1.3.txt

============================================
Django 1.3 release notes - UNDER DEVELOPMENT
============================================

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

Django 1.3 includes a number of nifty `new features`_, lots of bug
fixes, some minor `backwards incompatible changes`_ and an easy
upgrade path from Django 1.2.

.. _new features: `What's new in Django 1.3`_

.. _backwards incompatible changes: backwards-incompatible-changes-1.3_

What's new in Django 1.3
========================

Class-based views
~~~~~~~~~~~~~~~~~

Django 1.3 adds a framework that allows you to use a class as a view.
This means you can compose a view out of a collection of methods that
can be subclassed and overridden to provide common views of data without
having to write too much code.

Analogs of all the old function-based generic views have been
provided, along with a completely generic view base class that can be
used as the basis for reusable applications that can be easily
extended.

See :doc:`the documentation on Class-based Generic Views</topics/class-based-views>`
for more details. There is also a document to help you :doc:`convert
your function-based generic views to class-based
views</topics/generic-views-migration>`.

Logging
~~~~~~~

Django 1.3 adds framework-level support for Python's logging module.
This means you can now easily configure and control logging as part of
your Django project. A number of logging handlers and logging calls
have been added to Django's own code as well -- most notably, the
error emails sent on a HTTP 500 server error are now handled as a
logging activity. See :doc:`the documentation on Django's logging
interface </topics/logging>` for more details.

Extended static files handling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.3 ships with a new contrib app ``'django.contrib.staticfiles'``
to help developers handle the static media files (images, CSS, Javascript,
etc.) that are needed to render a complete web page.

In previous versions of Django, it was common to place static assets in
:setting:`MEDIA_ROOT` along with user-uploaded files, and serve them both at
:setting:`MEDIA_URL`. Part of the purpose of introducing the ``staticfiles``
app is to make it easier to keep static files separate from user-uploaded
files. For this reason, you will probably want to make your
:setting:`MEDIA_ROOT` and :setting:`MEDIA_URL` different from your
:setting:`STATIC_ROOT` and :setting:`STATIC_URL`. You will need to
arrange for serving of files in :setting:`MEDIA_ROOT` yourself;
``staticfiles`` does not deal with user-uploaded media at all.

See the :doc:`reference documentation of the app </ref/contrib/staticfiles>`
for more details or learn how to :doc:`manage static files
</howto/static-files>`.

``unittest2`` support
~~~~~~~~~~~~~~~~~~~~~

Python 2.7 introduced some major changes to the unittest library,
adding some extremely useful features. To ensure that every Django
project can benefit from these new features, Django ships with a
copy of unittest2_, a copy of the Python 2.7 unittest library,
backported for Python 2.4 compatibility.

To access this library, Django provides the
``django.utils.unittest`` module alias. If you are using Python
2.7, or you have installed unittest2 locally, Django will map the
alias to the installed version of the unittest library. Otherwise,
Django will use it's own bundled version of unittest2.

To use this alias, simply use::

    from django.utils import unittest

wherever you would have historically used::

    import unittest

If you want to continue to use the base unittest libary, you can --
you just won't get any of the nice new unittest2 features.

.. _unittest2: http://pypi.python.org/pypi/unittest2

Transaction context managers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Users of Python 2.5 and above may now use :ref:`transaction management functions
<transaction-management-functions>` as `context managers`_. For example::

    with transaction.autocommit():
        # ...

.. _context managers: http://docs.python.org/glossary.html#term-context-manager

For more information, see :ref:`transaction-management-functions`.

Configurable delete-cascade
~~~~~~~~~~~~~~~~~~~~~~~~~~~

:class:`~django.db.models.ForeignKey` and
:class:`~django.db.models.OneToOneField` now accept an
:attr:`~django.db.models.ForeignKey.on_delete` argument to customize behavior
when the referenced object is deleted. Previously, deletes were always
cascaded; available alternatives now include set null, set default, set to any
value, protect, or do nothing.

For more information, see the :attr:`~django.db.models.ForeignKey.on_delete`
documentation.

Contextual markers and comments for translatable strings
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For translation strings with ambiguous meaning, you can now
use the ``pgettext`` function to specify the context of the string.

And if you just want to add some information for translators, you
can also add special translator comments in the source.

For more information, see :ref:`contextual-markers` and
:ref:`translator-comments`.

TemplateResponse
~~~~~~~~~~~~~~~~

It can sometimes be beneficial to allow decorators or middleware to
modify a response *after* it has been constructed by the view. For
example, you may want to change the template that is used, or put
additional data into the context.

However, you can't (easily) modify the content of a basic
:class:`~django.http.HttpResponse` after it has been constructed. To
overcome this limitation, Django 1.3 adds a new
:class:`~django.template.TemplateResponse` class. Unlike basic
:class:`~django.http.HttpResponse` objects,
:class:`~django.template.TemplateResponse` objects retain the details
of the template and context that was provided by the view to compute
the response. The final output of the response is not computed until
it is needed, later in the response process.

For more details, see the :ref:`documentation </ref/template-response>`
on the :class:`~django.template.TemplateResponse` class.

Caching changes
~~~~~~~~~~~~~~~

Django 1.3 sees the introduction of several improvements to the
Django's caching infrastructure.

Firstly, Django now supports multiple named caches. In the same way
that Django 1.2 introduced support for multiple database connections,
Django 1.3 allows you to use the new :setting:`CACHES` setting to
define multiple named cache connections.

Secondly, :ref:`Versioning <cache_versioning>`, :ref:`site-wide
prefixing <cache_key_prefixing>` and :ref:`transformation
<cache_key_transformation>` has been added to the cache API.

Lastly, support for pylibmc_ has been added to the memcached cache
backend.

For more details, see the :ref:`documentation on
caching in Django<topics/cache>`.

.. _pylibmc: http://sendapatch.se/projects/pylibmc/

Everything else
~~~~~~~~~~~~~~~

Django :doc:`1.1 <1.1>` and :doc:`1.2 <1.2>` added
lots of big ticket items to Django, like multiple-database support,
model validation, and a session-based messages framework. However,
this focus on big features came at the cost of lots of smaller
features.

To compensate for this, the focus of the Django 1.3 development
process has been on adding lots of smaller, long standing feature
requests. These include:

    * Improved tools for accessing and manipulating the current Site.

    * A :class:`~django.test.client.RequestFactory` for mocking
      requests in tests.

    * A new test assertion --
      :meth:`~django.test.client.Client.assertNumQueries` -- making it
      easier to test the database activity associated with a view.

    * Support for lookups spanning relations in admin's ``list_filter``.

    * Support for _HTTPOnly cookies.

    * :meth:`mail_admins()` and :meth:`mail_managers()` now support
      easily attaching HTML content to messages.

    * :class:`EmailMessage` now supports CC's.

    * Error emails now include more of the detail and formatting of
      the debug server error page.

    * :meth:`simple_tag` now accepts a :attr:`takes_context` argument,
      making it easier to write simple template tags that require
      access to template context.

    * A new :meth:`~django.shortcuts.render()` shortcut -- an
      alternative to :meth:`~django.shortcuts.render_to_response()`
      providing a :class:`~django.template.RequestContext` by
      default.

.. _HTTPOnly: http://www.owasp.org/index.php/HTTPOnly

.. _backwards-incompatible-changes-1.3:

Backwards-incompatible changes in 1.3
=====================================

PasswordInput default rendering behavior
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The :class:`~django.forms.PasswordInput` form widget, intended for use
with form fields which represent passwords, accepts a boolean keyword
argument ``render_value`` indicating whether to send its data back to
the browser when displaying a submitted form with errors. Prior to
Django 1.3, this argument defaulted to ``True``, meaning that the
submitted password would be sent back to the browser as part of the
form. Developers who wished to add a bit of additional security by
excluding that value from the redisplayed form could instantiate a
:class:`~django.forms.PasswordInput` passing ``render_value=False`` .

Due to the sensitive nature of passwords, however, Django 1.3 takes
this step automatically; the default value of ``render_value`` is now
``False``, and developers who want the password value returned to the
browser on a submission with errors (the previous behavior) must now
explicitly indicate this. For example::

    class LoginForm(forms.Form):
        username = forms.CharField(max_length=100)
        password = forms.CharField(widget=forms.PasswordInput(render_value=True))

Clearable default widget for FileField
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.3 now includes a ``ClearableFileInput`` form widget in addition to
``FileInput``. ``ClearableFileInput`` renders with a checkbox to clear the
field's value (if the field has a value and is not required); ``FileInput``
provided no means for clearing an existing file from a ``FileField``.

``ClearableFileInput`` is now the default widget for a ``FileField``, so
existing forms including ``FileField`` without assigning a custom widget will
need to account for the possible extra checkbox in the rendered form output.

To return to the previous rendering (without the ability to clear the
``FileField``), use the ``FileInput`` widget in place of
``ClearableFileInput``. For instance, in a ``ModelForm`` for a hypothetical
``Document`` model with a ``FileField`` named ``document``::

    from django import forms
    from myapp.models import Document

    class DocumentForm(forms.ModelForm):
        class Meta:
            model = Document
            widgets = {'document': forms.FileInput}

New index on database session table
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Prior to Django 1.3, the database table used by the database backend
for the :doc:`sessions </topics/http/sessions>` app had no index on
the ``expire_date`` column. As a result, date-based queries on the
session table -- such as the query that is needed to purge old
sessions -- would be very slow if there were lots of sessions.

If you have an existing project that is using the database session
backend, you don't have to do anything to accommodate this change.
However, you may get a significant performance boost if you manually
add the new index to the session table. The SQL that will add the
index can be found by running the :djadmin:`sqlindexes` admin
command::

    python manage.py sqlindexes sessions

No more naughty words
~~~~~~~~~~~~~~~~~~~~~

Django has historically provided (and enforced) a list of profanities.
The :doc:`comments app </ref/contrib/comments/index>` has enforced this
list of profanities, preventing people from submitting comments that
contained one of those profanities.

Unfortunately, the technique used to implement this profanities list
was woefully naive, and prone to the `Scunthorpe problem`_. Fixing the
built in filter to fix this problem would require significant effort,
and since natural language processing isn't the normal domain of a web
framework, we have "fixed" the problem by making the list of
prohibited words an empty list.

If you want to restore the old behavior, simply put a
``PROFANITIES_LIST`` setting in your settings file that includes the
words that you want to prohibit (see the `commit that implemented this
change`_ if you want to see the list of words that was historically
prohibited). However, if avoiding profanities is important to you, you
would be well advised to seek out a better, less naive approach to the
problem.

.. _Scunthorpe problem: http://en.wikipedia.org/wiki/Scunthorpe_problem
.. _commit that implemented this change: http://code.djangoproject.com/changeset/13996

Localflavor changes
~~~~~~~~~~~~~~~~~~~

Django 1.3 introduces the following backwards-incompatible changes to
local flavors:

    * Indonesia (id) -- The province "Nanggroe Aceh Darussalam (NAD)"
      has been removed from the province list in favor of the new
      official designation "Aceh (ACE)".

FormSet updates
~~~~~~~~~~~~~~~

In Django 1.3 ``FormSet`` creation behavior is modified slightly. Historically
the class didn't make a distinction between not being passed data and being
passed empty dictionary. This was inconsistent with behavior in other parts of
the framework. Starting with 1.3 if you pass in empty dictionary the
``FormSet`` will raise a ``ValidationError``.

For example with a ``FormSet``::

    >>> class ArticleForm(Form):
    ...     title = CharField()
    ...     pub_date = DateField()
    >>> ArticleFormSet = formset_factory(ArticleForm)

the following code will raise a ``ValidationError``::

    >>> ArticleFormSet({})
    Traceback (most recent call last):
    ...
    ValidationError: [u'ManagementForm data is missing or has been tampered with']

if you need to instantiate an empty ``FormSet``, don't pass in the data or use
``None``::

    >>> formset = ArticleFormSet()
    >>> formset = ArticleFormSet(data=None)



.. _deprecated-features-1.3:

Features deprecated in 1.3
==========================

Django 1.3 deprecates some features from earlier releases.
These features are still supported, but will be gradually phased out
over the next few release cycles.

Code taking advantage of any of the features below will raise a
``PendingDeprecationWarning`` in Django 1.3. This warning will be
silent by default, but may be turned on using Python's `warnings
module`_, or by running Python with a ``-Wd`` or `-Wall` flag.

.. _warnings module: http://docs.python.org/library/warnings.html

In Django 1.4, these warnings will become a ``DeprecationWarning``,
which is *not* silent. In Django 1.5 support for these features will
be removed entirely.

.. seealso::

    For more details, see the documentation :doc:`Django's release process
    </internals/release-process>` and our :doc:`deprecation timeline
    </internals/deprecation>`.

``mod_python`` support
~~~~~~~~~~~~~~~~~~~~~~

The ``mod_python`` library has not had a release since 2007 or a commit since
2008. The Apache Foundation board voted to remove ``mod_python`` from the set
of active projects in its version control repositories, and its lead developer
has shifted all of his efforts toward the lighter, slimmer, more stable, and
more flexible ``mod_wsgi`` backend.

If you are currently using the ``mod_python`` request handler, you
should redeploy your Django projects using another request handler.
:doc:`mod_wsgi </howto/deployment/modwsgi>` is the request handler
recommended by the Django project, but :doc:`FastCGI
</howto/deployment/fastcgi>` is also supported. Support for
``mod_python`` deployment will be removed in Django 1.5.

Function-based generic views
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As a result of the introduction of class-based generic views, the
function-based generic views provided by Django have been deprecated.
The following modules and the views they contain have been deprecated:

      * :mod:`django.views.generic.create_update`
      * :mod:`django.views.generic.date_based`
      * :mod:`django.views.generic.list_detail`
      * :mod:`django.views.generic.simple`

Test client response ``template`` attribute
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django's :ref:`test client <test-client>` returns
:class:`~django.test.client.Response` objects annotated with extra testing
information. In Django versions prior to 1.3, this included a
:attr:`~django.test.client.Response.template` attribute containing information
about templates rendered in generating the response: either None, a single
:class:`~django.template.Template` object, or a list of
:class:`~django.template.Template` objects. This inconsistency in return values
(sometimes a list, sometimes not) made the attribute difficult to work with.

In Django 1.3 the :attr:`~django.test.client.Response.template` attribute is
deprecated in favor of a new :attr:`~django.test.client.Response.templates`
attribute, which is always a list, even if it has only a single element or no
elements.

``DjangoTestRunner``
~~~~~~~~~~~~~~~~~~~~

As a result of the introduction of support for unittest2, the features
of :class:`django.test.simple.DjangoTestRunner` (including fail-fast
and Ctrl-C test termination) have been made redundant. In view of this
redundancy, :class:`~django.test.simple.DjangoTestRunner` has been
turned into an empty placeholder class, and will be removed entirely
in Django 1.5.

Changes to :ttag:`url` and :ttag:`ssi`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Most template tags will allow you to pass in either constants or
variables as arguments -- for example::

    {% extends "base.html" %}

allows you to specify a base template as a constant, but if you have a
context variable ``templ`` that contains the value ``base.html``::

    {% extends templ %}

is also legal.

However, due to an accident of history, the :ttag:`url` and
:ttag:`ssi` are different. These tags use the second, quoteless
syntax, but interpret the argument as a constant. This means it isn't
possible to use a context variable as the target of a :ttag:`url` and
:ttag:`ssi` tag.

Django 1.3 marks the start of the process to correct this historical
accident. Django 1.3 adds a new template library -- ``future`` -- that
provides alternate implementations of the :ttag:`url` and :ttag:`ssi`
template tags. This ``future`` library implement behavior that makes
the handling of the first argument consistent with the handling of all
other variables. So, an existing template that contains::

    {% url sample %}

should be replaced with::

    {% load url from future %}
    {% url 'sample' %}

The tags implementing the old behavior have been deprecated, and in
Django 1.5, the old behavior will be replaced with the new behavior.
To ensure compatibility with future versions of Django, existing
templates should be modified to use the new ``future`` libraries and
syntax.

Changes to the login methods of the admin
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In previous version the admin app defined login methods in multiple locations
and ignored the almost identical implementation in the already used auth app.
A side effect of this duplication was the missing adoption of the changes made
in r12634_ to support a broader set of characters for usernames.

This release refactores the admin's login mechanism to use a subclass of the
:class:`~django.contrib.auth.forms.AuthenticationForm` instead of a manual
form validation. The previously undocumented method
``'django.contrib.admin.sites.AdminSite.display_login_form'`` has been removed
in favor of a new :attr:`~django.contrib.admin.AdminSite.login_form`
attribute.

.. _r12634: http://code.djangoproject.com/changeset/12634

``reset`` and ``sqlreset`` management commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Those commands have been deprecated. The ``flush`` and ``sqlflush`` commands
can be used to delete everything. You can also use ALTER TABLE or DROP TABLE
statements manually.