============================================
Django 4.0 release notes - UNDER DEVELOPMENT
============================================

*Expected December 2021*

Welcome to Django 4.0!

These release notes cover the :ref:`new features <whats-new-4.0>`, as well as
some :ref:`backwards incompatible changes <backwards-incompatible-4.0>` you'll
want to be aware of when upgrading from Django 3.2 or earlier. We've
:ref:`begun the deprecation process for some features
<deprecated-features-4.0>`.

See the :doc:`/howto/upgrade-version` guide if you're updating an existing
project.

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

Django 4.0 supports Python 3.8, 3.9, and 3.10. We **highly recommend** and only
officially support the latest release of each series.

.. _whats-new-4.0:

What's new in Django 4.0
========================

Minor features
--------------

:mod:`django.contrib.admin`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The ``admin/base.html`` template now has a new block ``header`` which
  contains the admin site header.

:mod:`django.contrib.admindocs`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The admindocs now allows esoteric setups where :setting:`ROOT_URLCONF` is not
  a string.

:mod:`django.contrib.auth`
~~~~~~~~~~~~~~~~~~~~~~~~~~

* The default iteration count for the PBKDF2 password hasher is increased from
  260,000 to 320,000.

:mod:`django.contrib.contenttypes`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.gis`
~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.messages`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.postgres`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The PostgreSQL backend now supports connecting by a service name. See
  :ref:`postgresql-connection-settings` for more details.

:mod:`django.contrib.redirects`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sessions`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sitemaps`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.sites`
~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.staticfiles`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

:mod:`django.contrib.syndication`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ...

Cache
~~~~~

* ...

CSRF
~~~~

* ...

Decorators
~~~~~~~~~~

* ...

Email
~~~~~

* ...

Error Reporting
~~~~~~~~~~~~~~~

* ...

File Storage
~~~~~~~~~~~~

* ...

File Uploads
~~~~~~~~~~~~

* ...

Forms
~~~~~

* :class:`~django.forms.ModelChoiceField` now includes the provided value in
  the ``params`` argument of a raised
  :exc:`~django.core.exceptions.ValidationError` for the ``invalid_choice``
  error message. This allows custom error messages to use the ``%(value)s``
  placeholder.

Generic Views
~~~~~~~~~~~~~

* ...

Internationalization
~~~~~~~~~~~~~~~~~~~~

* ...

Logging
~~~~~~~

* ...

Management Commands
~~~~~~~~~~~~~~~~~~~

* The :djadmin:`runserver` management command now supports the
  :option:`--skip-checks` option.

Migrations
~~~~~~~~~~

* ...

Models
~~~~~~

* ...

Requests and Responses
~~~~~~~~~~~~~~~~~~~~~~

* ...

Security
~~~~~~~~

* ...

Serialization
~~~~~~~~~~~~~

* ...

Signals
~~~~~~~

* ...

Templates
~~~~~~~~~

* ...

Tests
~~~~~

* ...

URLs
~~~~

* ...

Utilities
~~~~~~~~~

* ...

Validators
~~~~~~~~~~

* ...

.. _backwards-incompatible-4.0:

Backwards incompatible changes in 4.0
=====================================

Database backend API
--------------------

This section describes changes that may be needed in third-party database
backends.

* ...

:mod:`django.contrib.gis`
-------------------------

* Support for PostGIS 2.3 is removed.

Dropped support for PostgreSQL 9.6
----------------------------------

Upstream support for PostgreSQL 9.6 ends in November 2021. Django 4.0 supports
PostgreSQL 10 and higher.

Dropped support for Oracle 12.2 and 18c
---------------------------------------

Upstream support for Oracle 12.2 ends in March 2022 and for Oracle 18c it ends
in June 2021. Django 3.2 will be supported until April 2024. Django 4.0
officially supports Oracle 19c.

Miscellaneous
-------------

* Support for ``cx_Oracle`` < 7.0 is removed.

.. _deprecated-features-4.0:

Features deprecated in 4.0
==========================

Miscellaneous
-------------

* ...

Features removed in 4.0
=======================

These features have reached the end of their deprecation cycle and are removed
in Django 4.0.

See :ref:`deprecated-features-3.0` for details on these changes, including how
to remove usage of these features.

* ``django.utils.http.urlquote()``, ``urlquote_plus()``, ``urlunquote()``, and
  ``urlunquote_plus()`` are removed.

* ``django.utils.encoding.force_text()`` and ``smart_text()`` are removed.

* ``django.utils.translation.ugettext()``, ``ugettext_lazy()``,
  ``ugettext_noop()``, ``ungettext()``, and ``ungettext_lazy()`` are removed.

* ``django.views.i18n.set_language()`` doesn't set the user language in
  ``request.session`` (key ``_language``).

* ``alias=None`` is required in the signature of
  ``django.db.models.Expression.get_group_by_cols()`` subclasses.

* ``django.utils.text.unescape_entities()`` is removed.

* ``django.utils.http.is_safe_url()`` is removed.

See :ref:`deprecated-features-3.1` for details on these changes, including how
to remove usage of these features.

* The ``PASSWORD_RESET_TIMEOUT_DAYS`` setting is removed.

* The :lookup:`isnull` lookup no longer allows using non-boolean values as the
  right-hand side.

* The ``django.db.models.query_utils.InvalidQuery`` exception class is removed.

* The ``django-admin.py`` entry point is removed.

* The ``HttpRequest.is_ajax()`` method is removed.

* Support for the pre-Django 3.1 encoding format of cookies values used by
  ``django.contrib.messages.storage.cookie.CookieStorage`` is removed.

* Support for the pre-Django 3.1 password reset tokens in the admin site (that
  use the SHA-1 hashing algorithm) is removed.

* Support for the pre-Django 3.1 encoding format of sessions is removed.

* Support for the pre-Django 3.1 ``django.core.signing.Signer`` signatures
  (encoded with the SHA-1 algorithm) is removed.

* Support for the pre-Django 3.1 ``django.core.signing.dumps()`` signatures
  (encoded with the SHA-1 algorithm) in ``django.core.signing.loads()`` is
  removed.

* Support for the pre-Django 3.1 user sessions (that use the SHA-1 algorithm)
  is removed.

* The ``get_request`` argument for
  ``django.utils.deprecation.MiddlewareMixin.__init__()`` is required and
  doesn't accept ``None``.

* The ``providing_args`` argument for ``django.dispatch.Signal`` is removed.

* The ``length`` argument for ``django.utils.crypto.get_random_string()`` is
  required.

* The ``list`` message for ``ModelMultipleChoiceField`` is removed.

* Support for passing raw column aliases to ``QuerySet.order_by()`` is removed.

* The ``NullBooleanField`` model field is removed, except for support in
  historical migrations.

* ``django.conf.urls.url()`` is removed.

* The ``django.contrib.postgres.fields.JSONField`` model field is removed,
  except for support in historical migrations.

* ``django.contrib.postgres.fields.jsonb.KeyTransform`` and
  ``django.contrib.postgres.fields.jsonb.KeyTextTransform`` are removed.

* ``django.contrib.postgres.forms.JSONField`` is removed.

* The ``{% ifequal %}`` and ``{% ifnotequal %}`` template tags are removed.

* The ``DEFAULT_HASHING_ALGORITHM`` transitional setting is removed.
