1.2.txt

========================
Django 1.2 release notes
========================

*May 17, 2010.*

Welcome to Django 1.2!

Nearly a year in the making, Django 1.2 packs an impressive list of `new
features`_ and lots of bug fixes. These release notes cover the new features,
as well as important changes you'll want to be aware of when upgrading from
Django 1.1 or older versions.

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

Overview
========

Django 1.2 introduces several large, important new features, including:

    * Support for `multiple database connections`_ in a single Django instance.

    * `Model validation`_ inspired by Django's form validation.

    * Vastly `improved protection against Cross-Site Request Forgery`_ (CSRF).

    * A new `user "messages" framework`_ with support for cookie- and session-based
      message for both anonymous and authenticated users.

    * Hooks for `object-level permissions`_, `permissions for anonymous users`_,
      and `more flexible username requirements`_.

    * Customization of e-mail sending via `e-mail backends`_.

    * New :ref:`"smart" if template tag <new-in-1.2-smart-if>` which supports
      comparison operators.

.. _multiple database connections: `support for multiple databases`_
.. _improved protection against Cross-Site Request Forgery: `improved CSRF protection`_
.. _user "messages" framework: `messages framework`_
.. _more flexible username requirements: `relaxed requirements for usernames`_

These are just the highlights; full details and a complete list of features `may
be found below`_.

.. _may be found below: `what's new in django 1.2`_

.. seealso::

    `Django Advent`_ covered the release of Django 1.2 with a series of
    articles and tutorials that cover some of the new features in depth.

.. _django advent: http://djangoadvent.com/

Wherever possible these features have been introduced in a backwards-compatible
manner per :doc:`our API stability policy </misc/api-stability>` policy.

However, a handful of features *have* changed in ways that, for some users, will be
backwards-incompatible. The big changes are:

    * Support for Python 2.3 has been dropped. See the full notes
      below.

    * The new CSRF protection framework is not backwards-compatible with
      the old system. Users of the old system will not be affected until
      the old system is removed in Django 1.4.

      However, upgrading to the new CSRF protection framework requires a few
      important backwards-incompatible changes, detailed in `CSRF Protection`_,
      below.

    * Authors of custom :class:`~django.db.models.Field` subclasses should be
      aware that a number of methods have had a change in prototype, detailed
      under `get_db_prep_*() methods on Field`_, below.

    * The internals of template tags have changed somewhat; authors of custom
      template tags that need to store state (e.g. custom control flow tags)
      should ensure that their code follows the new rules for `stateful template
      tags`_

    * The :func:`~django.contrib.auth.decorators.user_passes_test`,
      :func:`~django.contrib.auth.decorators.login_required`, and
      :func:`~django.contrib.auth.decorators.permission_required`, decorators
      from :mod:`django.contrib.auth` only apply to functions and no longer
      work on methods. There's a simple one-line fix `detailed below`_.

.. _detailed below: `user_passes_test, login_required and permission_required`_

Again, these are just the big features that will affect the most users. Users
upgrading from previous versions of Django are heavily encouraged to consult
the complete list of :ref:`backwards-incompatible changes
<backwards-incompatible-changes-1.2>` and the list of :ref:`deprecated
features <deprecated-features-1.2>`.

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

While not a new feature, it's important to note that Django 1.2
introduces the first shift in our Python compatibility policy since
Django's initial public debut. Previous Django releases were tested
and supported on 2.x Python versions from 2.3 up; Django 1.2, however,
drops official support for Python 2.3. As such, the minimum Python
version required for Django is now 2.4, and Django is tested and
supported on Python 2.4, 2.5 and 2.6, and will be supported on the
as-yet-unreleased Python 2.7.

This change should affect only a small number of Django users, as most
operating-system vendors today are shipping Python 2.4 or newer as
their default version. If you're still using Python 2.3, however,
you'll need to stick to Django 1.1 until you can upgrade; per
:doc:`our support policy </internals/release-process>`, Django 1.1 will
continue to receive security support until the release of Django 1.3.

A roadmap for Django's overall 2.x Python support, and eventual
transition to Python 3.x, is currently being developed, and will be
announced prior to the release of Django 1.3.

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

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

Django 1.2 adds the ability to use :doc:`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()``.

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 :doc:`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.

Improved CSRF protection
------------------------

Django now has much improved protection against :doc:`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.

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

Django now includes a robust and configurable :doc:`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).

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 :doc:`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 :doc:`authentication
docs </topics/auth>` for more details.

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.

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 :doc:`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>`.

.. _new-in-1.2-smart-if:

"Smart" :ttag:`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>`.

Class-based template loaders
----------------------------

As part of the changes made to introduce `Template caching`_  and following
a general trend in Django, the template loaders API has been modified
to use template loading mechanisms that are encapsulated in Python classes as
opposed to functions, the only method available until Django 1.1.

All the template loaders :ref:`shipped with Django <template-loaders>` have
been ported to the new API but they still implement the function-based API and
the template core machinery still accepts function-based loaders (builtin or
third party) so there is no immediate need to modify your
:setting:`TEMPLATE_LOADERS` setting in existing projects, things will keep
working if you leave it untouched up to and including the Django 1.3 release.

If you have developed your own custom template loaders we suggest to consider
porting them to a class-based implementation because the code for backwards
compatibility with function-based loaders starts its deprecation process in
Django 1.2 and will be removed in Django 1.4.  There is a description of the
API these loader classes must implement :ref:`here
<topic-template-alternate-language>` and you can also examine the source code
of the loaders shipped with Django.

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.

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.

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

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

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

Django's :doc:`internationalization framework </topics/i18n/index>` 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>`.

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

:doc:`Syndication feeds </ref/contrib/syndication>` can now be used directly as
views in your :doc:`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.

GeoDjango
---------

The most significant new feature for :doc:`GeoDjango </ref/contrib/gis/index>`
in 1.2 is support for multiple spatial databases.  As a result,
the following :ref:`spatial database backends <spatial-backends>`
are now included:

* :mod:`django.contrib.gis.db.backends.postgis`
* :mod:`django.contrib.gis.db.backends.mysql`
* :mod:`django.contrib.gis.db.backends.oracle`
* :mod:`django.contrib.gis.db.backends.spatialite`

GeoDjango now supports the rich capabilities added
in the `PostGIS 1.5 release <http://postgis.refractions.net/documentation/manual-1.5/>`_.
New features include suppport for the the :ref:`geography type <geography-type>`
and enabling of :ref:`distance queries <distance-queries>`
with non-point geometries on geographic coordinate systems.

Support for 3D geometry fields was added, and may be enabled
by setting the :attr:`~django.contrib.gis.db.models.GeometryField.dim`
keyword to 3 in your :class:`~django.contrib.gis.db.models.GeometryField`.
The :class:`~django.contrib.gis.db.models.Extent3D` aggregate
and :meth:`~django.contrib.gis.db.models.GeoQuerySet.extent3d` ``GeoQuerySet``
method were added as a part of this feature.

The following :class:`~django.contrib.gis.db.models.GeoQuerySet`
methods are new in 1.2:

* :meth:`~django.contrib.gis.db.models.GeoQuerySet.force_rhr`
* :meth:`~django.contrib.gis.db.models.GeoQuerySet.reverse_geom`
* :meth:`~django.contrib.gis.db.models.GeoQuerySet.geohash`

The :ref:`GEOS interface <ref-geos>` was updated to use
thread-safe C library functions when available on the platform.

The :ref:`GDAL interface <ref-gdal>` now allows the user to
set a :attr:`~django.contrib.gis.gdal.Layer.spatial_filter` on
the features returned when iterating over a
:class:`~django.contrib.gis.gdal.Layer`.

Finally, :doc:`GeoDjango's documentation </ref/contrib/gis/index>` is now
included with Django's and is no longer
hosted separately at `geodjango.org <http://geodjango.org/>`_.

.. _1.2-js-assisted-inlines:

JavaScript-assisted handling of inline related objects in the admin
-------------------------------------------------------------------

If a user has JavaScript enabled in their browser, the interface for
inline objects in the admin now allows inline objects to be
dynamically added and removed. Users without JavaScript-enabled
browsers will see no change in the behavior of inline objects.

New ``now`` template tag format specifier characters: ``c`` and ``u``
---------------------------------------------------------------------

The argument to the :ttag:`now` has gained two new format characters:
``c`` to specify that a datetime value should be formatted in ISO 8601
format, and ``u`` that allows output of the microseconds part of a
datetime or time value.

These are also available in others parts like the :tfilter:`date` and
:tfilter:`time` template filters, the ``humanize`` template tag library
and the new `format localization`_ framework.

.. _format localization: `Improved localization`_

.. _backwards-incompatible-changes-1.2:

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

Wherever possible the new features above have been introduced in a
backwards-compatible manner per :doc:`our API stability policy
</misc/api-stability>` policy. This means that practically all existing
code which worked with Django 1.1 will continue to work with Django
1.2; such code will, however, begin issuing warnings (see below for
details).

However, a handful of features *have* changed in ways that, for some
users, will be immediately backwards-incompatible. Those changes are
detailed below.

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

We've made large changes to the way CSRF protection works, detailed in
:doc:`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 and
   will cease to be supported in Django 1.4).

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

Prior to Django 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 db_type(self):
            # ...

        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 db_type(self, connection):
            # ...

        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 --
``db_type`` and ``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 as soon as possible.

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 their ``Node`` subclass
have always been vulnerable to thread-safety and other issues; as of
Django 1.2, however, they may also cause problems when 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 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.

``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'). Unfortunately, flaws were discovered in the
code supporting this: 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' behavior 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. For example, 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 of you who've been following the development trunk, this
change also applies to other decorators introduced since 1.1,
including ``csrf_protect``, ``cache_control`` and anything created
using ``decorator_from_middleware``.

: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,
these strings could be used as variable names. 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 tag.

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

``LazyObject`` is an undocumented-but-often-used 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 named
``get_all_members()``. Since this could easily lead to name clashes, it has been
changed to use the standard Python introspection method, involving
``__members__`` and ``__dir__()``.

If you used ``LazyObject`` in your own code
and implemented the ``get_all_members()`` method for wrapped objects, you'll need
to make a couple of changes:

First, 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
introspection method for Python 2.6 and above. If you require support for Python
versions earlier than 2.6, add the following code to the class::

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

``__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
be prepared to handle or filter out the ``_state`` attribute.

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
comma and semicolon 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.

``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.

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

In previous versions of Django, a model's ``BooleanField`` under MySQL
would return its value as either ``1`` or ``0``, instead of ``True``
or ``False``; for most people this wasn't a problem because ``bool``
is a subclass of ``int`` in Python. In Django 1.2, however,
``BooleanField`` on MySQL correctly returns a real ``bool``.  The only
time this should ever be an issue is if you were expecting the
``repr`` of a ``BooleanField`` to print ``1`` or ``0``.

Changes to the interpretation of ``max_num`` in FormSets
--------------------------------------------------------

As part of enhancements made to the handling of FormSets, the default
value and interpretation of the ``max_num`` parameter to the
:ref:`django.forms.formsets.formset_factory() <formsets-max-num>` and
:ref:`django.forms.models.modelformset_factory()
<model-formsets-max-num>` functions has changed slightly. This
change also affects the way the ``max_num`` argument is :ref:`used for
inline admin objects <ref-contrib-admin-inline-max-num>`

Previously, the default value for ``max_num`` was ``0`` (zero).
FormSets then used the boolean value of ``max_num`` to determine if a
limit was to be imposed on the number of generated forms. The default
value of ``0`` meant that there was no default limit on the number of
forms in a FormSet.

Starting with 1.2, the default value for ``max_num`` has been changed
to ``None``, and FormSets will differentiate between a value of
``None`` and a value of ``0``. A value of ``None`` indicates that no
limit on the number of forms is to be imposed; a value of ``0``
indicates that a maximum of 0 forms should be imposed. This doesn't
necessarily mean that no forms will be displayed -- see the
:ref:`ModelFormSet documentation <model-formsets-max-num>` for more
details.

If you were manually specifying a value of ``0`` for ``max_num``, you
will need to update your FormSet and/or admin definitions.

.. seealso::

    :ref:`1.2-js-assisted-inlines`

``email_re``
------------

An undocumented regular expression 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.

.. _deprecated-features-1.2:

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

Finally, Django 1.2 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 1.2. 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 1.3, these warnings will become a ``DeprecationWarning``,
which is *not* silent. In Django 1.4 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>`.`

.. _specifying-databases:

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

Prior to Django 1.2, 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``).

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

The ``psycopg1`` library has not been updated since October 2005. As a
result, the ``postgresql`` database backend, which uses 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
:setting:`DATABASE_ENGINE` setting to use
``django.db.backends.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 :doc:`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
:doc:`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.

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 :doc:`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 :doc:`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.

GeoDjango
---------

To allow support for multiple databases, the GeoDjango database internals were
changed substantially.  The largest backwards-incompatible change is that
the module ``django.contrib.gis.db.backend`` was renamed to
:mod:`django.contrib.gis.db.backends`, where the full-fledged
:ref:`spatial database backends <spatial-backends>` now exist.  The
following sections provide information on the most-popular APIs that
were affected by these changes.

``SpatialBackend``
^^^^^^^^^^^^^^^^^^

Prior to the creation of the separate spatial backends, the
``django.contrib.gis.db.backend.SpatialBackend`` object was
provided as an abstraction to introspect on the capabilities of
the spatial database.  All of the attributes and routines provided by
``SpatialBackend`` are now a part of the ``ops`` attribute of the
database backend.

The old module ``django.contrib.gis.db.backend`` is still provided
for backwards-compatibility access to a ``SpatialBackend`` object,
which is just an alias to the ``ops`` module of the
*default* spatial database connection.

Users that were relying on undocumented modules and objects
within ``django.contrib.gis.db.backend``, rather the abstractions
provided by ``SpatialBackend``, are required to modify their code.
For example, the following import which would work in 1.1 and
below::

    from django.contrib.gis.db.backend.postgis import PostGISAdaptor

Would need to be changed::

    from django.db import connection
    PostGISAdaptor = connection.ops.Adapter

``SpatialRefSys`` and ``GeometryColumns`` models
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In previous versions of GeoDjango, :mod:`django.contrib.gis.db.models`
had ``SpatialRefSys`` and ``GeometryColumns`` models for querying
the OGC spatial metadata tables ``spatial_ref_sys`` and ``geometry_columns``,
respectively.

While these aliases are still provided, they are only for the
*default* database connection and exist only if the default connection
is using a supported spatial database backend.

.. note::

    Because the table structure of the OGC spatial metadata tables
    differs across spatial databases, the ``SpatialRefSys`` and
    ``GeometryColumns`` models can no longer be associated with
    the ``gis`` application name.  Thus, no models will be returned
    when using the ``get_models`` method in the following example::

        >>> from django.db.models import get_app, get_models
        >>> get_models(get_app('gis'))
        []

To get the correct ``SpatialRefSys`` and ``GeometryColumns``
for your spatial database use the methods provided by the spatial backend::

     >>> from django.db import connections
     >>> SpatialRefSys = connections['my_spatialite'].ops.spatial_ref_sys()
     >>> GeometryColumns = connections['my_postgis'].ops.geometry_columns()

.. note::

    When using the models returned from the ``spatial_ref_sys()`` and
    ``geometry_columns()`` method, you'll still need to use the
    correct database alias when querying on the non-default connection.
    In other words, to ensure that the models in the example above
    use the correct database::

        sr_qs = SpatialRefSys.objects.using('my_spatialite').filter(...)
        gc_qs = GeometryColumns.objects.using('my_postgis').filter(...)

Language code ``no``
--------------------

The currently used language code for Norwegian Bokmål ``no`` is being
replaced by the more common language code ``nb``.

Function-based template loaders
-------------------------------

Django 1.2 changes the template loading mechanism to use a class-based
approach. Old style function-based template loaders will still work, but should
be updated to use the new :ref:`class-based template loaders
<topic-template-alternate-language>`.