From bde1bc66724db34dcde598f064448da1f2a8a810 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?V=C3=AD=C3=B0ir=20Valberg=20Gu=C3=B0mundsson?= Date: Sun, 13 Apr 2014 17:18:02 +0200 Subject: [PATCH] [1.7.x] Fixed #22422 -- Moved information about the application loading process to refs/applications.txt. Backport of deb561bbe2 from master --- docs/ref/applications.txt | 42 +++++++++++++++++++++++++++++++++++++++ docs/releases/1.7.txt | 37 ++-------------------------------- 2 files changed, 44 insertions(+), 35 deletions(-) diff --git a/docs/ref/applications.txt b/docs/ref/applications.txt index ef067c20326..04083de2b94 100644 --- a/docs/ref/applications.txt +++ b/docs/ref/applications.txt @@ -306,3 +306,45 @@ Application registry Raises :exc:`~exceptions.LookupError` if no such application or model exists. Raises :exc:`~exceptions.ValueError` when called with a single argument that doesn't contain exactly one dot. + +.. _application-loading-process: + +Application loading process +=========================== + +Django loads application configurations and models as soon as it starts. Here +are some common problems you may encounter: + +* ``RuntimeError: App registry isn't ready yet.`` This happens when importing + an application configuration or a models module triggers code that depends + on the app registry. + + For example, :func:`~django.utils.translation.ugettext()` uses the app + registry to look up translation catalogs in applications. To translate at + import time, you need :func:`~django.utils.translation.ugettext_lazy()` + instead. (Using :func:`~django.utils.translation.ugettext()` would be a bug, + because the translation would happen at import time, rather than at each + request depending on the active language.) + + Executing database queries with the ORM at import time in models modules + will also trigger this exception. The ORM cannot function properly until all + models are available. + + Another common culprit is :func:`django.contrib.auth.get_user_model()`. Use + the :setting:`AUTH_USER_MODEL` setting to reference the User model at import + time. + +* ``ImportError: cannot import name ...`` This happens if the import sequence + ends up in a loop. + + To eliminate such problems, you should minimize dependencies between your + models modules and do as little work as possible at import time. To avoid + executing code at import time, you can move it into a function and cache its + 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'``. diff --git a/docs/releases/1.7.txt b/docs/releases/1.7.txt index d0fe0a56201..e242d18ae91 100644 --- a/docs/releases/1.7.txt +++ b/docs/releases/1.7.txt @@ -877,41 +877,8 @@ Start-up sequence Django 1.7 loads application configurations and models as soon as it starts. While this behavior is more straightforward and is believed to be more robust, -regressions cannot be ruled out. You may encounter the following exceptions: - -* ``RuntimeError: App registry isn't ready yet.`` This happens when importing - an application configuration or a models module triggers code that depends - on the app registry. - - For example, :func:`~django.utils.translation.ugettext()` uses the app - registry to look up translation catalogs in applications. To translate at - import time, you need :func:`~django.utils.translation.ugettext_lazy()` - instead. (Using :func:`~django.utils.translation.ugettext()` would be a bug, - because the translation would happen at import time, rather than at each - request depending on the active language.) - - Executing database queries with the ORM at import time in models modules - will also trigger this exception. The ORM cannot function properly until all - models are available. - - Another common culprit is :func:`django.contrib.auth.get_user_model()`. Use - the :setting:`AUTH_USER_MODEL` setting to reference the User model at import - time. - -* ``ImportError: cannot import name ...`` This happens if the import sequence - ends up in a loop. - - To eliminate such problems, you should minimize dependencies between your - models modules and do as little work as possible at import time. To avoid - executing code at import time, you can move it into a function and cache its - 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'``. +regressions cannot be ruled out. See :ref:`application-loading-process` for +solutions to some problems you may encounter. Standalone scripts ^^^^^^^^^^^^^^^^^^