django/docs/releases/1.8.txt

============================================
Django 1.8 release notes - UNDER DEVELOPMENT
============================================

Welcome to Django 1.8!

These release notes cover the `new features`_, as well as some `backwards
incompatible changes`_ you'll want to be aware of when upgrading from Django
1.6 or older versions. We've also dropped some features, which are detailed in
:ref:`our deprecation plan <deprecation-removed-in-1.8>`, and we've `begun the
deprecation process for some features`_.

.. _`new features`: `What's new in Django 1.8`_
.. _`backwards incompatible changes`: `Backwards incompatible changes in 1.8`_
.. _`begun the deprecation process for some features`: `Features deprecated in 1.8`_

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

Like Django 1.7, Django 1.8 requires Python 2.7 or above, though we
**highly recommend** the latest minor release.

What's new in Django 1.8
========================

...

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

:mod:`django.contrib.admin`
^^^^^^^^^^^^^^^^^^^^^^^^^^^

* :class:`~django.contrib.admin.ModelAdmin` now has a
  :meth:`~django.contrib.admin.ModelAdmin.has_module_permission`
  method to allow limiting access to the module on the admin index page.

:mod:`django.contrib.auth`
^^^^^^^^^^^^^^^^^^^^^^^^^^

* Authorization backends can now raise
  :class:`~django.core.exceptions.PermissionDenied` in
  :meth:`~django.contrib.auth.models.User.has_perm`
  and :meth:`~django.contrib.auth.models.User.has_module_perms`
  to short-circuit permission checking.
* :class:`~django.contrib.auth.forms.PasswordResetForm` now
  has a method :meth:`~django.contrib.auth.forms.PasswordResetForm.send_email`
  that can be overridden to customize the mail to be sent.
* The ``max_length`` of :attr:`Permission.name
  <django.contrib.auth.models.Permission.name>` has been increased from 50 to
  255 characters. Please run the database migration.

:mod:`django.contrib.formtools`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* A :doc:`form wizard </ref/contrib/formtools/form-wizard>` using the
  :class:`~django.contrib.formtools.wizard.views.CookieWizardView` will now ignore
  an invalid cookie, and the wizard will restart from the first step. An invalid
  cookie can occur in cases of intentional manipulation, but also after a secret
  key change. Previously, this would raise ``WizardViewCookieModified``, a
  ``SuspiciousOperation``, causing an exception for any user with an invalid cookie
  upon every request to the wizard, until the cookie is removed.

:mod:`django.contrib.gis`
^^^^^^^^^^^^^^^^^^^^^^^^^^

* Compatibility shims for ``SpatialRefSys`` and ``GeometryColumns`` changed in
  Django 1.2 have been removed.

:mod:`django.contrib.messages`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* ...

:mod:`django.contrib.redirects`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* ...

:mod:`django.contrib.sessions`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* Session cookie is now deleted after
  :meth:`~django.contrib.sessions.backends.base.SessionBase.flush()` is called.

:mod:`django.contrib.sitemaps`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* The new :attr:`Sitemap.i18n <django.contrib.sitemaps.Sitemap.i18n>` attribute
  allows you to generate a sitemap based on the :setting:`LANGUAGES` setting.

:mod:`django.contrib.sites`
^^^^^^^^^^^^^^^^^^^^^^^^^^^

* ...

:mod:`django.contrib.staticfiles`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* ...

:mod:`django.contrib.syndication`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* ...

Cache
^^^^^

* ...

Email
^^^^^

* :ref:`Email backends <topic-email-backends>` now support the context manager
  protocol for opening and closing connections.

File Storage
^^^^^^^^^^^^

* ...

File Uploads
^^^^^^^^^^^^

* ...

Forms
^^^^^

* Form widgets now render attributes with a value of ``True`` or ``False``
  as HTML5 boolean attributes.

* The new :meth:`~django.forms.Form.has_error()` method allows checking
  if a specific error has happened.

* If :attr:`~django.forms.Form.required_css_class` is defined on a form, then
  the ``<label>`` tags for required fields will have this class present in its
  attributes.

* The rendering of non-field errors in unordered lists (``<ul>``) now includes
  ``nonfield`` in its list of classes to distinguish them from field-specific
  errors.

* :class:`~django.forms.Field` now accepts a
  :attr:`~django.forms.Field.label_suffix` argument, which will override the
  form's :attr:`~django.forms.Form.label_suffix`. This enables customizing the
  suffix on a per-field basis — previously it wasn't possible to override
  a form's :attr:`~django.forms.Form.label_suffix` while using  shortcuts such
  as ``{{ form.as_p }}`` in templates.

* :class:`~django.forms.extras.widgets.SelectDateWidget` now accepts an
  :attr:`~django.forms.extras.widgets.SelectDateWidget.empty_label` argument, which will
  override the top list choice label when :class:`~django.forms.DateField` is not required.

Internationalization
^^^^^^^^^^^^^^^^^^^^

* :setting:`FORMAT_MODULE_PATH` can now be a list of strings representing
  module paths. This allows importing several format modules from different
  reusable apps. It also allows overriding those custom formats in your main
  Django project.

Management Commands
^^^^^^^^^^^^^^^^^^^

* :djadmin:`dumpdata` now has the option :djadminopt:`--output` which allows
  specifying the file to which the serialized data is written.

* :djadmin:`makemessages` and :djadmin:`compilemessages` now have the option
  :djadminopt:`--exclude` which allows exclusion of specific locales from
  processing.

* The :djadminopt:`--ignorenonexistent` option of the :djadmin:`loaddata`
  management command now ignores data for models that no longer exist.

* :djadmin:`runserver` now uses daemon threads for faster reloading.

Models
^^^^^^

* Django now logs at most 9000 queries in ``connections.queries``, in order
  to prevent excessive memory usage in long-running processes in debug mode.

* There is now a model ``Meta`` option to define a
  :attr:`default related name <django.db.models.Options.default_related_name>`
  for all relational fields of a model.

* Pickling models and querysets across different versions of Django isn't
  officially supported (it may work, but there's no guarantee). An extra
  variable that specifies the current Django version is now added to the
  pickled state of models and querysets, and Django raises a ``RuntimeWarning``
  when these objects are unpickled in a different version than the one in
  which they were pickled.

* Added :meth:`Model.from_db() <django.db.models.Model.from_db()>` which
  Django uses whenever objects are loaded using the ORM. The method allows
  customizing model loading behavior.

Signals
^^^^^^^

* Exceptions from the ``(receiver, exception)`` tuples returned by
  :meth:`Signal.send_robust() <django.dispatch.Signal.send_robust>` now have
  their traceback attached as a ``__traceback__`` attribute.

Templates
^^^^^^^^^

* ...

Requests and Responses
^^^^^^^^^^^^^^^^^^^^^^

* ``WSGIRequest`` now respects paths starting with ``//``.

* The :meth:`HttpRequest.build_absolute_uri()
  <django.http.HttpRequest.build_absolute_uri>` method now handles paths
  starting with ``//`` correctly.

* If :setting:`DEBUG` is ``True`` and a request raises a
  :exc:`~django.core.exceptions.SuspiciousOperation`, the response will be
  rendered with a detailed error page.

* The ``query_string`` argument of :class:`~django.http.QueryDict` is now
  optional, defaulting to ``None``, so a blank ``QueryDict`` can now be
  instantiated with ``QueryDict()`` instead of ``QueryDict(None)`` or
  ``QueryDict('')``.

* The ``GET`` and ``POST`` attributes of an :class:`~django.http.HttpRequest`
  object are now :class:`~django.http.QueryDict`\s rather than dictionaries,
  and the ``FILES`` attribute is now a ``MultiValueDict``.
  This brings this class into line with the documentation and with
  ``WSGIRequest``.

Tests
^^^^^

* The ``count`` argument was added to
  :meth:`~django.test.SimpleTestCase.assertTemplateUsed`. This allows you to
  assert that a template was rendered a specific number of times.

* The new :meth:`~django.test.SimpleTestCase.assertJSONNotEqual` assertion
  allows you to test that two JSON fragments are not equal.

* Added the ability to preserve the test database by adding the
  :djadminopt:`--keepdb` flag.

* Added the :attr:`~django.test.Response.resolver_match` attribute to test
  client responses.

Validators
^^^^^^^^^^

* ...

Backwards incompatible changes in 1.8
=====================================

.. warning::

    In addition to the changes outlined in this section, be sure to review the
    :ref:`deprecation plan <deprecation-removed-in-1.8>` for any features that
    have been removed. If you haven't updated your code within the
    deprecation timeline for a given feature, its removal may appear as a
    backwards incompatible change.

Related object operations are run in a transaction
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some operations on related objects such as
:meth:`~django.db.models.fields.related.RelatedManager.add()` or
:ref:`direct assignment<direct-assignment>` ran multiple data modifying
queries without wrapping them in transactions. To reduce the risk of data
corruption, all data modifying methods that affect multiple related objects
(i.e. ``add()``, ``remove()``, ``clear()``, and :ref:`direct assignment
<direct-assignment>`) now perform their data modifying queries from within a
transaction, provided your database supports transactions.

This has one backwards incompatible side effect, signal handlers triggered from
these methods are now executed within the method's transaction and any
exception in a signal handler will prevent the whole operation.

Unassigning unsaved objects to relations raises an error
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Assigning unsaved objects to a :class:`~django.db.models.ForeignKey`,
:class:`~django.contrib.contenttypes.fields.GenericForeignKey`, and
:class:`~django.db.models.OneToOneField` now raises a :exc:`ValueError`.

Previously, the assignment of an unsaved object would be silently ignored.
For example::

    >>> book = Book.objects.create(name="Django")
    >>> book.author = Author(name="John")
    >>> book.author.save()
    >>> book.save()

    >>> Book.objects.get(name="Django")
    >>> book.author
    >>>

Now, an error will be raised to prevent data loss::

    >>> book.author = Author(name="john")
    Traceback (most recent call last):
    ...
    ValueError: Cannot assign "<Author: John>": "Author" instance isn't saved in the database.

Management commands that only accept positional arguments
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you have written a custom management command that only accepts positional
arguments and you didn't specify the
:attr:`~django.core.management.BaseCommand.args` command variable, you might
get an error like ``Error: unrecognized arguments: ...``, as variable parsing
is now based on :py:mod:`argparse` which doesn't implicitly accept positional
arguments. You can make your command backwards compatible by simply setting the
:attr:`~django.core.management.BaseCommand.args` class variable. However, if
you don't have to keep compatibility with older Django versions, it's better to
implement the new :meth:`~django.core.management.BaseCommand.add_arguments`
method as described in :doc:`/howto/custom-management-commands`.

Custom test management command arguments through test runner
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The method to add custom arguments to the `test` management command through the
test runner has changed. Previously, you could provide an `option_list` class
variable on the test runner to add more arguments (à la :py:mod:`optparse`).
Now to implement the same behavior, you have to create an
``add_arguments(cls, parser)`` class method on the test runner and call
``parser.add_argument`` to add any custom arguments, as parser is now an
:py:class:`argparse.ArgumentParser` instance.

Model check ensures auto-generated column names are within limits specified by database
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A field name that's longer than the column name length supported by a database
can create problems. For example, with MySQL you'll get an exception trying to
create the column, and with PostgreSQL the column name is truncated by the
database (you may see a warning in the PostgreSQL logs).

A model check has been introduced to better alert users to this scenario before
the actual creation of database tables.

If you have an existing model where this check seems to be a false positive,
for example on PostgreSQL where the name was already being truncated, simply
use :attr:`~django.db.models.Field.db_column` to specify the name that's being
used.

The check also applies to the columns generated in an implicit
``ManyToManyField.through`` model. If you run into an issue there, use
:attr:`~django.db.models.ManyToManyField.through` to create an explicit model
and then specify :attr:`~django.db.models.Field.db_column` on its column(s)
as needed.

Query relation lookups now check object types
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Querying for model lookups now checks if the object passed is of correct type
and raises a :exc:`ValueError` if not. Previously, Django didn't care if the
object was of correct type; it just used the object's related field attribute
(e.g. ``id``) for the lookup. Now, an error is raised to prevent incorrect
lookups::

    >>> book = Book.objects.create(name="Django")
    >>> book = Book.objects.filter(author=book)
    Traceback (most recent call last):
    ...
    ValueError: Cannot query "<Book: Django>": Must be "Author" instance.

Miscellaneous
~~~~~~~~~~~~~

* ``connections.queries`` is now a read-only attribute.

* Database connections are considered equal only if they're the same object.
  They aren't hashable any more.

* :class:`~django.middleware.gzip.GZipMiddleware` used to disable compression
  for some content types when the request is from Internet Explorer, in order
  to work around a bug in IE6 and earlier. This behavior could affect
  performance on IE7 and later. It was removed.

* ``URLField.to_python`` no longer adds a trailing slash to pathless URLs.

* ``django.contrib.gis`` dropped support for GEOS 3.1 and GDAL 1.6.

* The :tfilter:`length` template filter now returns ``0`` for an undefined
  variable, rather than an empty string.

* Support for SpatiaLite < 2.4 has been dropped.

.. _deprecated-features-1.8:

Features deprecated in 1.8
==========================

Loading ``cycle`` and ``firstof`` template tags from ``future`` library
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Django 1.6 introduced ``{% load cycle from future %}`` and
``{% load firstof from future %}`` syntax for forward compatibility of the
:ttag:`cycle` and :ttag:`firstof` template tags. This syntax is now deprecated
and will be removed in Django 2.0. You can simply remove the
``{% load ... from future %}`` tags.

``django.conf.urls.patterns()``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In the olden days of Django, it was encouraged to reference views as strings
in ``urlpatterns``::

    urlpatterns = patterns('',
        url('^$', 'myapp.views.myview'),
    )

and Django would magically import ``myapp.views.myview`` internally and turn
the string into a real function reference. In order to reduce repetition when
referencing many views from the same module, the ``patterns()`` function takes
a required initial ``prefix`` argument which is prepended to all
views-as-strings in that set of ``urlpatterns``::

    urlpatterns = patterns('myapp.views',
        url('^$', 'myview'),
        url('^other/$', 'otherview'),
    )

In the modern era, we have updated the tutorial to instead recommend importing
your views module and referencing your view functions (or classes) directly.
This has a number of advantages, all deriving from the fact that we are using
normal Python in place of "Django String Magic": the errors when you mistype a
view name are less obscure, IDEs can help with autocompletion of view names,
etc.

So these days, the above use of the ``prefix`` arg is much more likely to be
written (and is better written) as::

    from myapp import views

    urlpatterns = patterns('',
        url('^$', views.myview),
        url('^other/$', views.otherview),
    )

Thus ``patterns()`` serves little purpose and is a burden when teaching new users
(answering the newbie's question "why do I need this empty string as the first
argument to ``patterns()``?"). For these reasons, we are deprecating it.
Updating your code is as simple as ensuring that ``urlpatterns`` is a list of
:func:`django.conf.urls.url` instances. For example::

    from django.conf.urls import url
    from myapp import views

    urlpatterns = [
        url('^$', views.myview),
        url('^other/$', views.otherview),
    ]

``django.test.SimpleTestCase.urls``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The attribute :attr:`SimpleTestCase.urls <django.test.SimpleTestCase.urls>`
for specifying URLconf configuration in tests has been deprecated and will be
removed in Django 2.0. Use :func:`@override_settings(ROOT_URLCONF=...)
<django.test.override_settings>` instead.

``prefix`` argument to :func:`~django.conf.urls.i18n.i18n_patterns`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Related to the previous item, the ``prefix`` argument to
:func:`django.conf.urls.i18n.i18n_patterns` has been deprecated. Simply pass a
list of :func:`django.conf.urls.url` instances instead.

Using an incorrect count of unpacked values in the :ttag:`for` template tag
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Using an incorrect count of unpacked values in :ttag:`for` tag will raise an
exception rather than fail silently in Django 2.0.

Passing a dotted path to :func:`~django.core.urlresolvers.reverse()` and :ttag:`url`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reversing URLs by Python path is an expensive operation as it causes the
path being reversed to be imported. This behavior has also resulted in a
`security issue`_. Use :ref:`named URL patterns <naming-url-patterns>`
for reversing instead.

If you are using :mod:`django.contrib.sitemaps`, add the ``name`` argument to
the ``url`` that references :func:`django.contrib.sitemaps.views.sitemap`::

    url(r'^sitemap\.xml$', 'django.contrib.sitemaps.views.sitemap',
        {'sitemaps': sitemaps}, name='django.contrib.sitemaps.views.sitemap')

to ensure compatibility when reversing by Python path is removed in Django 2.0.

Similarly for GIS sitemaps, add ``name='django.contrib.gis.sitemaps.views.kml'``
or ``name='django.contrib.gis.sitemaps.views.kmz'``.

.. _security issue: https://www.djangoproject.com/weblog/2014/apr/21/security/#s-issue-unexpected-code-execution-using-reverse

Extending management command arguments through ``Command.option_list``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Management commands now use :py:mod:`argparse` instead of :py:mod:`optparse` to
parse command-line arguments passed to commands. This also means that the way
to add custom arguments to commands has changed: instead of extending the
``option_list`` class list, you should now override the
:meth:`~django.core.management.BaseCommand.add_arguments` method and add
arguments through ``argparse.add_argument()``. See
:ref:`this example <custom-commands-options>` for more details.

``django.core.management.NoArgsCommand``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The class :class:`~django.core.management.NoArgsCommand` is now deprecated and
will be removed in Django 2.0. Use :class:`~django.core.management.BaseCommand`
instead, which takes no arguments by default.

``cache_choices`` option of ``ModelChoiceField`` and ``ModelMultipleChoiceField``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

:class:`~django.forms.ModelChoiceField` and
:class:`~django.forms.ModelMultipleChoiceField` took an undocumented, untested
option ``cache_choices``. This cached querysets between multiple renderings of
the same ``Form`` object. This option is subject to an accelerated deprecation
and will be removed in Django 1.9.

``django.template.resolve_variable()``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The function has been informally marked as "Deprecated" for some time. Replace
``resolve_variable(path, context)`` with
``django.template.Variable(path).resolve(context)``.