django/docs/releases/1.7.txt

============================================
Django 1.7 release notes - UNDER DEVELOPMENT
============================================

Welcome to Django 1.7!

These release notes cover the `new features`_, as well as some `backwards
incompatible changes`_ you'll want to be aware of when upgrading from Django
1.6 or older versions. We've also dropped some features, which are detailed in
:doc:`our deprecation plan </internals/deprecation>`, and we've `begun the
deprecation process for some features`_.

.. _`new features`: `What's new in Django 1.7`_
.. _`backwards incompatible changes`: `Backwards incompatible changes in 1.7`_
.. _`begun the deprecation process for some features`: `Features deprecated in 1.7`_

Python compatibility
====================

Django 1.7 requires Python 2.7 or above, though we **highly recommend**
the latest minor release. Support for Python 2.6 has been dropped.

This change should affect only a small number of Django users, as most
operating-system vendors today are shipping Python 2.7 or newer as their default
version. If you're still using Python 2.6, however, you'll need to stick to
Django 1.6 until you can upgrade your Python version. Per :doc:`our support
policy </internals/release-process>`, Django 1.6 will continue to receive
security support until the release of Django 1.8.

What's new in Django 1.7
========================

Schema migrations
~~~~~~~~~~~~~~~~~

Django now has built-in support for schema migrations. It allows models
to be updated, changed, and deleted by creating migration files that represent
the model changes and which can be run on any development, staging or production
database.

Migrations are covered in :doc:`their own documentation</topics/migrations>`,
but a few of the key features are:

* ``syncdb`` has been deprecated and replaced by ``migrate``. Don't worry -
  calls to ``syncdb`` will still work as before.

* A new ``makemigrations`` command provides an easy way to autodetect changes
  to your models and make migrations for them.

  :data:`~django.db.models.signals.pre_syncdb` and
  :data:`~django.db.models.signals.post_syncdb` have been replaced by
  :data:`~django.db.models.signals.pre_migrate` and
  :data:`~django.db.models.signals.post_migrate` respectively. These new
  signals have slightly different arguments. Check the documentation for
  details.

* The ``allow_syncdb`` method on database routers is now called ``allow_migrate``,
  but still performs the same function. Routers with ``allow_syncdb`` methods
  will still work, but that method name is deprecated and you should change
  it as soon as possible (nothing more than renaming is required).

App-loading refactor
~~~~~~~~~~~~~~~~~~~~

Historically, Django applications were tightly linked to models. A singleton
known as the "app cache" dealt with both installed applications and models.
The models module was used as an identifier for applications in many APIs.

As the concept of :doc:`Django applications </ref/applications>` matured, this
code showed some shortcomings. It has been refactored into an "app registry"
where models modules no longer have a central role and where it's possible to
attach configuration data to applications.

Improvements thus far include:

* Applications can run code at startup, before Django does anything else, with
  the :meth:`~django.apps.AppConfig.ready` method of their configuration.

* Application labels are assigned correctly to models even when they're
  defined outside of ``models.py``. You don't have to set
  :attr:`~django.db.models.Options.app_label` explicitly any more.

* It is possible to omit ``models.py`` entirely if an application doesn't
  have any models.

* Applications can be relabeled with the :attr:`~django.apps.AppConfig.label`
  attribute of application configurations, to work around label conflicts.

* The name of applications can be customized in the admin with the
  :attr:`~django.apps.AppConfig.verbose_name` of application configurations.

* 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.

New method on Field subclasses
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To help power both schema migrations and composite keys, the :class:`~django.db.models.Field` API now
has a new required method: ``deconstruct()``.

This method takes no arguments, and returns a tuple of four items:

* ``name``: The field's attribute name on its parent model, or None if it is not part of a model
* ``path``: A dotted, Python path to the class of this field, including the class name.
* ``args``: Positional arguments, as a list
* ``kwargs``: Keyword arguments, as a dict

These four values allow any field to be serialized into a file, as well as
allowing the field to be copied safely, both essential parts of these new features.

This change should not affect you unless you write custom Field subclasses;
if you do, you may need to reimplement the ``deconstruct()`` method if your
subclass changes the method signature of ``__init__`` in any way. If your
field just inherits from a built-in Django field and doesn't override ``__init__``,
no changes are necessary.

If you do need to override ``deconstruct()``, a good place to start is the
built-in Django fields (``django/db/models/fields/__init__.py``) as several
fields, including ``DecimalField`` and ``DateField``, override it and show how
to call the method on the superclass and simply add or remove extra arguments.

Calling custom ``QuerySet`` methods from the ``Manager``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The :meth:`QuerySet.as_manager() <django.db.models.query.QuerySet.as_manager>`
class method has been added to :ref:`create Manager with QuerySet methods
<create-manager-with-queryset-methods>`.

Using a custom manager when traversing reverse relations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It is now possible to :ref:`specify a custom manager
<using-custom-reverse-manager>` when traversing a reverse relationship.

New ``Prefetch`` object for advanced ``prefetch_related`` operations.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The new :class:`~django.db.models.Prefetch` object allows customizing
prefetch operations.

You can specify the ``QuerySet`` used to traverse a given relation
or customize the storage location of prefetch results.

This enables things like filtering prefetched relations, calling
:meth:`~django.db.models.query.QuerySet.select_related()` from a prefetched
relation, or prefetching the same relation multiple times with different
querysets. See :meth:`~django.db.models.query.QuerySet.prefetch_related()`
for more details.

Admin shortcuts support time zones
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The "today" and "now" shortcuts next to date and time input widgets in the
admin are now operating in the :ref:`current time zone
<default-current-time-zone>`. Previously, they used the browser time zone,
which could result in saving the wrong value when it didn't match the current
time zone on the server.

In addition, the widgets now display a help message when the browser and
server time zone are different, to clarify how the value inserted in the field
will be interpreted.

Using database cursors as context managers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Prior to Python 2.7, database cursors could be used as a context manager. The
specific backend's cursor defined the behavior of the context manager. The
behavior of magic method lookups was changed with Python 2.7 and cursors were
no longer usable as context managers.

Django 1.7 allows a cursor to be used as a context manager that is a shortcut
for the following, instead of backend specific behavior.

.. code-block:: python

    c = connection.cursor()
    try:
        c.execute(...)
    finally:
        c.close()

Custom lookups
~~~~~~~~~~~~~~

It is now possible to write custom lookups and transforms for the ORM.
Custom lookups work just like Django's inbuilt lookups (e.g. ``lte``,
``icontains``) while transforms are a new concept.

The :class:`django.db.models.Lookup` class provides a way to add lookup
operators for model fields. As an example it is possible to add ``day_lte``
opertor for ``DateFields``.

The :class:`django.db.models.Transform` class allows transformations of
database values prior to the final lookup. For example it is possible to
write a ``year`` transform that extracts year from the field's value.
Transforms allow for chaining. After the ``year`` transform has been added
to ``DateField`` it is possible to filter on the transformed value, for
example ``qs.filter(author__birthdate__year__lte=1981)``.

For more information about both custom lookups and transforms refer to
:doc:`custom lookups </ref/models/custom-lookups>` documentation.

Minor features
~~~~~~~~~~~~~~

:mod:`django.contrib.admin`
^^^^^^^^^^^^^^^^^^^^^^^^^^^

* You can now implement :attr:`~django.contrib.admin.AdminSite.site_header`,
  :attr:`~django.contrib.admin.AdminSite.site_title`, and
  :attr:`~django.contrib.admin.AdminSite.index_title` attributes on a custom
  :class:`~django.contrib.admin.AdminSite` in order to easily change the admin
  site's page title and header text. No more needing to override templates!

* Buttons in :mod:`django.contrib.admin` now use the ``border-radius`` CSS
  property for rounded corners rather than GIF background images.

* Some admin templates now have ``app-<app_name>`` and ``model-<model_name>``
  classes in their ``<body>`` tag to allow customizing the CSS per app or per
  model.

* The admin changelist cells now have a ``field-<field_name>`` class in the
  HTML to enable style customizations.

* The admin's search fields can now be customized per-request thanks to the new
  :meth:`django.contrib.admin.ModelAdmin.get_search_fields` method.

* The :meth:`ModelAdmin.get_fields()
  <django.contrib.admin.ModelAdmin.get_fields>` method may be overridden to
  customize the value of :attr:`ModelAdmin.fields
  <django.contrib.admin.ModelAdmin.fields>`.

* In addition to the existing ``admin.site.register`` syntax, you can use the
  new :func:`~django.contrib.admin.register` decorator to register a
  :class:`~django.contrib.admin.ModelAdmin`.

* You may specify :meth:`ModelAdmin.list_display_links
  <django.contrib.admin.ModelAdmin.list_display_links>` ``= None`` to disable
  links on the change list page grid.

* You may now specify :attr:`ModelAdmin.view_on_site
  <django.contrib.admin.ModelAdmin.view_on_site>` to control whether or not to
  display the "View on site" link.

:mod:`django.contrib.auth`
^^^^^^^^^^^^^^^^^^^^^^^^^^

* Any ``**kwargs`` passed to
  :meth:`~django.contrib.auth.models.User.email_user()` are passed to the
  underlying :meth:`~django.core.mail.send_mail()` call.

* The :func:`~django.contrib.auth.decorators.permission_required` decorator can
  take a list of permissions as well as a single permission.

* You can override the new :meth:`AuthenticationForm.confirm_login_allowed()
  <django.contrib.auth.forms.AuthenticationForm.confirm_login_allowed>` method
  to more easily customize the login policy.

* :func:`django.contrib.auth.views.password_reset` takes an optional
  ``html_email_template_name`` parameter used to send a multipart HTML email
  for password resets.

:mod:`django.contrib.gis`
^^^^^^^^^^^^^^^^^^^^^^^^^^

* The default OpenLayers library version included in widgets has been updated
  from 2.11 to 2.13.

* Prepared geometries now also support the ``crosses``, ``disjoint``,
  ``overlaps``, ``touches`` and ``within`` predicates, if GEOS 3.3 or later is
  installed.

:mod:`django.contrib.messages`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The backends for :mod:`django.contrib.messages` that use cookies, will now
  follow the :setting:`SESSION_COOKIE_SECURE` and
  :setting:`SESSION_COOKIE_HTTPONLY` settings.

* The :ref:`messages context processor <message-displaying>` now adds a
  dictionary of default levels under the name ``DEFAULT_MESSAGE_LEVELS``.

* :class:`~django.contrib.messages.storage.base.Message` objects now have a
  ``level_tag`` attribute that contains the string representation of the
  message level.

:mod:`django.contrib.redirects`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* :class:`~django.contrib.redirects.middleware.RedirectFallbackMiddleware`
  has two new attributes
  (:attr:`~django.contrib.redirects.middleware.RedirectFallbackMiddleware.response_gone_class`
  and
  :attr:`~django.contrib.redirects.middleware.RedirectFallbackMiddleware.response_redirect_class`)
  that specify the types of :class:`~django.http.HttpResponse` instances the
  middleware returns.

:mod:`django.contrib.sessions`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The ``"django.contrib.sessions.backends.cached_db"`` session backend now
  respects :setting:`SESSION_CACHE_ALIAS`. In previous versions, it always used
  the `default` cache.

:mod:`django.contrib.sitemaps`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The :mod:`sitemap framework<django.contrib.sitemaps>` now makes use of
  :attr:`~django.contrib.sitemaps.Sitemap.lastmod` to set a ``Last-Modified``
  header in the response. This makes it possible for the
  :class:`~django.middleware.http.ConditionalGetMiddleware` to handle
  conditional ``GET`` requests for sitemaps which set ``lastmod``.

:mod:`django.contrib.staticfiles`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The :ref:`static files storage classes <staticfiles-storages>` may be
  subclassed to override the permissions that collected static files and
  directories receive by setting the
  :attr:`~django.core.files.storage.FileSystemStorage.file_permissions_mode`
  and :attr:`~django.core.files.storage.FileSystemStorage.directory_permissions_mode`
  parameters. See :djadmin:`collectstatic` for example usage.

:mod:`django.contrib.syndication`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The :class:`~django.utils.feedgenerator.Atom1Feed` syndication feed's
  ``updated`` element now utilizes ``updateddate`` instead of ``pubdate``,
  allowing the ``published`` element to be included in the feed (which
  relies on ``pubdate``).

Cache
^^^^^

* Access to caches configured in :setting:`CACHES` is now available via
  :data:`django.core.cache.caches`. This dict-like object provides a different
  instance per thread. It supersedes :func:`django.core.cache.get_cache` which
  is now deprecated.

* If you instanciate cache backends directly, be aware that they aren't
  thread-safe any more, as :data:`django.core.cache.caches` now yields
  different instances per thread.

Email
^^^^^

* :func:`~django.core.mail.send_mail` now accepts an ``html_message``
  parameter for sending a multipart ``text/plain`` and ``text/html`` email.
* The SMTP :class:`~django.core.mail.backends.smtp.EmailBackend` now accepts a
  :attr:`~django.core.mail.backends.smtp.EmailBackend.timeout` parameter.

File Uploads
^^^^^^^^^^^^

* The new :attr:`UploadedFile.content_type_extra
  <django.core.files.uploadedfile.UploadedFile.content_type_extra>` attribute
  contains extra parameters passed to the ``content-type`` header on a file
  upload.

* The new :setting:`FILE_UPLOAD_DIRECTORY_PERMISSIONS` setting controls
  the file system permissions of directories created during file upload, like
  :setting:`FILE_UPLOAD_PERMISSIONS` does for the files themselves.

* The :attr:`FileField.upload_to <django.db.models.FileField.upload_to>`
  attribute is now optional. If it is omitted or given ``None`` or an empty
  string, a subdirectory won't be used for storing the uploaded files.

Forms
^^^^^

* The ``<label>`` and ``<input>`` tags rendered by
  :class:`~django.forms.RadioSelect` and
  :class:`~django.forms.CheckboxSelectMultiple` when looping over the radio
  buttons or checkboxes now include ``for`` and ``id`` attributes, respectively.
  Each radio button or checkbox includes an ``id_for_label`` attribute to
  output the element's ID.

* :attr:`Field.choices<django.db.models.Field.choices>` now allows you to
  customize the "empty choice" label by including a tuple with an empty string
  or ``None`` for the key and the custom label as the value. The default blank
  option ``"----------"`` will be omitted in this case.

* :class:`~django.forms.MultiValueField` allows optional subfields by setting
  the ``require_all_fields`` argument to ``False``. The ``required`` attribute
  for each individual field will be respected, and a new ``incomplete``
  validation error will be raised when any required fields are empty.

* The :meth:`~django.forms.Form.clean` method on a form no longer needs to
  return ``self.cleaned_data``. If it does return a changed dictionary then
  that will still be used.

* After a temporary regression in Django 1.6, it's now possible again to make
  :class:`~django.forms.TypedChoiceField` ``coerce`` method return an arbitrary
  value.

* :attr:`SelectDateWidget.months
  <django.forms.extras.widgets.SelectDateWidget.months>` can be used to
  customize the wording of the months displayed in the select widget.

* The ``min_num`` and ``validate_min`` parameters were added to
  :func:`~django.forms.formsets.formset_factory` to allow validating
  a minimum number of submitted forms.

* The metaclasses used by ``Form`` and ``ModelForm`` have been reworked to
  support more inheritance scenarios. The previous limitation that prevented
  inheriting from both ``Form`` and ``ModelForm`` simultaneously have been
  removed as long as ``ModelForm`` appears first in the MRO.

* It's now possible to opt-out from a ``Form`` field declared in a parent class
  by shadowing it with a non-``Field`` value.

* The new :meth:`~django.forms.Form.add_error()` method allows adding errors
  to specific form fields.

* The dict-like attribute :attr:`~django.forms.Form.errors` now has two new
  methods :meth:`~django.forms.Form.errors.as_data()` and
  :meth:`~django.forms.Form.errors.as_json()`. The former returns a ``dict``
  that maps fields to their original errors, complete with all metadata
  (error code and params), the latter returns the errors serialized as json.

Internationalization
^^^^^^^^^^^^^^^^^^^^

* The :attr:`django.middleware.locale.LocaleMiddleware.response_redirect_class`
  attribute allows you to customize the redirects issued by the middleware.

* The :class:`~django.middleware.locale.LocaleMiddleware` now stores the user's
  selected language with the session key ``_language``. Previously it was
  stored with the key ``django_language``, but keys reserved for Django should
  start with an underscore. For backwards compatibility ``django_language`` is
  still read from in 1.7. Sessions will be migrated to the new ``_language``
  key as they are written.

* The :ttag:`blocktrans` now supports a ``trimmed`` option. This
  option will remove newline characters from the beginning and the end of the
  content of the ``{% blocktrans %}`` tag, replace any whitespace at the
  beginning and end of a line and merge all lines into one using a space
  character to separate them. This is quite useful for indenting the content of
  a ``{% blocktrans %}`` tag without having the indentation characters end up
  in the corresponding entry in the PO file, which makes the translation
  process easier.

* When you run :djadmin:`makemessages` from the root directory of your project,
  any extracted strings will now be automatically distributed to the proper
  app or project message file. See :ref:`how-to-create-language-files` for
  details.

Management Commands
^^^^^^^^^^^^^^^^^^^

* The :djadminopt:`--no-color` option for ``django-admin.py`` allows you to
  disable the colorization of management command output.

* The new :djadminopt:`--natural-foreign` and :djadminopt:`--natural-primary`
  options for :djadmin:`dumpdata`, and the new ``use_natural_foreign_keys`` and
  ``use_natural_primary_keys`` arguments for ``serializers.serialize()``, allow
  the use of natural primary keys when serializing.

* It is no longer necessary to provide the cache table name or the
  :djadminopt:`--database` option for the :djadmin:`createcachetable` command.
  Django takes this information from your settings file. If you have configured
  multiple caches or multiple databases, all cache tables are created.

* The :djadmin:`runserver` command received several improvements:

  * On Linux systems, if pyinotify_ is installed, the development server will
    reload immediately when a file is changed. Previously, it polled the
    filesystem for changes every second. That caused a small delay before
    reloads and reduced battery life on laptops.

    .. _pyinotify: https://pypi.python.org/pypi/pyinotify

  * In addition, the development server automatically reloads when a
    translation file is updated, i.e. after running
    :djadmin:`compilemessages`.

  * All HTTP requests are logged to the console, including requests for static
    files or ``favicon.ico`` that used to be filtered out.

* Management commands can now produce syntax colored output under Windows if
  the ANSICON third-party tool is installed and active.

Models
^^^^^^

* The :meth:`QuerySet.update_or_create()
  <django.db.models.query.QuerySet.update_or_create>` method was added.

* The new :attr:`~django.db.models.Options.default_permissions` model
  ``Meta`` option allows you to customize (or disable) creation of the default
  add, change, and delete permissions.

* Explicit :class:`~django.db.models.OneToOneField` for
  :ref:`multi-table-inheritance` are now discovered in abstract classes.

* Is it now possible to avoid creating a backward relation for
  :class:`~django.db.models.OneToOneField` by setting its
  :attr:`~django.db.models.ForeignKey.related_name` to
  ``'+'`` or ending it with ``'+'``.

* :class:`F expressions <django.db.models.F>` support the power operator
  (``**``).

* The ``remove()`` and ``clear()`` methods of the related managers created by
  ``ForeignKey`` and ``GenericForeignKey`` now accept the ``bulk`` keyword
  argument to control whether or not to perform operations in bulk
  (i.e. using ``QuerySet.update()``). Defaults to ``True``.

* It is now possible to use ``None`` as a query value for the :lookup:`iexact`
  lookup.

Signals
^^^^^^^

* The ``enter`` argument was added to the
  :data:`~django.test.signals.setting_changed` signal.

* The model signals can be now be connected to using a ``str`` of the
  ``'app_label.ModelName'`` form – just like related fields – to lazily
  reference their senders.

Templates
^^^^^^^^^

* The :meth:`Context.push() <django.template.Context.push>` method now returns
  a context manager which automatically calls :meth:`pop()
  <django.template.Context.pop>` upon exiting the ``with`` statement.
  Additionally, :meth:`push() <django.template.Context.push>` now accepts
  parameters that are passed to the ``dict`` constructor used to build the new
  context level.

* The :ttag:`widthratio` template tag now accepts an "as" parameter to capture
  the result in a variable.

* The :ttag:`include` template tag will now also accept anything with a
  ``render()`` method (such as a ``Template``) as an argument. String
  arguments will be looked up using
  :func:`~django.template.loader.get_template` as always.

* It is now possible to :ttag:`include` templates recursively.

* Template objects now have an origin attribute set when
  :setting:`TEMPLATE_DEBUG` is ``True``. This allows template origins to be
  inspected and logged outside of the ``django.template`` infrastructure.

* ``TypeError`` exceptions are no longer silenced when raised during the
  rendering of a template.

* The following functions now accept a ``dirs`` parameter which is a list or
  tuple to override :setting:`TEMPLATE_DIRS`:

  * :func:`django.template.loader.get_template()`
  * :func:`django.template.loader.select_template()`
  * :func:`django.shortcuts.render()`
  * :func:`django.shortcuts.render_to_response()`

* The :tfilter:`time` filter now accepts timzone-related :ref:`format
  specifiers <date-and-time-formatting-specifiers>` ``'e'``, ``'O'`` , ``'T'``
  and ``'Z'`` and is able to digest :ref:`time-zone-aware
  <naive_vs_aware_datetimes>` ``datetime`` instances performing the expected
  rendering.

* The :ttag:`cache` tag will now try to use the cache called
  "template_fragments" if it exists and fall back to using the default cache
  otherwise. It also now accepts an optional ``using`` keyword argument to
  control which cache it uses.

Requests
^^^^^^^^

* The new :attr:`HttpRequest.scheme <django.http.HttpRequest.scheme>` attribute
  specifies the scheme of the request (``http`` or ``https`` normally).

Tests
^^^^^

* :class:`~django.test.runner.DiscoverRunner` has two new attributes,
  :attr:`~django.test.runner.DiscoverRunner.test_suite` and
  :attr:`~django.test.runner.DiscoverRunner.test_runner`, which facilitate
  overriding the way tests are collected and run.

* The ``fetch_redirect_response`` argument was added to
  :meth:`~django.test.SimpleTestCase.assertRedirects`. Since the test
  client can't fetch externals URLs, this allows you to use ``assertRedirects``
  with redirects that aren't part of your Django app.

* Correct handling of scheme when making comparisons in
  :meth:`~django.test.SimpleTestCase.assertRedirects`.

* The ``secure`` argument was added to all the request methods of
  :class:`~django.test.Client`. If ``True``, the request will be made
  through HTTPS.

* Requests made with :meth:`Client.login() <django.test.Client.login>` and
  :meth:`Client.logout() <django.test.Client.logout>` respect defaults defined
  in :class:`~django.test.Client` instantiation and are processed through
  middleware.

* :meth:`~django.test.TransactionTestCase.assertNumQueries` now prints
  out the list of executed queries if the assertion fails.

* The ``WSGIRequest`` instance generated by the test handler is now attached to
  the :attr:`django.test.Response.wsgi_request` attribute.

Validators
^^^^^^^^^^

* :class:`~django.core.validators.URLValidator` now accepts an optional
  ``schemes`` argument which allows customization of the accepted URI schemes
  (instead of the defaults ``http(s)`` and ``ftp(s)``).

Backwards incompatible changes in 1.7
=====================================

.. warning::

    In addition to the changes outlined in this section, be sure to review the
    :doc:`deprecation plan </internals/deprecation>` for any features that
    have been removed. If you haven't updated your code within the
    deprecation timeline for a given feature, its removal may appear as a
    backwards incompatible change.

allow_syncdb/allow_migrate
~~~~~~~~~~~~~~~~~~~~~~~~~~

While Django will still look at ``allow_syncdb`` methods even though they
should be renamed to ``allow_migrate``, there is a subtle difference in which
models get passed to these methods.

For apps with migrations, ``allow_migrate`` will now get passed
:ref:`historical models <historical-models>`, which are special versioned models
without custom attributes, methods or managers. Make sure your ``allow_migrate``
methods are only referring to fields or other items in ``model._meta``.

App-loading changes
~~~~~~~~~~~~~~~~~~~

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.

* ``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".

Standalone scripts
^^^^^^^^^^^^^^^^^^

If you're using Django in a plain Python script — rather than a management
command — and you rely on the :envvar:`DJANGO_SETTINGS_MODULE` environment
variable, you must now explicitly initialize Django at the beginning of your
script with::

    >>> import django
    >>> django.setup()

Otherwise, you will hit ``RuntimeError: App registry isn't ready yet.``

App registry consistency
^^^^^^^^^^^^^^^^^^^^^^^^

It is no longer possible to have multiple installed applications with the same
label. In previous versions of Django, this didn't always work correctly, but
didn't crash outright either.

If you have two apps with the same label, you should create an
:class:`~django.apps.AppConfig` for one of them and override its
:class:`~django.apps.AppConfig.label` there. You should then adjust your code
wherever it references this application or its models with the old label.

It isn't possible to import the same model twice through different paths any
more. As of Django 1.6, this may happen only if you're manually putting a
directory and a subdirectory on :envvar:`PYTHONPATH`. Refer to the section on
the new project layout in the :doc:`1.4 release notes </releases/1.4>` for
migration instructions.

You should make sure that:

* All models are defined in applications that are listed in
  :setting:`INSTALLED_APPS` or have an explicit
  :attr:`~django.db.models.Options.app_label`.

* Models aren't imported as a side-effect of loading their application.
  Specifically, you shouldn't import models in the root module of an
  application nor in the module that define its configuration class.

Django will enforce these requirements as of version 1.9, after a deprecation
period.

Subclassing AppCommand
^^^^^^^^^^^^^^^^^^^^^^

Subclasses of :class:`~django.core.management.AppCommand` must now implement a
:meth:`~django.core.management.AppCommand.handle_app_config` method instead of
``handle_app()``. This method receives an :class:`~django.apps.AppConfig`
instance instead of a models module.

Introspecting applications
^^^^^^^^^^^^^^^^^^^^^^^^^^

Since :setting:`INSTALLED_APPS` now supports application configuration classes
in addition to application modules, you should review code that accesses this
setting directly and use the app registry (:attr:`django.apps.apps`) instead.

The app registry has preserved some features of the old app cache. Even though
the app cache was a private API, obsolete methods and arguments will be
removed through a standard deprecation path, with the exception of the
following changes that take effect immediately:

* ``get_model`` raises :exc:`~exceptions.LookupError` instead of returning
  ``None`` when no model is found.

* The ``only_installed`` argument of ``get_model`` and ``get_models`` no
  longer exists, nor does the ``seed_cache`` argument of ``get_model``.

Management commands and order of :setting:`INSTALLED_APPS`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When several applications provide management commands with the same name,
Django loads the command from the application that comes first in
:setting:`INSTALLED_APPS`. Previous versions loaded the command from the
application that came last.

This brings discovery of management commands in line with other parts of
Django that rely on the order of :setting:`INSTALLED_APPS`, such as static
files, templates, and translations.

Behavior of ``LocMemCache`` regarding pickle errors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An inconsistency existed in previous versions of Django regarding how pickle
errors are handled by different cache backends.
``django.core.cache.backends.locmem.LocMemCache`` used to fail silently when
such an error occurs, which is inconsistent with other backends and leads to
cache-specific errors. This has been fixed in Django 1.7, see
`Ticket #21200`_ for more details.

.. _Ticket #21200: https://code.djangoproject.com/ticket/21200

Cache keys are now generated from the request's absolute URL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Previous versions of Django generated cache keys using a request's path and
query string but not the scheme or host. If a Django application was serving
multiple subdomains or domains, cache keys could collide. In Django 1.7, cache
keys vary by the absolute URL of the request including scheme, host, path, and
query string. For example, the URL portion of a cache key is now generated from
``http://www.example.com/path/to/?key=val`` rather than ``/path/to/?key=val``.
The cache keys generated by Django 1.7 will be different from the keys
generated by older versions of Django. After upgrading to Django 1.7, the first
request to any previously cached URL will be a cache miss .

Passing ``None`` to ``Manager.db_manager()``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In previous versions of Django, it was possible to use
``db_manager(using=None)`` on a model manager instance to obtain a manager
instance using default routing behavior, overriding any manually specified
database routing. In Django 1.7, a value of ``None`` passed to db_manager will
produce a router that *retains* any manually assigned database routing -- the
manager will *not* be reset. This was necessary to resolve an inconsistency in
the way routing information cascaded over joins. See `Ticket #13724`_ for more
details.

.. _Ticket #13724: https://code.djangoproject.com/ticket/13724

pytz may be required
~~~~~~~~~~~~~~~~~~~~

If your project handles datetimes before 1970 or after 2037 and Django raises
a :exc:`~exceptions.ValueError` when encountering them, you will have to
install pytz_. You may be affected by this problem if you use Django's time
zone-related date formats or :mod:`django.contrib.syndication`.

``remove()`` and ``clear()`` methods of related managers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The ``remove()`` and ``clear()`` methods of the related managers created by
``ForeignKey``, ``GenericForeignKey``, and ``ManyToManyField`` suffered from a
number of issues. Some operations ran multiple data modifying queries without
wrapping them in a transaction, and some operations didn't respect default
filtering when it was present (i.e. when the default manager on the related
model implemented a custom ``get_queryset()``).

Fixing the issues introduced some backward incompatible changes:

- The default implementation of ``remove()`` for ``ForeignKey`` related managers
  changed from a series of ``Model.save()`` calls to a single
  ``QuerySet.update()`` call. The change means that ``pre_save`` and
  ``post_save`` signals aren't sent anymore. You can use the ``bulk=False``
  keyword argument to revert to the previous behavior.

- The ``remove()`` and ``clear()`` methods for ``GenericForeignKey`` related
  managers now perform bulk delete. The ``Model.delete()`` method isn't called
  on each instance anymore. You can use the ``bulk=False`` keyword argument to
  revert to the previous behavior.

- The ``remove()`` and ``clear()`` methods for ``ManyToManyField`` related
  managers perform nested queries when filtering is involved, which may or
  may not be an issue depending on your database and your data itself.
  See :ref:`this note <nested-queries-performance>` for more details.

.. _pytz: https://pypi.python.org/pypi/pytz/

Miscellaneous
~~~~~~~~~~~~~

* The :meth:`django.core.files.uploadhandler.FileUploadHandler.new_file()`
  method is now passed an additional ``content_type_extra`` parameter. If you
  have a custom :class:`~django.core.files.uploadhandler.FileUploadHandler`
  that implements ``new_file()``, be sure it accepts this new parameter.

* :class:`ModelFormSet<django.forms.models.BaseModelFormSet>`’s no longer
  delete instances when ``save(commit=False)`` is called. See
  :attr:`~django.forms.formsets.BaseFormSet.can_delete` for instructions on how
  to manually delete objects from deleted forms.

* Loading empty fixtures emits a ``RuntimeWarning`` rather than raising
  :class:`~django.core.management.CommandError`.

* :func:`django.contrib.staticfiles.views.serve` will now raise an
  :exc:`~django.http.Http404` exception instead of
  :exc:`~django.core.exceptions.ImproperlyConfigured` when :setting:`DEBUG`
  is ``False``. This change removes the need to conditionally add the view to
  your root URLconf, which in turn makes it safe to reverse by name. It also
  removes the ability for visitors to generate spurious HTTP 500 errors by
  requesting static files that don't exist or haven't been collected yet.

* The :meth:`django.db.models.Model.__eq__` method is now defined in a
  way where instances of a proxy model and its base model are considered
  equal when primary keys match. Previously only instances of exact same
  class were considered equal on primary key match.

* The :meth:`django.db.models.Model.__eq__` method has changed such that
  two ``Model`` instances without primary key values won't be considered
  equal (unless they are the same instance).

* The :meth:`django.db.models.Model.__hash__` will now raise ``TypeError``
  when called on an instance without a primary key value. This is done to
  avoid mutable ``__hash__`` values in containers.

* :class:`~django.db.models.AutoField` columns in SQLite databases will now be
  created using the ``AUTOINCREMENT`` option, which guarantees monotonic
  increments. This will cause primary key numbering behavior to change on
  SQLite, becoming consistent with most other SQL databases. This will only
  apply to newly created tables. If you have a database created with an older
  version of Django, you will need to migrate it to take advantage of this
  feature. For example, you could do the following:

  #) Use :djadmin:`dumpdata` to save your data.
  #) Rename the existing database file (keep it as a backup).
  #) Run :djadmin:`migrate` to create the updated schema.
  #) Use :djadmin:`loaddata` to import the fixtures you exported in (1).

* ``django.contrib.auth.models.AbstractUser`` no longer defines a
  :meth:`~django.db.models.Model.get_absolute_url()` method. The old definition
  returned  ``"/users/%s/" % urlquote(self.username)`` which was arbitrary
  since applications may or may not define such a url in ``urlpatterns``.
  Define a ``get_absolute_url()`` method on your own custom user object or use
  :setting:`ABSOLUTE_URL_OVERRIDES` if you want a URL for your user.

* The static asset-serving functionality of the
  :class:`django.test.LiveServerTestCase` class has been simplified: Now it's
  only able to serve content already present in :setting:`STATIC_ROOT` when
  tests are run. The ability to transparently serve all the static assets
  (similarly to what one gets with :setting:`DEBUG = True <DEBUG>` at
  development-time) has been moved to a new class that lives in the
  ``staticfiles`` application (the one actually in charge of such feature):
  :class:`django.contrib.staticfiles.testing.StaticLiveServerCase`. In other
  words, ``LiveServerTestCase`` itself is less powerful but at the same time
  has less magic.

  Rationale behind this is removal of dependency of non-contrib code on
  contrib applications.

* The old cache URI syntax (e.g. ``"locmem://"``) is no longer supported. It
  still worked, even though it was not documented or officially supported. If
  you're still using it, please update to the current :setting:`CACHES` syntax.

* The default ordering of ``Form`` fields in case of inheritance has changed to
  follow normal Python MRO. Fields are now discovered by iterating through the
  MRO in reverse with the topmost class coming last. This only affects you if
  you relied on the default field ordering while having fields defined on both
  the current class *and* on a parent ``Form``.

* The ``required`` argument of
  :class:`~django.forms.extras.widgets.SelectDateWidget` has been removed.
  This widget now respects the form field's ``is_required`` attribute like
  other widgets.

* :meth:`~django.db.models.query.QuerySet.select_related` now chains in the
  same way as other similar calls like ``prefetch_related``. That is,
  ``select_related('foo', 'bar')`` is equivalent to
  ``select_related('foo').select_related('bar')``. Previously the latter would
  have been equivalent to ``select_related('bar')``.

* GeoDjango dropped support for GEOS < 3.1.

* The ``init_connection_state`` method of database backends now executes in
  autocommit mode (unless you set :setting:`AUTOCOMMIT <DATABASE-AUTOCOMMIT>`
  to ``False``). If you maintain a custom database backend, you should check
  that method.

Features deprecated in 1.7
==========================

``django.core.cache.get_cache``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

:func:`django.core.cache.get_cache` has been supplanted by
:data:`django.core.cache.caches`.

``django.utils.dictconfig``/``django.utils.importlib``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``django.utils.dictconfig`` and ``django.utils.importlib`` were copies of
respectively :mod:`logging.config` and :mod:`importlib` provided for Python
versions prior to 2.7. They have been deprecated.

``django.utils.tzinfo``
~~~~~~~~~~~~~~~~~~~~~~~

``django.utils.tzinfo`` provided two :class:`~datetime.tzinfo` subclasses,
``LocalTimezone`` and ``FixedOffset``. They've been deprecated in favor of
more correct alternatives provided by :mod:`django.utils.timezone`,
:func:`django.utils.timezone.get_default_timezone` and
:func:`django.utils.timezone.get_fixed_timezone`.

``django.utils.unittest``
~~~~~~~~~~~~~~~~~~~~~~~~~

``django.utils.unittest`` provided uniform access to the ``unittest2`` library
on all Python versions. Since ``unittest2`` became the standard library's
:mod:`unittest` module in Python 2.7, and Django 1.7 drops support for older
Python versions, this module isn't useful anymore. It has been deprecated. Use
:mod:`unittest` instead.

``django.utils.datastructures.SortedDict``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As :class:`~collections.OrderedDict` was added to the standard library in
Python 2.7, :class:`~django.utils.datastructures.SortedDict` is no longer
needed and has been deprecated.

Custom SQL location for models package
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Previously, if models were organized in a package (``myapp/models/``) rather
than simply ``myapp/models.py``, Django would look for :ref:`initial SQL data
<initial-sql>` in ``myapp/models/sql/``. This bug has been fixed so that Django
will search ``myapp/sql/`` as documented. The old location will continue to
work until Django 1.9.

``declared_fieldsets`` attribute on ``ModelAdmin``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``ModelAdmin.declared_fieldsets`` has been deprecated. Despite being a private
API, it will go through a regular deprecation path. This attribute was mostly
used by methods that bypassed ``ModelAdmin.get_fieldsets()`` but this was
considered a bug and has been addressed.

``syncdb``
~~~~~~~~~~

The ``syncdb`` command has been deprecated in favour of the new ``migrate``
command. ``migrate`` takes the same arguments as ``syncdb`` used to plus a few
more, so it's safe to just change the name you're calling and nothing else.

``util`` modules renamed to ``utils``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following instances of ``util.py`` in the Django codebase have been renamed
to ``utils.py`` in an effort to unify all util and utils references:

* ``django.contrib.admin.util``
* ``django.contrib.gis.db.backends.util``
* ``django.db.backends.util``
* ``django.forms.util``

``get_formsets`` method on ``ModelAdmin``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``ModelAdmin.get_formsets`` has been deprecated in favor of the new
:meth:`~django.contrib.admin.ModelAdmin.get_formsets_with_inlines`, in order to
better handle the case of selecting showing inlines on a ``ModelAdmin``.

``IPAddressField``
~~~~~~~~~~~~~~~~~~

The :class:`django.db.models.IPAddressField` and
:class:`django.forms.IPAddressField` fields have been deprecated in favor of
:class:`django.db.models.GenericIPAddressField` and
:class:`django.forms.GenericIPAddressField`.

``BaseMemcachedCache._get_memcache_timeout`` method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The ``BaseMemcachedCache._get_memcache_timeout()`` method has been renamed to
``get_backend_timeout()``. Despite being a private API, it will go through the
normal deprecation.

Natural key serialization options
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The ``--natural`` and ``-n`` options for :djadmin:`dumpdata` have been
deprecated. Use :djadminopt:`--natural-foreign` instead.

Similarly, the ``use_natural_keys`` argument for ``serializers.serialize()``
has been deprecated. Use ``use_natural_foreign_keys`` instead.

Merging of ``POST`` and ``GET`` arguments into ``WSGIRequest.REQUEST``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It was already strongly suggested that you use ``GET`` and ``POST`` instead of
``REQUEST``, because the former are more explicit. The property ``REQUEST`` is
deprecated and will be removed in Django 1.9.

``django.utils.datastructures.MergeDict`` class
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``MergeDict`` exists primarily to support merging ``POST`` and ``GET``
arguments into a ``REQUEST`` property on ``WSGIRequest``. To merge
dictionaries, use ``dict.update()`` instead. The class ``MergeDict`` is
deprecated and will be removed in Django 1.9.

Language codes ``zh-cn``, ``zh-tw`` and ``fy-nl``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The currently used language codes for Simplified Chinese ``zh-cn``,
Traditional Chinese ``zh-tw`` and (Western) Frysian ``fy-nl`` are deprecated
and should be replaced by the language codes ``zh-hans``, ``zh-hant`` and
``fy`` respectively. If you use these language codes, you should rename the
locale directories and update your settings to reflect these changes. The
deprecated language codes will be removed in Django 1.9.

``django.utils.functional.memoize`` function
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The function ``memoize`` is deprecated and should be replaced by the
``functools.lru_cache`` decorator (available from Python 3.2 onwards).

Django ships a backport of this decorator for older Python versions and it's
available at ``django.utils.lru_cache.lru_cache``. The deprecated function will
be removed in Django 1.9.

Geo Sitemaps
~~~~~~~~~~~~

Google has retired support for the Geo Sitemaps format. Hence Django support
for Geo Sitemaps is deprecated and will be removed in Django 1.8.

Passing callable arguments to queryset methods
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Callable arguments for querysets were an undocumented feature that was
unreliable. It's been deprecated and will be removed in Django 1.9.

Callable arguments were evaluated when a queryset was constructed rather than
when it was evaluated, thus this feature didn't offer any benefit compared to
evaluating arguments before passing them to queryset and created confusion that
the arguments may have been evaluated at query time.

``ADMIN_FOR`` setting
~~~~~~~~~~~~~~~~~~~~~

The ``ADMIN_FOR`` feature, part of the admindocs, has been removed. You can
remove the setting from your configuration at your convenience.

``SplitDateTimeWidget`` with ``DateTimeField``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``SplitDateTimeWidget`` support in :class:`~django.forms.DateTimeField` is
deprecated, use ``SplitDateTimeWidget`` with
:class:`~django.forms.SplitDateTimeField` instead.