django/docs/releases/1.4.txt

============================================
Django 1.4 release notes - UNDER DEVELOPMENT
============================================

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

Django 1.4 includes various `new features`_ and some minor `backwards
incompatible changes`_. There are also some features that have been dropped,
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 1.4`_
.. _backwards incompatible changes: backwards-incompatible-changes-1.4_
.. _begun the deprecation process for some features: deprecated-features-1.4_

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

While not a new feature, it's important to note that Django 1.4 introduces the
second shift in our Python compatibility policy since Django's initial public
debut. Django 1.2 dropped support for Python 2.3; now Django 1.4 drops support
for Python 2.4. As such, the minimum Python version required for Django is now
2.5, and Django is tested and supported on Python 2.5, 2.6 and 2.7.

This change should affect only a small number of Django users, as most
operating-system vendors today are shipping Python 2.5 or newer as their default
version. If you're still using Python 2.4, however, you'll need to stick to
Django 1.3 until you can upgrade; per :doc:`our support policy
</internals/release-process>`, Django 1.3 will continue to receive security
support until the release of Django 1.5.

Django does not support Python 3.x at this time. A document outlining our full
timeline for deprecating Python 2.x and moving to Python 3.x will be published
before the release of Django 1.4.

What's new in Django 1.4
========================

``SELECT FOR UPDATE`` support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.4 now includes a :meth:`QuerySet.select_for_update()
<django.db.models.query.QuerySet.select_for_update>` method which generates a
``SELECT ... FOR UPDATE`` SQL query. This will lock rows until the end of the
transaction, meaning that other transactions cannot modify or delete rows
matched by a ``FOR UPDATE`` query.

For more details, see the documentation for
:meth:`~django.db.models.query.QuerySet.select_for_update`.

HTML5
~~~~~

We've switched the admin and other bundled templates to use the HTML5
doctype. While Django will be careful in its use of HTML5 features, to maintain
compatibility with older browsers, this change means that you can use any HTML5
features you need in admin pages without having to lose HTML validity or
override the provided templates to change the doctype.

Supported browsers for the admin
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django hasn't had a clear policy on which browsers are supported for using the
admin app. Django's new policy formalizes existing practices: `YUI's A-grade`_
browsers should provide a fully-functional admin experience, with the notable
exception of IE6, which is no longer supported.

Released over ten years ago, IE6 imposes many limitations on modern web
development. The practical implications of this policy are that contributors
are free to improve the admin without consideration for these limitations.

This new policy **has no impact** on development outside of the admin. Users of
Django are free to develop webapps compatible with any range of browsers.

.. _YUI's A-grade: http://yuilibrary.com/yui/docs/tutorials/gbs/

List filters in admin interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Prior to Django 1.4, the Django admin app allowed specifying change list
filters by specifying a field lookup (including spanning relations), and
not custom filters. This has been rectified with a simple API previously
known as "FilterSpec" which was used internally. For more details, see the
documentation for :attr:`~django.contrib.admin.ModelAdmin.list_filter`.

Multiple sort in admin interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The admin change list now supports sorting on multiple columns. It respects
all elements of the :attr:`~django.contrib.admin.ModelAdmin.ordering`
attribute, and sorting on multiple columns by clicking on headers is designed
to work similarly to how desktop GUIs do it. The new hook
:meth:`~django.contrib.admin.ModelAdmin.get_ordering` for specifying the
ordering dynamically (e.g. depending on the request) has also been added.

``ModelAdmin.save_related()``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A new :meth:`~django.contrib.admin.ModelAdmin.save_related` hook was added to
:mod:`~django.contrib.admin.ModelAdmin` to ease the customization of how
related objects are saved in the admin.

Tools for cryptographic signing
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.4 adds both a low-level API for signing values and a high-level API
for setting and reading signed cookies, one of the most common uses of
signing in Web applications.

See :doc:`cryptographic signing </topics/signing>` docs for more information.

Cookie-based session backend
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.4 introduces a new cookie based backend for the session framework
which uses the tools for :doc:`cryptographic signing </topics/signing>` to
store the session data in the client's browser.

See the :ref:`cookie-based backend <cookie-session-backend>` docs for
more information.

New form wizard
~~~~~~~~~~~~~~~

The previously shipped ``FormWizard`` of the formtools contrib app has been
replaced with a new implementation that is based on the class based views
introduced in Django 1.3. It features a pluggable storage API and doesn't
require the wizard to pass around hidden fields for every previous step.

Django 1.4 ships with a session based storage backend and a cookie based
storage backend. The latter uses the tools for
:doc:`cryptographic signing </topics/signing>` also introduced in
Django 1.4 to store the wizard state in the user's cookies.

See the :doc:`form wizard </ref/contrib/formtools/form-wizard>` docs for
more information.

Simple clickjacking protection
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We've added a middleware to provide easy protection against `clickjacking
<http://en.wikipedia.org/wiki/Clickjacking>`_ using the X-Frame-Options
header. It's not enabled by default for backwards compatibility reasons, but
you'll almost certainly want to :doc:`enable it </ref/clickjacking/>` to help
plug that security hole for browsers that support the header.

``reverse_lazy``
~~~~~~~~~~~~~~~~

A lazily evaluated version of :func:`django.core.urlresolvers.reverse` was
added to allow using URL reversals before the project's URLConf gets loaded.

Assignment template tags
~~~~~~~~~~~~~~~~~~~~~~~~

A new helper function,
:ref:`assignment_tag<howto-custom-template-tags-assignment-tags>`, was added to
``template.Library`` to ease the creation of template tags that store some
data in a specified context variable.

``truncatechars`` template filter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Added a filter which truncates a string to be no longer than the specified
number of characters. Truncated strings end with a translatable ellipsis
sequence ("..."). See the :tfilter:`truncatechars docs <truncatechars>` for
more details.

Customizable ``SingleObjectMixin`` URLConf kwargs
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Two new attributes,
:attr:`pk_url_kwarg<django.views.generic.detail.SingleObjectMixin.pk_url_kwarg>` and
:attr:`slug_url_kwarg<django.views.generic.detail.SingleObjectMixin.slug_url_kwarg>`,
have been added to :class:`django.views.generic.detail.SingleObjectMixin` to
enable the customization of URLConf keyword arguments used for single
object generic views.

CSRF improvements
~~~~~~~~~~~~~~~~~

We've made various improvements to our CSRF features, including the
:func:`~django.views.decorators.csrf.ensure_csrf_cookie` decorator which can
help with AJAX heavy sites, protection for PUT and DELETE, and settings
:setting:`CSRF_COOKIE_SECURE` and :setting:`CSRF_COOKIE_PATH` which can improve
the security and usefulness of the CSRF protection. See the :doc:`CSRF docs
</ref/contrib/csrf>` for more information.

Error report filtering
~~~~~~~~~~~~~~~~~~~~~~

Two new function decorators, :func:`sensitive_variables` and
:func:`sensitive_post_parameters`, were added to allow designating the
traceback frames' local variables and request's POST parameters susceptible
to contain sensitive information and that should be filtered out of error
reports.

All POST parameters are now systematically filtered out of error reports for
certain :mod:`contrib.views.auth` views (``login``, ``password_reset_confirm``,
``password_change``, and ``add_view`` and ``user_change_password`` in the
``auth`` admin) to prevent the leaking of sensitive information such as user
passwords.

You may override or customize the default filtering by writing a
:ref:`custom filter<custom-error-reports>`. Learn more on
:ref:`Filtering error reports<filtering-error-reports>`.

Extended IPv6 support
~~~~~~~~~~~~~~~~~~~~~

The previously added support for IPv6 addresses when using the runserver
management command in Django 1.3 has now been further extended by adding
a :class:`~django.db.models.fields.GenericIPAddressField` model field,
a :class:`~django.forms.fields.GenericIPAddressField` form field and
the validators :data:`~django.core.validators.validate_ipv46_address` and
:data:`~django.core.validators.validate_ipv6_address`

Translating URL patterns
~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.4 gained the ability to look for a language prefix in the URL pattern
when using the new :func:`django.conf.urls.i18n.i18n_patterns` helper function.
Additionally, it's now possible to define translatable URL patterns using
:func:`~django.utils.translation.ugettext_lazy`. See
:ref:`url-internationalization` for more information about the language prefix
and how to internationalize URL patterns.

``static`` template tag
~~~~~~~~~~~~~~~~~~~~~~~

The :mod:`staticfiles<django.contrib.staticfiles>` contrib app has now a new
:ttag:`static template tag<staticfiles-static>` to refer to files saved with
the :setting:`STATICFILES_STORAGE` storage backend. It'll use the storage
``url`` method and therefore supports advanced features such as
:ref:`serving files from a cloud service<staticfiles-from-cdn>`.

``CachedStaticFilesStorage`` storage backend
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Additional to the `static template tag`_ the
:mod:`staticfiles<django.contrib.staticfiles>` contrib app now has a
:class:`~django.contrib.staticfiles.storage.CachedStaticFilesStorage` which
caches the files it saves (when running the :djadmin:`collectstatic`
management command) by appending the MD5 hash of the file's content to the
filename. For example, the file ``css/styles.css`` would also be saved as
``css/styles.55e7cbb9ba48.css``

See the :class:`~django.contrib.staticfiles.storage.CachedStaticFilesStorage`
docs for more information.

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

Django 1.4 also includes several smaller improvements worth noting:

* A more usable stacktrace in the technical 500 page: frames in the stack
  trace which reference Django's code are dimmed out, while frames in user
  code are slightly emphasized. This change makes it easier to scan a stacktrace
  for issues in user code.

* Customizable names for :meth:`~django.template.Library.simple_tag`.

* In the documentation, a helpful :doc:`security overview </topics/security>`
  page.

* Function :func:`django.contrib.auth.models.check_password` has been moved
  to the :mod:`django.contrib.auth.utils` module. Importing it from the old
  location will still work, but you should update your imports.

* The :djadmin:`collectstatic` management command gained a ``--clear`` option
  to delete all files at the destination before copying or linking the static
  files.

* It is now possible to load fixtures containing forward references when using
  MySQL with the InnoDB database engine.

* A new 403 response handler has been added as
  ``'django.views.defaults.permission_denied'``. See the documentation
  about :ref:`the 403 (HTTP Forbidden) view<http_forbidden_view>` for more
  information.

* The :ttag:`trans` template tag now takes an optional ``as`` argument to
  be able to retrieve a translation string without displaying it but setting
  a template context variable instead.

.. _backwards-incompatible-changes-1.4:

Backwards incompatible changes in 1.4
=====================================

django.contrib.admin
~~~~~~~~~~~~~~~~~~~~

The included administration app ``django.contrib.admin`` has for a long time
shipped with a default set of static files such as JavaScript, images and
stylesheets. Django 1.3 added a new contrib app ``django.contrib.staticfiles``
to handle such files in a generic way and defined conventions for static
files included in apps.

Starting in Django 1.4 the admin's static files are now also following this
convention to make it easier to deploy the included files. In previous
versions of Django, it was also common to define a ``ADMIN_MEDIA_PREFIX``
setting to point to the URL where the admin's static files are served by a
web server. This setting has now been deprecated and replaced by the more
general setting :setting:`STATIC_URL`. Django will now expect to find the
admin static files under the URL ``<STATIC_URL>/admin/``.

If you've previously used a URL path for ``ADMIN_MEDIA_PREFIX`` (e.g.
``/media/``) simply make sure :setting:`STATIC_URL` and :setting:`STATIC_ROOT`
are configured and your web server serves the files correctly. The development
server continues to serve the admin files just like before. Don't hesitate to
consult the :doc:`static files howto </howto/static-files>` for further
details.

In case your ``ADMIN_MEDIA_PREFIX`` is set to an own domain (e.g.
``http://media.example.com/admin/``) make sure to also set your
:setting:`STATIC_URL` setting to the correct URL, for example
``http://media.example.com/``.

.. warning::

    If you're implicitely relying on the path of the admin static files on
    your server's file system when you deploy your site, you have to update
    that path. The files were moved from :file:`django/contrib/admin/media/`
    to :file:`django/contrib/admin/static/admin/`.

Removed admin icons
~~~~~~~~~~~~~~~~~~~

As part of an effort to improve the performance and usability of the admin's
vertical and horizontal "filter" widgets, some icon files were removed and
grouped into a single sprite file (``selector-icons.gif``):
``selector-add.gif``, ``selector-addall.gif``, ``selector-remove.gif``,
``selector-removeall.gif``, ``selector_stacked-add.gif`` and
``selector_stacked-remove.gif``. If you used those icons to customize the
admin then you will want to replace them with your own icons or retrieve them
from a previous release.

Compatibility with old signed data
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.3 changed the cryptographic signing mechanisms used in a number of
places in Django. While Django 1.3 kept fallbacks that would accept hashes
produced by the previous methods, these fallbacks are removed in Django 1.4.

So, if you upgrade to Django 1.4 directly from 1.2 or earlier, you may
lose/invalidate certain pieces of data that have been cryptographically signed
using an old method. To avoid this, use Django 1.3 first, for a period of time,
to allow the signed data to expire naturally. The affected parts are detailed
below, with 1) the consequences of ignoring this advice and 2) the amount of
time you need to run Django 1.3 for the data to expire or become irrelevant.

* contrib.sessions data integrity check

  * consequences: the user will be logged out, and session data will be lost.

  * time period: defined by SESSION_COOKIE_AGE.

* contrib.auth password reset hash

  * consequences: password reset links from before the upgrade will not work.

  * time period: defined by PASSWORD_RESET_TIMEOUT_DAYS.

Form related hashes — these are much shorter lifetime, and are relevant only for
the short window where a user might fill in a form generated by the pre-upgrade
Django instance, and try to submit it to the upgraded Django instance:

* contrib.comments form security hash

  * consequences: the user will see a validation error "Security hash failed".

  * time period: the amount of time you expect users to take filling out comment
    forms.

* FormWizard security hash

  * consequences: the user will see an error about the form having expired,
    and will be sent back to the first page of the wizard, losing the data
    they have inputted so far.

  * time period: the amount of time you expect users to take filling out the
    affected forms.

* CSRF check

  * Note: This is actually a Django 1.1 fallback, not Django 1.2,
    and applies only if you are upgrading from 1.1.

  * consequences: the user will see a 403 error with any CSRF protected POST
    form.

  * time period: the amount of time you expect user to take filling out
    such forms.

django.contrib.flatpages
~~~~~~~~~~~~~~~~~~~~~~~~

Starting in the 1.4 release the
:class:`~django.contrib.flatpages.middleware.FlatpageFallbackMiddleware` only
adds a trailing slash and redirects if the resulting URL refers to an existing
flatpage. For example, requesting ``/notaflatpageoravalidurl`` in a previous
version would redirect to ``/notaflatpageoravalidurl/``, which would
subsequently raise a 404. Requesting ``/notaflatpageoravalidurl`` now will
immediately raise a 404. Additionally redirects returned by flatpages are now
permanent (301 status code) to match the behavior of the
:class:`~django.middleware.common.CommonMiddleware`.

`COMMENTS_BANNED_USERS_GROUP` setting
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django's :doc:`comments app </ref/contrib/comments/index>` has historically
supported excluding the comments of a special user group, but we've never
documented the feature properly and didn't enforce the exclusion in other parts
of the app, e.g., the template tags. To fix this problem, we removed the code
from the feed class.

If you rely on the feature and want to restore the old behavior, simply use
a custom comment model manager to exclude the user group, like this::

    from django.conf import settings
    from django.contrib.comments.managers import CommentManager

    class BanningCommentManager(CommentManager):
        def get_query_set(self):
            qs = super(BanningCommentManager, self).get_query_set()
            if getattr(settings, 'COMMENTS_BANNED_USERS_GROUP', None):
                where = ['user_id NOT IN (SELECT user_id FROM auth_user_groups WHERE group_id = %s)']
                params = [settings.COMMENTS_BANNED_USERS_GROUP]
                qs = qs.extra(where=where, params=params)
            return qs

Save this model manager in your custom comment app (e.g. in
``my_comments_app/managers.py``) and add it your
:ref:`custom comment app model <custom-comment-app-api>`::

    from django.db import models
    from django.contrib.comments.models import Comment

    from my_comments_app.managers import BanningCommentManager

    class CommentWithTitle(Comment):
        title = models.CharField(max_length=300)

        objects = BanningCommentManager()

For more details, see the documentation about
:doc:`customizing the comments framework </ref/contrib/comments/custom>`.

`IGNORABLE_404_STARTS` and `IGNORABLE_404_ENDS` settings
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django can report 404 errors: see :doc:`/howto/error-reporting`.
Until Django 1.3, it was possible to exclude some URLs from the reporting
by adding prefixes to :setting:`IGNORABLE_404_STARTS` and suffixes to
:setting:`IGNORABLE_404_ENDS`.

In Django 1.4, these two settings are superseded by
:setting:`IGNORABLE_404_URLS`, which is a list of compiled regular expressions.
Django won't send an email for 404 errors on URLs that match any of them.

Furthermore, the previous settings had some rather arbitrary default values::

    IGNORABLE_404_STARTS = ('/cgi-bin/', '/_vti_bin', '/_vti_inf')
    IGNORABLE_404_ENDS = ('mail.pl', 'mailform.pl', 'mail.cgi', 'mailform.cgi',
                          'favicon.ico', '.php')

It's not Django's role to decide if your website has a legacy ``/cgi-bin/``
section or a ``favicon.ico``. As a consequence, the default values of
:setting:`IGNORABLE_404_URLS`, :setting:`IGNORABLE_404_STARTS` and
:setting:`IGNORABLE_404_ENDS` are all now empty.

If you have customized :setting:`IGNORABLE_404_STARTS` or
:setting:`IGNORABLE_404_ENDS`, or if you want to keep the old default value,
you should add the following lines in your settings file::

    import re
    IGNORABLE_404_URLS = (
        # for each <prefix> in IGNORABLE_404_STARTS
        re.compile(r'^<prefix>'),
        # for each <suffix> in IGNORABLE_404_ENDS
        re.compile(r'<suffix>$'),
    )

Don't forget to escape characters that have a special meaning in a regular
expression.

CSRF protection extended to PUT and DELETE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Previously, Django's :doc:`CSRF protection </ref/contrib/csrf/>` provided
protection against only POST requests. Since use of PUT and DELETE methods in
AJAX applications is becoming more common, we now protect all methods not
defined as safe by :rfc:`2616` i.e. we exempt GET, HEAD, OPTIONS and TRACE, and
enforce protection on everything else.

If you using PUT or DELETE methods in AJAX applications, please see the
:ref:`instructions about using AJAX and CSRF <csrf-ajax>`.

``django.core.template_loaders``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This was an alias to ``django.template.loader`` since 2005, it has been removed
without emitting a warning due to the length of the deprecation. If your code
still referenced this please use ``django.template.loader`` instead.

.. _deprecated-features-1.4:

Features deprecated in 1.4
==========================

Old styles of calling ``cache_page`` decorator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some legacy ways of calling :func:`~django.views.decorators.cache.cache_page`
have been deprecated, please see the docs for the correct way to use this
decorator.

Support for PostgreSQL versions older than 8.2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.3 dropped support for PostgreSQL versions older than 8.0 and the
relevant documents suggested to use a recent version because of performance
reasons but more importantly because end of the upstream support periods for
releases 8.0 and 8.1 was near (November 2010.)

Django 1.4 takes that policy further and sets 8.2 as the minimum PostgreSQL
version it officially supports.

Request exceptions are now always logged
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When :doc:`logging support </topics/logging/>` was added to Django in 1.3, the
admin error email support was moved into the
:class:`django.utils.log.AdminEmailHandler`, attached to the
``'django.request'`` logger. In order to maintain the established behavior of
error emails, the ``'django.request'`` logger was called only when
:setting:`DEBUG` was `False`.

To increase the flexibility of request-error logging, the ``'django.request'``
logger is now called regardless of the value of :setting:`DEBUG`, and the
default settings file for new projects now includes a separate filter attached
to :class:`django.utils.log.AdminEmailHandler` to prevent admin error emails in
`DEBUG` mode::

   'filters': {
        'require_debug_false': {
            '()': 'django.utils.log.CallbackFilter',
            'callback': lambda r: not DEBUG
        }
    },
    'handlers': {
        'mail_admins': {
            'level': 'ERROR',
            'filters': ['require_debug_false'],
            'class': 'django.utils.log.AdminEmailHandler'
        }
    },

If your project was created prior to this change, your :setting:`LOGGING`
setting will not include this new filter. In order to maintain
backwards-compatibility, Django will detect that your ``'mail_admins'`` handler
configuration includes no ``'filters'`` section, and will automatically add
this filter for you and issue a pending-deprecation warning. This will become a
deprecation warning in Django 1.5, and in Django 1.6 the
backwards-compatibility shim will be removed entirely.

The existence of any ``'filters'`` key under the ``'mail_admins'`` handler will
disable this backward-compatibility shim and deprecation warning.