKBOX_NAME is unused, but should stay since its import from here
 # has been referenced in documentation.
-from django.contrib.admin.checks import check_admin_app
 from django.contrib.admin.decorators import register
 from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME
 from django.contrib.admin.options import ModelAdmin, HORIZONTAL, VERTICAL
@@ -9,7 +8,6 @@ from django.contrib.admin.filters import (ListFilter, SimpleListFilter,
     FieldListFilter, BooleanFieldListFilter, RelatedFieldListFilter,
     ChoicesFieldListFilter, DateFieldListFilter, AllValuesFieldListFilter)
 from django.contrib.admin.sites import AdminSite, site
-from django.core import checks
 from django.utils.module_loading import autodiscover_modules
 
 __all__ = [
@@ -24,4 +22,5 @@ __all__ = [
 def autodiscover():
     autodiscover_modules('admin', register_to=site)
 
-checks.register('admin')(check_admin_app)
+
+default_app_config = 'django.contrib.admin.apps.AdminConfig'
diff --git a/django/contrib/admin/apps.py b/django/contrib/admin/apps.py
index a8f0e91ea6..93dab8a787 100644
--- a/django/contrib/admin/apps.py
+++ b/django/contrib/admin/apps.py
@@ -1,11 +1,22 @@
 from django.apps import AppConfig
-
+from django.core import checks
+from django.contrib.admin.checks import check_admin_app
 from django.utils.translation import ugettext_lazy as _
 
 
-class AdminConfig(AppConfig):
+class SimpleAdminConfig(AppConfig):
+    """Simple AppConfig which does not do automatic discovery."""
+
     name = 'django.contrib.admin'
     verbose_name = _("administration")
 
     def ready(self):
+        checks.register('admin')(check_admin_app)
+
+
+class AdminConfig(SimpleAdminConfig):
+    """The default AppConfig for admin which does autodiscovery."""
+
+    def ready(self):
+        super(AdminConfig, self).ready()
         self.module.autodiscover()
diff --git a/django/contrib/admin/sites.py b/django/contrib/admin/sites.py
index ba7c38dcad..f25055baf7 100644
--- a/django/contrib/admin/sites.py
+++ b/django/contrib/admin/sites.py
@@ -161,7 +161,7 @@ class AdminSite(object):
         installed, as well as the auth context processor.
         """
         if not apps.is_installed('django.contrib.admin'):
-            raise ImproperlyConfigured("Put 'django.contrib.admin.apps.AdminConfig' in "
+            raise ImproperlyConfigured("Put 'django.contrib.admin' in "
                 "your INSTALLED_APPS setting in order to use the admin application.")
         if not apps.is_installed('django.contrib.contenttypes'):
             raise ImproperlyConfigured("Put 'django.contrib.contenttypes' in "
diff --git a/django/contrib/admindocs/__init__.py b/django/contrib/admindocs/__init__.py
index e69de29bb2..733519ac54 100644
--- a/django/contrib/admindocs/__init__.py
+++ b/django/contrib/admindocs/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.admindocs.apps.AdminDocsConfig'
diff --git a/django/contrib/auth/__init__.py b/django/contrib/auth/__init__.py
index 24c870dafe..77b2482e31 100644
--- a/django/contrib/auth/__init__.py
+++ b/django/contrib/auth/__init__.py
@@ -2,8 +2,6 @@ import inspect
 import re
 
 from django.conf import settings
-from django.contrib.auth.checks import check_user_model
-from django.core import checks
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.utils.module_loading import import_by_path
 from django.middleware.csrf import rotate_token
@@ -15,10 +13,6 @@ BACKEND_SESSION_KEY = '_auth_user_backend'
 REDIRECT_FIELD_NAME = 'next'
 
 
-# Register the user model checks
-checks.register('models')(check_user_model)
-
-
 def load_backend(path):
     return import_by_path(path)()
 
@@ -164,3 +158,6 @@ def get_permission_codename(action, opts):
     Returns the codename of the permission for the specified action.
     """
     return '%s_%s' % (action, opts.model_name)
+
+
+default_app_config = 'django.contrib.auth.apps.AuthConfig'
diff --git a/django/contrib/auth/apps.py b/django/contrib/auth/apps.py
index e44ad1a0c7..a0389acabe 100644
--- a/django/contrib/auth/apps.py
+++ b/django/contrib/auth/apps.py
@@ -1,4 +1,6 @@
 from django.apps import AppConfig
+from django.core import checks
+from django.contrib.auth.checks import check_user_model
 
 from django.utils.translation import ugettext_lazy as _
 
@@ -6,3 +8,6 @@ from django.utils.translation import ugettext_lazy as _
 class AuthConfig(AppConfig):
     name = 'django.contrib.auth'
     verbose_name = _("authentication and authorization")
+
+    def ready(self):
+        checks.register('models')(check_user_model)
diff --git a/django/contrib/comments/__init__.py b/django/contrib/comments/__init__.py
index 19dd7ef9a1..a62fff1b56 100644
--- a/django/contrib/comments/__init__.py
+++ b/django/contrib/comments/__init__.py
@@ -1,6 +1,6 @@
 from importlib import import_module
 import warnings
-from django.apps import apps
+from django.apps import apps as django_apps
 from django.conf import settings
 from django.core import urlresolvers
 from django.core.exceptions import ImproperlyConfigured
@@ -16,7 +16,7 @@ def get_comment_app():
     Get the comment app (i.e. "django.contrib.comments") as defined in the settings
     """
     try:
-        app_config = apps.get_app_config(get_comment_app_name().rpartition(".")[2])
+        app_config = django_apps.get_app_config(get_comment_app_name().rpartition(".")[2])
     except LookupError:
         raise ImproperlyConfigured("The COMMENTS_APP (%r) "
                                    "must be in INSTALLED_APPS" % settings.COMMENTS_APP)
@@ -85,3 +85,6 @@ def get_approve_url(comment):
     else:
         return urlresolvers.reverse("django.contrib.comments.views.moderation.approve",
                                     args=(comment.id,))
+
+
+default_app_config = 'django.contrib.comments.apps.CommentsConfig'
diff --git a/django/contrib/contenttypes/__init__.py b/django/contrib/contenttypes/__init__.py
index 5a04849f06..9789f36eff 100644
--- a/django/contrib/contenttypes/__init__.py
+++ b/django/contrib/contenttypes/__init__.py
@@ -1,8 +1 @@
-# -*- coding: utf-8 -*-
-from __future__ import unicode_literals
-
-from django.contrib.contenttypes.checks import check_generic_foreign_keys
-from django.core import checks
-
-
-checks.register('models')(check_generic_foreign_keys)
+default_app_config = 'django.contrib.contenttypes.apps.ContentTypesConfig'
diff --git a/django/contrib/contenttypes/apps.py b/django/contrib/contenttypes/apps.py
index 0e55e8d66d..4e515d8a00 100644
--- a/django/contrib/contenttypes/apps.py
+++ b/django/contrib/contenttypes/apps.py
@@ -1,8 +1,12 @@
 from django.apps import AppConfig
-
+from django.contrib.contenttypes.checks import check_generic_foreign_keys
+from django.core import checks
 from django.utils.translation import ugettext_lazy as _
 
 
 class ContentTypesConfig(AppConfig):
     name = 'django.contrib.contenttypes'
     verbose_name = _("content types")
+
+    def ready(self):
+        checks.register('models')(check_generic_foreign_keys)
diff --git a/django/contrib/flatpages/__init__.py b/django/contrib/flatpages/__init__.py
index e69de29bb2..865acd855b 100644
--- a/django/contrib/flatpages/__init__.py
+++ b/django/contrib/flatpages/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.flatpages.apps.FlatPagesConfig'
diff --git a/django/contrib/formtools/__init__.py b/django/contrib/formtools/__init__.py
index e69de29bb2..b82588d8e7 100644
--- a/django/contrib/formtools/__init__.py
+++ b/django/contrib/formtools/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.formtools.apps.FormToolsConfig'
diff --git a/django/contrib/gis/__init__.py b/django/contrib/gis/__init__.py
index c996fdfdc2..84b3552ce7 100644
--- a/django/contrib/gis/__init__.py
+++ b/django/contrib/gis/__init__.py
@@ -4,3 +4,6 @@ if six.PY3:
     memoryview = memoryview
 else:
     memoryview = buffer
+
+
+default_app_config = 'django.contrib.gis.apps.GISConfig'
diff --git a/django/contrib/humanize/__init__.py b/django/contrib/humanize/__init__.py
index e69de29bb2..9ca1642fae 100644
--- a/django/contrib/humanize/__init__.py
+++ b/django/contrib/humanize/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.humanize.apps.HumanizeConfig'
diff --git a/django/contrib/messages/__init__.py b/django/contrib/messages/__init__.py
index 40ba6ea6c7..a0cb24b2d9 100644
--- a/django/contrib/messages/__init__.py
+++ b/django/contrib/messages/__init__.py
@@ -1,2 +1,5 @@
 from django.contrib.messages.api import *  # NOQA
 from django.contrib.messages.constants import *  # NOQA
+
+
+default_app_config = 'django.contrib.messages.apps.MessagesConfig'
diff --git a/django/contrib/redirects/__init__.py b/django/contrib/redirects/__init__.py
index e69de29bb2..65364a440b 100644
--- a/django/contrib/redirects/__init__.py
+++ b/django/contrib/redirects/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.redirects.apps.RedirectsConfig'
diff --git a/django/contrib/sessions/__init__.py b/django/contrib/sessions/__init__.py
index e69de29bb2..0382f95d7e 100644
--- a/django/contrib/sessions/__init__.py
+++ b/django/contrib/sessions/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.sessions.apps.SessionsConfig'
diff --git a/django/contrib/sitemaps/__init__.py b/django/contrib/sitemaps/__init__.py
index 4396708098..ee3d22090d 100644
--- a/django/contrib/sitemaps/__init__.py
+++ b/django/contrib/sitemaps/__init__.py
@@ -133,3 +133,6 @@ class GenericSitemap(Sitemap):
         if self.date_field is not None:
             return getattr(item, self.date_field)
         return None
+
+
+default_app_config = 'django.contrib.sitemaps.apps.SiteMapsConfig'
diff --git a/django/contrib/sites/__init__.py b/django/contrib/sites/__init__.py
index e69de29bb2..b554240bb2 100644
--- a/django/contrib/sites/__init__.py
+++ b/django/contrib/sites/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.sites.apps.SitesConfig'
diff --git a/django/contrib/staticfiles/__init__.py b/django/contrib/staticfiles/__init__.py
index e69de29bb2..8a07b83d2f 100644
--- a/django/contrib/staticfiles/__init__.py
+++ b/django/contrib/staticfiles/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.staticfiles.apps.StaticFilesConfig'
diff --git a/django/contrib/syndication/__init__.py b/django/contrib/syndication/__init__.py
index e69de29bb2..2c3f52578d 100644
--- a/django/contrib/syndication/__init__.py
+++ b/django/contrib/syndication/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.syndication.apps.SyndicationConfig'
diff --git a/django/contrib/webdesign/__init__.py b/django/contrib/webdesign/__init__.py
index e69de29bb2..2340116bc8 100644
--- a/django/contrib/webdesign/__init__.py
+++ b/django/contrib/webdesign/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'django.contrib.webdesign.apps.WebDesignConfig'
diff --git a/django/core/checks/registry.py b/django/core/checks/registry.py
index efb5b4b892..21efbf317e 100644
--- a/django/core/checks/registry.py
+++ b/django/core/checks/registry.py
@@ -29,7 +29,8 @@ class CheckRegistry(object):
 
         def inner(check):
             check.tags = tags
-            self.registered_checks.append(check)
+            if check not in self.registered_checks:
+                self.registered_checks.append(check)
             return check
 
         return inner
diff --git a/docs/intro/tutorial01.txt b/docs/intro/tutorial01.txt
index 1bf11e47ae..16b2596da9 100644
--- a/docs/intro/tutorial01.txt
+++ b/docs/intro/tutorial01.txt
@@ -435,7 +435,7 @@ look like this:
     :filename: mysite/settings.py
 
     INSTALLED_APPS = (
-        'django.contrib.admin.apps.AdminConfig',
+        'django.contrib.admin',
         'django.contrib.auth',
         'django.contrib.contenttypes',
         'django.contrib.sessions',
@@ -444,13 +444,6 @@ look like this:
         'polls',
     )
 
-.. admonition:: Doesn't match what you see?
-
-    If you're seeing ``'django.contrib.admin'`` instead of
-    ``'django.contrib.admin.apps.AdminConfig'``, you're probably using a
-    version of Django that doesn't match this tutorial version.  You'll want
-    to either switch to the older tutorial or the newer Django version.
-
 Now Django knows to include the ``polls`` app. Let's run another command:
 
 .. code-block:: bash
diff --git a/docs/ref/applications.txt b/docs/ref/applications.txt
index e496f24487..33f885e416 100644
--- a/docs/ref/applications.txt
+++ b/docs/ref/applications.txt
@@ -49,9 +49,15 @@ Configuring applications
 To configure an application, subclass :class:`~django.apps.AppConfig` and put
 the dotted path to that subclass in :setting:`INSTALLED_APPS`.
 
-Django uses the default :class:`~django.apps.AppConfig` class when
-:setting:`INSTALLED_APPS` simply contains the dotted path to an application
-module.
+When :setting:`INSTALLED_APPS` simply contains the dotted path to an
+application module, Django checks for a ``default_app_config`` variable in
+that module.
+
+If it's defined, it's the dotted path to the :class:`~django.apps.AppConfig`
+subclass for that application.
+
+If there is no ``default_app_config``, Django uses the base
+:class:`~django.apps.AppConfig` class.
 
 For application authors
 -----------------------
@@ -67,8 +73,23 @@ would provide a proper name for the admin::
         name = 'rock_n_roll'
         verbose_name = "Rock ’n’ roll"
 
-You would then tell your users to add ``'rock_n_roll.apps.RockNRollConfig'``
-to their :setting:`INSTALLED_APPS`.
+You can make your application load this :class:`~django.apps.AppConfig`
+subclass by default as follows::
+
+    # rock_n_roll/__init__.py
+
+    default_app_config = 'rock_n_roll.apps.RockNRollConfig'
+
+That will cause ``RockNRollConfig`` to be used when :setting:`INSTALLED_APPS`
+just contains ``'rock_n_roll'``. This allows you to make use of
+:class:`~django.apps.AppConfig` features without requiring your users to
+update their :setting:`INSTALLED_APPS` setting.
+
+Of course, you can also tell your users to put
+``'rock_n_roll.apps.RockNRollConfig'`` in their :setting:`INSTALLED_APPS`
+setting. You can even provide several different
+:class:`~django.apps.AppConfig` subclasses with different behaviors and allow
+your users to choose one via their :setting:`INSTALLED_APPS` setting.
 
 The recommended convention is to put the configuration class in a submodule of
 the application called ``apps``. However, this isn't enforced by Django.
@@ -87,7 +108,7 @@ configuration::
 
     # anthology/apps.py
 
-    from rock_n_roll.app import RockNRollConfig
+    from rock_n_roll.apps import RockNRollConfig
 
     class GypsyJazzConfig(RockNRollConfig):
         verbose_name = "Gypsy jazz"
@@ -213,7 +234,7 @@ Application registry
 .. method:: apps.is_installed(app_name)
 
     Checks whether an application with the given name exists in the registry.
-    ``app_name`` is the full name of the app, e.g. 'django.contrib.admin'.
+    ``app_name`` is the full name of the app, e.g. ``'django.contrib.admin'``.
 
     Unlike :meth:`~django.apps.apps.get_app_config`, this method can be called
     safely at import time. If the registry is still being populated, it may
diff --git a/docs/ref/contrib/admin/index.txt b/docs/ref/contrib/admin/index.txt
index 7fc34c96de..281ea4674b 100644
--- a/docs/ref/contrib/admin/index.txt
+++ b/docs/ref/contrib/admin/index.txt
@@ -23,12 +23,7 @@ The admin is enabled in the default project template used by
 
 For reference, here are the requirements:
 
-1. Add ``'django.contrib.admin.apps.AdminConfig'`` to your
-   :setting:`INSTALLED_APPS` setting.
-
-   .. versionchanged:: 1.7
-
-       :setting:`INSTALLED_APPS` used to contain ``'django.contrib.admin'``.
+1. Add ``'django.contrib.admin'`` to your :setting:`INSTALLED_APPS` setting.
 
 2. The admin has four dependencies - :mod:`django.contrib.auth`,
    :mod:`django.contrib.contenttypes`,
@@ -136,16 +131,23 @@ The register decorator
 Discovery of admin files
 ------------------------
 
-The admin needs to be instructed to look for ``admin.py`` files in your project.
-The easiest solution is to put ``'django.contrib.admin.apps.AdminConfig'`` in
-your :setting:`INSTALLED_APPS` setting.
+When you put ``'django.contrib.admin'`` in your :setting:`INSTALLED_APPS`
+setting, Django automatically looks for an ``admin`` module in each
+application and imports it.
 
 .. class:: apps.AdminConfig
 
     .. versionadded:: 1.7
 
-    This class calls :func:`~django.contrib.admin.autodiscover()` when Django
-    starts.
+    This is the default :class:`~django.apps.AppConfig` class for the admin.
+    It calls :func:`~django.contrib.admin.autodiscover()` when Django starts.
+
+.. class:: apps.SimpleAdminConfig
+
+    .. versionadded:: 1.7
+
+    This class works like :class:`~django.contrib.admin.apps.AdminConfig`,
+    except it doesn't call :func:`~django.contrib.admin.autodiscover()`.
 
 .. function:: autodiscover
 
@@ -155,13 +157,23 @@ your :setting:`INSTALLED_APPS` setting.
     .. versionchanged:: 1.7
 
         Previous versions of Django recommended calling this function directly
-        in the URLconf. :class:`~django.contrib.admin.apps.AdminConfig`
-        replaces that mechanism and is more robust.
+        in the URLconf. As of Django 1.7 this isn't needed anymore.
+        :class:`~django.contrib.admin.apps.AdminConfig` takes care of running
+        the auto-discovery automatically.
 
 If you are using a custom ``AdminSite``, it is common to import all of the
 ``ModelAdmin`` subclasses into your code and register them to the custom
-``AdminSite``. In that case, simply put ``'django.contrib.admin'`` in your
-:setting:`INSTALLED_APPS` setting, as you don't need autodiscovery.
+``AdminSite``. In that case, in order to disable auto-discovery, you should
+put ``'django.contrib.admin.apps.SimpleAdminConfig'`` instead of
+``'django.contrib.admin'`` in your :setting:`INSTALLED_APPS` setting.
+
+.. versionchanged:: 1.7
+
+    In previous versions, the admin needed to be instructed to look for
+    ``admin.py`` files with :func:`~django.contrib.admin.autodiscover()`.
+    As of Django 1.7, auto-discovery is enabled by default and must be
+    explicitly disabled when it's undesirable.
+
 
 ``ModelAdmin`` options
 ----------------------
@@ -2426,11 +2438,12 @@ In this example, we register the ``AdminSite`` instance
         (r'^myadmin/', include(admin_site.urls)),
     )
 
-Note that you don't need autodiscovery of ``admin`` modules when using your
+Note that you may not want autodiscovery of ``admin`` modules when using your
 own ``AdminSite`` instance since you will likely be importing all the per-app
-``admin`` modules in your ``myproject.admin`` module. This means you likely do
-not need ``'django.contrib.admin.app.AdminConfig'`` in your
-:setting:`INSTALLED_APPS` and can just use ``'django.contrib.admin'``.
+``admin`` modules in your ``myproject.admin`` module. This means you need to
+put ``'django.contrib.admin.app.SimpleAdminConfig'`` instead of
+``'django.contrib.admin'`` in your :setting:`INSTALLED_APPS` setting.
+
 
 Multiple admin sites in the same URLconf
 ----------------------------------------
diff --git a/docs/ref/contrib/gis/tutorial.txt b/docs/ref/contrib/gis/tutorial.txt
index f3eeb64e59..ff27c9b6ec 100644
--- a/docs/ref/contrib/gis/tutorial.txt
+++ b/docs/ref/contrib/gis/tutorial.txt
@@ -115,7 +115,7 @@ In addition, modify the :setting:`INSTALLED_APPS` setting to include
 and ``world`` (your newly created application)::
 
     INSTALLED_APPS = (
-        'django.contrib.admin.apps.AdminConfig',
+        'django.contrib.admin',
         'django.contrib.auth',
         'django.contrib.contenttypes',
         'django.contrib.sessions',
diff --git a/docs/releases/1.7.txt b/docs/releases/1.7.txt
index df115c6c15..684daa988c 100644
--- a/docs/releases/1.7.txt
+++ b/docs/releases/1.7.txt
@@ -89,17 +89,14 @@ Improvements thus far include:
 * The name of applications can be customized in the admin with the
   :attr:`~django.apps.AppConfig.verbose_name` of application configurations.
 
+* The admin automatically calls :func:`~django.contrib.admin.autodiscover()`
+  when Django starts. You can consequently remove this line from your
+  URLconf.
+
 * Django imports all application configurations and models as soon as it
   starts, through a deterministic and straightforward process. This should
   make it easier to diagnose import issues such as import loops.
 
-* The admin has an :class:`~django.contrib.admin.apps.AdminConfig` application
-  configuration class. When Django starts, this class takes care of calling
-  :func:`~django.contrib.admin.autodiscover()`. To use it, simply replace
-  ``'django.contrib.admin'`` in :setting:`INSTALLED_APPS` with
-  ``'django.contrib.admin.apps.AdminConfig'`` and remove
-  ``admin.autodiscover()`` from your URLconf.
-
 New method on Field subclasses
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -698,6 +695,12 @@ regressions cannot be ruled out. You may encounter the following exceptions:
   results. The code will be executed when you first need its results. This
   concept is known as "lazy evaluation".
 
+* ``django.contrib.admin`` will now automatically perform autodiscovery of
+  ``admin`` modules in installed applications. To prevent it, change your
+  :setting:`INSTALLED_APPS` to contain
+  ``'django.contrib.admin.apps.SimpleAdminConfig'`` instead of
+  ``'django.contrib.admin'``.
+
 Standalone scripts
 ^^^^^^^^^^^^^^^^^^
 
diff --git a/docs/topics/auth/default.txt b/docs/topics/auth/default.txt
index bfac4c922e..a721fb548c 100644
--- a/docs/topics/auth/default.txt
+++ b/docs/topics/auth/default.txt
@@ -67,9 +67,8 @@ Creating superusers
 -------------------
 
 :djadmin:`manage.py migrate <migrate>` prompts you to create a superuser the
-first time you run it with ``'django.contrib.auth'`` in your
-:setting:`INSTALLED_APPS`. If you need to create a superuser at a later date,
-you can use a command line utility::
+first time you run it with ``'django.contrib.auth'`` installed. If you need to
+create a superuser at a later date, you can use a command line utility::
 
     $ python manage.py createsuperuser --username=joe --email=joe@example.com
 
diff --git a/tests/admin_scripts/tests.py b/tests/admin_scripts/tests.py
index 225441827f..f1a4d55521 100644
--- a/tests/admin_scripts/tests.py
+++ b/tests/admin_scripts/tests.py
@@ -1113,7 +1113,7 @@ class ManageCheck(AdminScriptTestCase):
             apps=[
                 'admin_scripts.complex_app',
                 'admin_scripts.simple_app',
-                'django.contrib.admin',
+                'django.contrib.admin.apps.SimpleAdminConfig',
                 'django.contrib.auth',
                 'django.contrib.contenttypes',
             ],
diff --git a/tests/apps/default_config_app/__init__.py b/tests/apps/default_config_app/__init__.py
new file mode 100644
index 0000000000..aebe0350d9
--- /dev/null
+++ b/tests/apps/default_config_app/__init__.py
@@ -0,0 +1 @@
+default_app_config = 'apps.default_config_app.apps.CustomConfig'
diff --git a/tests/apps/default_config_app/apps.py b/tests/apps/default_config_app/apps.py
new file mode 100644
index 0000000000..ba859a4750
--- /dev/null
+++ b/tests/apps/default_config_app/apps.py
@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class CustomConfig(AppConfig):
+    name = 'apps.default_config_app'
diff --git a/tests/apps/tests.py b/tests/apps/tests.py
index 139bc06a66..814ef0186f 100644
--- a/tests/apps/tests.py
+++ b/tests/apps/tests.py
@@ -7,6 +7,7 @@ from django.db import models
 from django.test import TestCase, override_settings
 from django.utils import six
 
+from .default_config_app.apps import CustomConfig
 from .models import TotallyNormal, SoAlternative, new_apps
 
 
@@ -82,6 +83,11 @@ class AppsTests(TestCase):
             with self.settings(INSTALLED_APPS=['apps.apps.NoSuchConfig']):
                 pass
 
+    def test_default_app_config(self):
+        with self.settings(INSTALLED_APPS=['apps.default_config_app']):
+            config = apps.get_app_config('default_config_app')
+        self.assertIsInstance(config, CustomConfig)
+
     @override_settings(INSTALLED_APPS=SOME_INSTALLED_APPS)
     def test_get_app_configs(self):
         """
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index 116364790f..fd909e4c51 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -1049,7 +1049,7 @@ class AppResolutionOrderI18NTests(ResolutionOrderI18NTests):
             # Doesn't work because it's added later in the list.
             self.assertUgettext('Date/time', 'Datum/Zeit')
 
-            with self.modify_settings(INSTALLED_APPS={'remove': 'django.contrib.admin'}):
+            with self.modify_settings(INSTALLED_APPS={'remove': 'django.contrib.admin.apps.SimpleAdminConfig'}):
                 self.flush_caches()
                 activate('de')
 
diff --git a/tests/runtests.py b/tests/runtests.py
index 8009136ac3..b2c0837222 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -44,7 +44,7 @@ ALWAYS_INSTALLED_APPS = [
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.comments',
-    'django.contrib.admin',
+    'django.contrib.admin.apps.SimpleAdminConfig',
     'django.contrib.admindocs',
     'django.contrib.staticfiles',
     'django.contrib.humanize',
@@ -168,12 +168,11 @@ def setup(verbosity, test_labels):
                 for label in test_labels_set)
 
         installed_app_names = set(get_installed())
-        if module_found_in_labels:
+        if module_found_in_labels and module_label not in installed_app_names:
             if verbosity >= 2:
                 print("Importing application %s" % module_name)
             # HACK.
-            if module_label not in installed_app_names:
-                settings.INSTALLED_APPS.append(module_label)
+            settings.INSTALLED_APPS.append(module_label)
             app_config = AppConfig.create(module_label)
             apps.app_configs[app_config.label] = app_config
             app_config.import_models(apps.all_models[app_config.label])