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 is 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
---------------

There have been large changes to the way that CSRF protection works, detailed in
:ref:`the CSRF documentaton <ref-contrib-csrf>`.  The following are the major
changes that developers must 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, so 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 that 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 like ``{% if not %}`` or
``{% if and %}`` will throw a TemplateSyntaxError.

``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 are 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. Old-style database settings will be automatically translated to
the new-style format.

In the old-style (pre 1.2) format, there were a number of
``DATABASE_`` settings at the top level of your settings file. For
example::

    DATABASE_NAME = 'test_db'
    DATABASE_BACKEND = 'postgresl_psycopg2'
    DATABASE_USER = 'myusername'
    DATABASE_PASSWORD = 's3krit'

These settings are now contained inside 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 to reflect the fact that they are stored in a dictionary.
The sample settings given previously would now be stored using::

    DATABASES = {
        'default': {
            'NAME': 'test_db',
            'BACKEND': 'django.db.backends.postgresl_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.postgresl_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 out ``_state`` attribute of out ``__dict__``.

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

Prior to v1.2, 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, and 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.

Conversion functions has been provided which will transparently
convert functions adhering to the old prototype into functions
compatible with the new prototype. However, this conversion function
will be removed in Django 1.4, so you should upgrade your Field
definitions to use the new prototype.

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 that you wrote yourself, 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>`.

.. _deprecated-features-1.2:

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

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')
    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', 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::

    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::

    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.

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
querysets; individual objects can be saved to a specific database
by providing a ``using`` argument when you save the instance.

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

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

.. code-block:: html+django

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

...as you can now do:

.. code-block:: html+django

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

The operators supported are ``==``, ``!=``, ``<``, ``>``, ``<=``, ``>=`` and
``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 use a
cached 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 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
----------------------

The :djadmin:`test` subcommand of ``django-admin.py``, and the ``runtests.py`` 
script used to run Django's own test suite, support a new ``--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 run before the interruption.        

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

Django's :ref:`internationalization framework <topics-i18n>` has been
expanded by 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.

Added ``readonly_fields`` to ``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 along side editable fields.

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

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