1.2.txt

.. _releases-1.2:

============================================
Django 1.2 release notes — UNDER DEVELOPMENT
============================================

This page documents release notes for the as-yet-unreleased Django 1.2. As such,
it's tentative and subject to change. It provides up-to-date information for
those who are following trunk.

Django 1.2 includes a number of nifty `new features`_, lots of bug
fixes and an easy upgrade path from Django 1.1.

.. _new features: `What's new in Django 1.2`_

.. _backwards-incompatible-changes-1.2:

Backwards-incompatible changes in 1.2
=====================================

CSRF Protection
---------------

We've made large changes to the way CSRF protection works, detailed in
:ref:`the CSRF documentaton <ref-contrib-csrf>`. Here are the major changes you
should be aware of:

 * ``CsrfResponseMiddleware`` and ``CsrfMiddleware`` have been deprecated and
   will be removed completely in Django 1.4, in favor of a template tag that
   should be inserted into forms.

 * All contrib apps use a ``csrf_protect`` decorator to protect the view. This
   requires the use of the csrf_token template tag in the template. If you
   have used custom templates for contrib views, you MUST READ THE :ref:`UPGRADE
   INSTRUCTIONS <ref-csrf-upgrading-notes>` to fix those templates.

 * ``CsrfViewMiddleware`` is included in :setting:`MIDDLEWARE_CLASSES` by
   default. This turns on CSRF protection by default, so views that accept
   POST requests need to be written to work with the middleware. Instructions
   on how to do this are found in the CSRF docs.

 * All of the CSRF has moved from contrib to core (with backwards compatible
   imports in the old locations, which are deprecated).

:ttag:`if` tag changes
----------------------

Due to new features in the :ttag:`if` template tag, it no longer accepts 'and',
'or' and 'not' as valid **variable** names. Previously, that worked in some
cases even though these strings were normally treated as keywords. Now, the
keyword status is always enforced, and template code such as ``{% if not %}`` or
``{% if and %}`` will throw a ``TemplateSyntaxError``. Also, ``in`` is a new
keyword and so is not a valid variable name in this context.

``LazyObject``
--------------

``LazyObject`` is an undocumented utility class used for lazily wrapping other
objects of unknown type. In Django 1.1 and earlier, it handled introspection in
a non-standard way, depending on wrapped objects implementing a public method
``get_all_members()``. Since this could easily lead to name clashes, it has been
changed to use the standard method, involving ``__members__`` and ``__dir__()``.
If you used ``LazyObject`` in your own code and implemented the
``get_all_members()`` method for wrapped objects, you need to make the following
changes:

 * If your class does not have special requirements for introspection (i.e., you
   have not implemented ``__getattr__()`` or other methods that allow for
   attributes not discoverable by normal mechanisms), you can simply remove the
   ``get_all_members()`` method. The default implementation on ``LazyObject``
   will do the right thing.

 * If you have more complex requirements for introspection, first rename the
   ``get_all_members()`` method to ``__dir__()``. This is the standard method,
   from Python 2.6 onwards, for supporting introspection. If you require
   support for Python < 2.6, add the following code to the class::

       __members__ = property(lambda self: self.__dir__())

Specifying databases
--------------------

Prior to Django 1.1, Django used a number of settings to control access to a
single database. Django 1.2 introduces support for multiple databases, and as
a result, the way you define database settings has changed.

Any existing Django settings file will continue to work as expected until
Django 1.4. Until then, old-style database settings will be automatically
translated to the new-style format.

In the old-style (pre 1.2) format, you had a number of ``DATABASE_`` settings
in your settings file. For example::

    DATABASE_NAME = 'test_db'
    DATABASE_ENGINE = 'postgresql_psycopg2'
    DATABASE_USER = 'myusername'
    DATABASE_PASSWORD = 's3krit'

These settings are now in a dictionary named :setting:`DATABASES`. Each item in
the dictionary corresponds to a single database connection, with the name
``'default'`` describing the default database connection. The setting names
have also been shortened. The previous sample settings would now look like this::

    DATABASES = {
        'default': {
            'NAME': 'test_db',
            'ENGINE': 'django.db.backends.postgresql_psycopg2',
            'USER': 'myusername',
            'PASSWORD': 's3krit',
        }
    }

This affects the following settings:

    =========================================  ==========================
     Old setting                                New Setting
    =========================================  ==========================
    :setting:`DATABASE_ENGINE`                 :setting:`ENGINE`
    :setting:`DATABASE_HOST`                   :setting:`HOST`
    :setting:`DATABASE_NAME`                   :setting:`NAME`
    :setting:`DATABASE_OPTIONS`                :setting:`OPTIONS`
    :setting:`DATABASE_PASSWORD`               :setting:`PASSWORD`
    :setting:`DATABASE_PORT`                   :setting:`PORT`
    :setting:`DATABASE_USER`                   :setting:`USER`
    :setting:`TEST_DATABASE_CHARSET`           :setting:`TEST_CHARSET`
    :setting:`TEST_DATABASE_COLLATION`         :setting:`TEST_COLLATION`
    :setting:`TEST_DATABASE_NAME`              :setting:`TEST_NAME`
    =========================================  ==========================

These changes are also required if you have manually created a database
connection using ``DatabaseWrapper()`` from your database backend of choice.

In addition to the change in structure, Django 1.2 removes the special
handling for the built-in database backends. All database backends
must now be specified by a fully qualified module name (i.e.,
``django.db.backends.postgresql_psycopg2``, rather than just
``postgresql_psycopg2``).

``__dict__`` on model instances
-------------------------------

Historically, the ``__dict__`` attribute of a model instance has only contained
attributes corresponding to the fields on a model.

In order to support multiple database configurations, Django 1.2 has
added a ``_state`` attribute to object instances. This attribute will
appear in ``__dict__`` for a model instance. If your code relies on
iterating over __dict__ to obtain a list of fields, you must now
filter the ``_state`` attribute out of ``__dict__``.

``get_db_prep_*()`` methods on ``Field``
----------------------------------------

Prior to 1.2, a custom ``Field`` had the option of defining several
functions to support conversion of Python values into
database-compatible values. A custom field might look something like::

    class CustomModelField(models.Field):
        # ...

        def get_db_prep_save(self, value):
            # ...

        def get_db_prep_value(self, value):
            # ...

        def get_db_prep_lookup(self, lookup_type, value):
            # ...

In 1.2, these three methods have undergone a change in prototype, and
two extra methods have been introduced::

    class CustomModelField(models.Field):
        # ...

        def get_prep_value(self, value):
            # ...

        def get_prep_lookup(self, lookup_type, value):
            # ...

        def get_db_prep_save(self, value, connection):
            # ...

        def get_db_prep_value(self, value, connection, prepared=False):
            # ...

        def get_db_prep_lookup(self, lookup_type, value, connection, prepared=False):
            # ...

These changes are required to support multiple databases --
``get_db_prep_*`` can no longer make any assumptions regarding the
database for which it is preparing. The ``connection`` argument now
provides the preparation methods with the specific connection for
which the value is being prepared.

The two new methods exist to differentiate general data-preparation
requirements from requirements that are database-specific. The
``prepared`` argument is used to indicate to the database-preparation
methods whether generic value preparation has been performed. If
an unprepared (i.e., ``prepared=False``) value is provided to the
``get_db_prep_*()`` calls, they should invoke the corresponding
``get_prep_*()`` calls to perform generic data preparation.

We've provided conversion functions that will transparently
convert functions adhering to the old prototype into functions
compatible with the new prototype. However, these conversion functions
will be removed in Django 1.4, so you should upgrade your ``Field``
definitions to use the new prototype now, just to get it over with.

If your ``get_db_prep_*()`` methods made no use of the database
connection, you should be able to upgrade by renaming
``get_db_prep_value()`` to ``get_prep_value()`` and
``get_db_prep_lookup()`` to ``get_prep_lookup()`. If you require
database specific conversions, then you will need to provide an
implementation ``get_db_prep_*`` that uses the ``connection``
argument to resolve database-specific values.

Stateful template tags
----------------------

Template tags that store rendering state on the node itself may experience
problems if they are used with the new :ref:`cached
template loader<template-loaders>`.

All of the built-in Django template tags are safe to use with the cached
loader, but if you're using custom template tags that come from third
party packages, or from your own code, you should ensure that the
``Node`` implementation for each tag is thread-safe. For more
information, see
:ref:`template tag thread safety considerations<template_tag_thread_safety>`.

You may also need to update your templates if you were relying on the
implementation of Django's template tags *not* being thread safe. The
:ttag:`cycle` tag is the most likely to be affected in this way,
especially when used in conjunction with the :ttag:`include` tag.
Consider the following template fragment::

    {% for object in object_list %}
        {% include "subtemplate.html" %}
    {% endfor %}

with a ``subtemplate.html`` that reads::

    {% cycle 'even' 'odd' %}

Using the non thread-safe, pre-Django 1.2 renderer, this would output::

    even odd even odd ...

Using the thread-safe Django 1.2 renderer, you will instead get::

    even even even even ...

This is because the each rendering of the :ttag:`include` tag is an
independent rendering. When the :ttag:`cycle` tag was not thread safe,
the state of the :ttag:`cycle` tag would leak between multiple renderings
of the same :ttag:`include`. Now that the :ttag:`cycle` tag is thread safe,
this leakage no longer occurs.

Test runner exit status code
----------------------------

The exit status code of the test runners (``tests/runtests.py`` and ``python
manage.py test``) no longer represents the number of failed tests, because a
failure of 256 or more tests resulted in a wrong exit status code. The exit
status code for the test runner is now 0 for success (no failing tests) and 1
for any number of test failures. If needed, the number of test failures can be
found at the end of the test runner's output.

Cookie encoding
---------------

To fix bugs with cookies in Internet Explorer, Safari, and possibly other
browsers, our encoding of cookie values was changed so that the characters
comma and semi-colon are treated as non-safe characters, and are therefore
encoded as ``\054`` and ``\073`` respectively.  This could produce backwards
incompatibilities, especially if you are storing comma or semi-colon in
cookies and have javascript code that parses and manipulates cookie values
client-side.

``user_passes_test``, ``login_required`` and ``permission_required``
--------------------------------------------------------------------

``django.contrib.auth.decorators`` provides the decorators ``login_required``,
``permission_required`` and ``user_passes_test``. Previously it was possible to
use these decorators both on functions (where the first argument is 'request')
and on methods (where the first argument is 'self', and the second argument is
'request'). However, we have found that the trick which enabled this is
flawed. It only works in limited circumstances, and produces errors that are
very difficult to debug when it does not work.

For this reason, the 'auto adapt' behaviour has been removed, and if you are
using these decorators on methods, you will need to manually apply
:func:`django.utils.decorators.method_decorator` to convert the decorator to one
that works with methods. You would change code from this::

    class MyClass(object):

        @login_required
        def my_view(self, request):
            pass

to this::

    from django.utils.decorators import method_decorator

    class MyClass(object):

        @method_decorator(login_required)
        def my_view(self, request):
            pass

or::

    from django.utils.decorators import method_decorator

    login_required_m = method_decorator(login_required)

    class MyClass(object):

        @login_required_m
        def my_view(self, request):
            pass

For those following trunk, this change also applies to other decorators
introduced since 1.1, including ``csrf_protect``, ``cache_control`` and anything
created using ``decorator_from_middleware``.

``ModelForm.is_valid()`` and ``ModelForm.errors``
-------------------------------------------------

Much of the validation work for ModelForms has been moved down to the model
level. As a result, the first time you call ``ModelForm.is_valid()``, access
``ModelForm.errors`` or otherwise trigger form validation, your model will be
cleaned in-place. This conversion used to happen when the model was saved. If
you need an unmodified instance of your model, you should pass a copy to the
``ModelForm`` constructor.


.. _deprecated-features-1.2:

``BooleanField`` on MySQL
--------------------------

In previous versions of Django ``BoleanFields`` under MySQL would return their
values as either ``1`` or ``0``, instead of ``True`` or ``False``.  For most
people this shouldn't have been a problem because ``bool`` is a subclass of
``int``, however in Django 1.2 MySQL correctly returns a real ``bool``.  The
only time this should ever be an issue is if you were expecting printing the
``repr`` of a ``BooleanField`` to print ``1`` or ``0``.

Features deprecated in 1.2
==========================

``postgresql`` database backend
-------------------------------

The ``psycopg1`` library has not been updated since October 2005. As a
result, the ``postgresql`` database backend, which depends on this
library, has been deprecated.

If you are currently using the ``postgresql`` backend, you should
migrate to using the ``postgresql_psycopg2`` backend. To update your
code, install the ``psycopg2`` library and change the
``DATABASE_ENGINE`` setting to read ``postgresql_psycopg2``.

CSRF response-rewriting middleware
----------------------------------

``CsrfResponseMiddleware``, the middleware that automatically inserted CSRF
tokens into POST forms in outgoing pages, has been deprecated in favor of a
template tag method (see above), and will be removed completely in Django
1.4. ``CsrfMiddleware``, which includes the functionality of
``CsrfResponseMiddleware`` and ``CsrfViewMiddleware``, has likewise been
deprecated.

Also, the CSRF module has moved from contrib to core, and the old imports are
deprecated, as described in the :ref:`upgrading notes <ref-csrf-upgrading-notes>`.

``SMTPConnection``
------------------

The ``SMTPConnection`` class has been deprecated in favor of a generic
e-mail backend API. Old code that explicitly instantiated an instance
of an SMTPConnection::

    from django.core.mail import SMTPConnection
    connection = SMTPConnection()
    messages = get_notification_email()
    connection.send_messages(messages)

...should now call :meth:`~django.core.mail.get_connection()` to
instantiate a generic e-mail connection::

    from django.core.mail import get_connection
    connection = get_connection()
    messages = get_notification_email()
    connection.send_messages(messages)

Depending on the value of the :setting:`EMAIL_BACKEND` setting, this
may not return an SMTP connection. If you explicitly require an SMTP
connection with which to send e-mail, you can explicitly request an
SMTP connection::

    from django.core.mail import get_connection
    connection = get_connection('django.core.mail.backends.smtp.EmailBackend')
    messages = get_notification_email()
    connection.send_messages(messages)

If your call to construct an instance of ``SMTPConnection`` required
additional arguments, those arguments can be passed to the
:meth:`~django.core.mail.get_connection()` call::

    connection = get_connection('django.core.mail.backends.smtp.EmailBackend', hostname='localhost', port=1234)

User Messages API
-----------------

The API for storing messages in the user ``Message`` model (via
``user.message_set.create``) is now deprecated and will be removed in Django
1.4 according to the standard :ref:`release process <internals-release-process>`.

To upgrade your code, you need to replace any instances of this::

    user.message_set.create('a message')

...with the following::

    from django.contrib import messages
    messages.add_message(request, messages.INFO, 'a message')

Additionally, if you make use of the method, you need to replace the
following::

    for message in user.get_and_delete_messages():
        ...

...with::

    from django.contrib import messages
    for message in messages.get_messages(request):
        ...

For more information, see the full
:ref:`messages documentation <ref-contrib-messages>`. You should begin to
update your code to use the new API immediately.

Date format helper functions
----------------------------

``django.utils.translation.get_date_formats()`` and
``django.utils.translation.get_partial_date_formats()`` have been deprecated
in favor of the appropriate calls to ``django.utils.formats.get_format()``,
which is locale-aware when :setting:`USE_L10N` is set to ``True``, and falls
back to default settings if set to ``False``.

To get the different date formats, instead of writing this::

    from django.utils.translation import get_date_formats
    date_format, datetime_format, time_format = get_date_formats()

...use::

    from django.utils import formats
    date_format = formats.get_format('DATE_FORMAT')
    datetime_format = formats.get_format('DATETIME_FORMAT')
    time_format = formats.get_format('TIME_FORMAT')

Or, when directly formatting a date value::

    from django.utils import formats
    value_formatted = formats.date_format(value, 'DATETIME_FORMAT')

The same applies to the globals found in ``django.forms.fields``:

  * ``DEFAULT_DATE_INPUT_FORMATS``
  * ``DEFAULT_TIME_INPUT_FORMATS``
  * ``DEFAULT_DATETIME_INPUT_FORMATS``

Use ``django.utils.formats.get_format()`` to get the appropriate formats.

email_re
--------

An undocumented regex for validating email addresses has been moved from
django.form.fields to django.core.validators. You will need to update
your imports if you are using it.

Function-based test runners
---------------------------

Django 1.2 changes the test runner tools to use a class-based
approach. Old style function-based test runners will still work, but
should be updated to use the new :ref:`class-based runners
<topics-testing-test_runner>`.

.. _1.2-updating-feeds:

``Feed`` in ``django.contrib.syndication.feeds``
------------------------------------------------

The :class:`django.contrib.syndication.feeds.Feed` class has been
replaced by the :class:`django.contrib.syndication.views.Feed` class.
The old ``feeds.Feed`` class is deprecated, and will be removed in
Django 1.4.

The new class has an almost identical API, but allows instances to be
used as views. For example, consider the use of the old framework in
the following :ref:`URLconf <topics-http-urls>`::

    from django.conf.urls.defaults import *
    from myproject.feeds import LatestEntries, LatestEntriesByCategory

    feeds = {
        'latest': LatestEntries,
        'categories': LatestEntriesByCategory,
    }

    urlpatterns = patterns('',
        # ...
        (r'^feeds/(?P<url>.*)/$', 'django.contrib.syndication.views.feed',
            {'feed_dict': feeds}),
        # ...
    )

Using the new Feed class, these feeds can be deployed directly as views::

    from django.conf.urls.defaults import *
    from myproject.feeds import LatestEntries, LatestEntriesByCategory

    urlpatterns = patterns('',
        # ...
        (r'^feeds/latest/$', LatestEntries()),
        (r'^feeds/categories/(?P<category_id>\d+)/$', LatestEntriesByCategory()),
        # ...
    )

If you currently use the ``feed()`` view, the ``LatestEntries`` class would
often not need to be modified apart from subclassing the new
:class:`~django.contrib.syndication.views.Feed` class. The exception is if
Django was automatically working out the name of the template to use to render
the feed's description and title elements (if you were not specifying the
``title_template`` and ``description_template`` attributes). You should ensure
that you always specify ``title_template`` and ``description_template``
attributes, or provide ``item_title()`` and ``item_description()`` methods.

However, ``LatestEntriesByCategory`` uses the ``get_object()`` method
with the ``bits`` argument to specify a specific category to show. In
the new :class:`~django.contrib.syndication.views.Feed` class,
``get_object()`` method takes a ``request`` and arguments from the
URL, so it would look like this::

    from django.contrib.syndication.views import Feed
    from django.shortcuts import get_object_or_404
    from myproject.models import Category

    class LatestEntriesByCategory(Feed):
        def get_object(self, request, category_id):
            return get_object_or_404(Category, id=category_id)

        # ...

Additionally, the ``get_feed()`` method on ``Feed`` classes now take
different arguments, which may impact you if you use the ``Feed``
classes directly. Instead of just taking an optional ``url`` argument,
it now takes two arguments: the object returned by its own
``get_object()`` method, and the current ``request`` object.

To take into account ``Feed`` classes not being initialized for each
request, the ``__init__()`` method now takes no arguments by default.
Previously it would have taken the ``slug`` from the URL and the
``request`` object.

In accordance with `RSS best practices`_, RSS feeds will now include
an ``atom:link`` element. You may need to update your tests to take
this into account.

For more information, see the full :ref:`syndication framework
documentation <ref-contrib-syndication>`.

.. _RSS best practices: http://www.rssboard.org/rss-profile

Technical message IDs
---------------------

Up to version 1.1 Django used :ref:`technical message IDs<technical-messages>`
to provide localizers the possibility to translate date and time formats. They
were translatable :term:`translation strings <translation string>` that could
be recognized because they were all upper case (for example
``DATETIME_FORMAT``, ``DATE_FORMAT``, ``TIME_FORMAT``). They have been
deprecated in favor of the new :ref:`Format localization
<format-localization>` infrastructure that allows localizers to specify that
information in a ``formats.py`` file in the corresponding
``django/conf/locale/<locale name>/`` directory.

What's new in Django 1.2
========================

CSRF support
------------

Django now has much improved protection against :ref:`Cross-Site
Request Forgery (CSRF) attacks<ref-contrib-csrf>`. This type of attack
occurs when a malicious Web site contains a link, a form button or
some JavaScript that is intended to perform some action on your Web
site, using the credentials of a logged-in user who visits the
malicious site in their browser. A related type of attack, "login
CSRF," where an attacking site tricks a user's browser into logging
into a site with someone else's credentials, is also covered.

E-mail backends
---------------

You can now :ref:`configure the way that Django sends e-mail
<topic-email-backends>`. Instead of using SMTP to send all e-mail, you
can now choose a configurable e-mail backend to send messages. If your
hosting provider uses a sandbox or some other non-SMTP technique for
sending mail, you can now construct an e-mail backend that will allow
Django's standard :ref:`mail sending methods<topics-email>` to use
those facilities.

This also makes it easier to debug mail sending. Django ships with
backend implementations that allow you to send e-mail to a
:ref:`file<topic-email-file-backend>`, to the
:ref:`console<topic-email-console-backend>`, or to
:ref:`memory<topic-email-memory-backend>`. You can even configure all
e-mail to be :ref:`thrown away<topic-email-dummy-backend>`.

Messages framework
------------------

Django now includes a robust and configurable :ref:`messages framework
<ref-contrib-messages>` with built-in support for cookie- and session-based
messaging, for both anonymous and authenticated clients. The messages framework
replaces the deprecated user message API and allows you to temporarily store
messages in one request and retrieve them for display in a subsequent request
(usually the next one).

Support for multiple databases
------------------------------

Django 1.2 adds the ability to use :ref:`more than one database
<topics-db-multi-db>` in your Django project. Queries can be
issued at a specific database with the `using()` method on
``QuerySet`` objects. Individual objects can be saved to a specific database
by providing a ``using`` argument when you call ``save()``.

'Smart' if tag
--------------

The :ttag:`if` tag has been upgraded to be much more powerful. First, we've
added support for comparison operators. No longer will you have to type:

.. code-block:: html+django

    {% ifnotequal a b %}
     ...
    {% endifnotequal %}

You can now do this:

.. code-block:: html+django

    {% if a != b %}
     ...
    {% endif %}

There's really no reason to use ``{% ifequal %}`` or ``{% ifnotequal %}``
anymore, unless you're the nostalgic type.

The operators supported are ``==``, ``!=``, ``<``, ``>``, ``<=``, ``>=``,
``in`` and ``not in``, all of which work like the Python operators, in addition
to ``and``, ``or`` and ``not``, which were already supported.

Also, filters may now be used in the ``if`` expression. For example:

.. code-block:: html+django

      <div
        {% if user.email|lower == message.recipient|lower %}
          class="highlight"
        {% endif %}
      >{{ message }}</div>

Template caching
----------------

In previous versions of Django, every time you rendered a template, it
would be reloaded from disk. In Django 1.2, you can use a :ref:`cached
template loader <template-loaders>` to load templates once, then
cache the result for every subsequent render. This can lead to a
significant performance improvement if your templates are broken into
lots of smaller subtemplates (using the ``{% extends %}`` or ``{%
include %}`` tags).

As a side effect, it is now much easier to support non-Django template
languages. For more details, see the :ref:`notes on supporting
non-Django template languages<topic-template-alternate-language>`.

Natural keys in fixtures
------------------------

Fixtures can now refer to remote objects using
:ref:`topics-serialization-natural-keys`. This lookup scheme is an
alternative to the normal primary-key based object references in a
fixture, improving readability and resolving problems referring to
objects whose primary key value may not be predictable or known.

``BigIntegerField``
-------------------

Models can now use a 64-bit :class:`~django.db.models.BigIntegerField` type.

Fast failure for tests
----------------------

Both the :djadmin:`test` subcommand of ``django-admin.py`` and the ``runtests.py``
script used to run Django's own test suite now support a ``--failfast`` option.
When specified, this option causes the test runner to exit after encountering
a failure instead of continuing with the test run. In addition, the handling
of ``Ctrl-C`` during a test run has been improved to trigger a graceful exit
from the test run that reports details of the tests that were run before the
interruption.

Improved localization
---------------------

Django's :ref:`internationalization framework <topics-i18n>` has been
expanded with locale-aware formatting and form processing. That means, if
enabled, dates and numbers on templates will be displayed using the format
specified for the current locale. Django will also use localized formats
when parsing data in forms. See
:ref:`Format localization <format-localization>` for more details.

``readonly_fields`` in ``ModelAdmin``
-------------------------------------

:attr:`django.contrib.admin.ModelAdmin.readonly_fields` has been added to
enable non-editable fields in add/change pages for models and inlines. Field
and calculated values can be displayed alongside editable fields.

Customizable syntax highlighting
--------------------------------

You can now use a ``DJANGO_COLORS`` environment variable to modify
or disable the colors used by ``django-admin.py`` to provide
:ref:`syntax highlighting <syntax-coloring>`.

Model validation
----------------

Model instances now have support for :ref:`validating their own data
<validating-objects>`, and both model and form fields now accept
configurable lists of :ref:`validators <ref-validators>` specifying
reusable, encapsulated validation behavior. Note, however, that
validation must still be performed explicitly. Simply invoking a model
instance's ``save()`` method will not perform any validation of the
instance's data.

Object-level permissions
------------------------

A foundation for specifying permissions at the per-object level has been added.
Although there is no implementation of this in core, a custom authentication
backend can provide this implementation and it will be used by
:class:`django.contrib.auth.models.User`. See the :ref:`authentication docs
<topics-auth>` for more information.

Permissions for anonymous users
-------------------------------

If you provide a custom auth backend with ``supports_anonymous_user`` set to
``True``, AnonymousUser will check the backend for permissions, just like
User already did.  This is useful for centralizing permission handling - apps
can always delegate the question of whether something is allowed or not to
the authorization/authentication backend. See the :ref:`authentication
docs <topics-auth>` for more details.

Syndication feeds as views
--------------------------

:ref:`Syndication feeds <ref-contrib-syndication>` can now be used directly as
views in your :ref:`URLconf <topics-http-urls>`. This means that you can
maintain complete control over the URL structure of your feeds. Like any other view, feeds views are passed a ``request`` object, so you can
do anything you would normally do with a view, like user based access control,
or making a feed a named URL.

Relaxed requirements for usernames
----------------------------------

The built-in :class:`~django.contrib.auth.models.User` model's
:attr:`~django.contrib.auth.models.User.username` field now allows a wider range
of characters, including ``@``, ``+``, ``.`` and ``-`` characters.

Deprecation of old language code ``no``
---------------------------------------

The currently used language code for Norwegian Bokmål ``no`` is being
replaced by the more common language code ``nb``, which should be updated
by translators from now on.