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Django 4.0 release notes - UNDER DEVELOPMENT

Expected December 2021

Welcome to Django 4.0!

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 3.2 or earlier. We’ve begun the deprecation process for some features.

See the Upgrading Django to a newer 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.

The Django 3.2.x series is the last to support Python 3.6 and 3.7.

What’s new in Django 4.0

Functional unique constraints

The new *expressions positional argument of UniqueConstraint() enables creating functional unique constraints on expressions and database functions. For example:

from django.db import models
from django.db.models import UniqueConstraint
from django.db.models.functions import Lower


class MyModel(models.Model):
    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)

    class Meta:
        indexes = [
            UniqueConstraint(
                Lower('first_name'),
                Lower('last_name').desc(),
                name='first_last_name_unique',
            ),
        ]

Functional unique constraints are added to models using the Meta.constraints option.

Minor features

django.contrib.admin

  • The admin/base.html template now has a new block header which contains the admin site header.
  • The new ModelAdmin.get_formset_kwargs() method allows customizing the keyword arguments passed to the constructor of a formset.
  • The navigation sidebar now has a quick filter toolbar.
  • The new context variable model which contains the model class for each model is added to the AdminSite.each_context() method.
  • The new ModelAdmin.search_help_text attribute allows specifying a descriptive text for the search box.

django.contrib.admindocs

  • The admindocs now allows esoteric setups where ROOT_URLCONF is not a string.
  • The model section of the admindocs now shows cached properties.

django.contrib.auth

django.contrib.gis

  • Added support for SpatiaLite 5.
  • GDALRaster now allows creating rasters in any GDAL virtual filesystem.

django.contrib.postgres

django.contrib.staticfiles

Cache

  • …

CSRF

Decorators

  • …

Email

  • …

Error Reporting

  • …

File Storage

  • …

File Uploads

  • …

Forms

  • ModelChoiceField now includes the provided value in the params argument of a raised ValidationError for the invalid_choice error message. This allows custom error messages to use the %(value)s placeholder.

Generic Views

  • …

Internationalization

  • …

Logging

  • …

Management Commands

Migrations

  • …

Models

  • New QuerySet.contains(obj) method returns whether the queryset contains the given object. This tries to perform the query in the simplest and fastest way possible.
  • The new precision argument of the Round() database function allows specifying the number of decimal places after rounding.
  • QuerySet.bulk_create() now sets the primary key on objects when using SQLite 3.35+.
  • DurationField now supports multiplying and dividing by scalar values on SQLite.

Requests and Responses

Security

  • …

Serialization

  • …

Signals

  • The new stdout argument for pre_migrate() and post_migrate() signals allows redirecting output to a stream-like object. It should be preferred over sys.stdout and print() when emitting verbose output in order to allow proper capture when testing.

Templates

  • …

Tests

URLs

  • …

Utilities

  • …

Validators

  • …

Backwards incompatible changes in 4.0

Database backend API

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

  • DatabaseOperations.year_lookup_bounds_for_date_field() and year_lookup_bounds_for_datetime_field() methods now take the optional iso_year argument in order to support bounds for ISO-8601 week-numbering years.
  • The second argument of DatabaseSchemaEditor._unique_sql() and _create_unique_sql() methods is now fields instead of columns.

django.contrib.gis

  • Support for PostGIS 2.3 is removed.
  • Support for GDAL 2.0 and GEOS 3.5 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.

CSRF_TRUSTED_ORIGINS changes

Format change

Values in the CSRF_TRUSTED_ORIGINS setting must include the scheme (e.g. 'http://' or 'https://') instead of only the hostname.

Also, values that started with a dot, must now also include an asterisk before the dot. For example, change '.example.com' to 'https://*.example.com'.

A system check detects any required changes.

Configuring it may now be required

As CSRF protection now consults the Origin header, you may need to set CSRF_TRUSTED_ORIGINS, particularly if you allow requests from subdomains by setting CSRF_COOKIE_DOMAIN (or SESSION_COOKIE_DOMAIN if CSRF_USE_SESSIONS is enabled) to a value starting with a dot.

SecurityMiddleware no longer sets the X-XSS-Protection header

The SecurityMiddleware no longer sets the X-XSS-Protection header if the SECURE_BROWSER_XSS_FILTER setting is True. The setting is removed.

Most modern browsers don’t honor the X-XSS-Protection HTTP header. You can use Content-Security-Policy without allowing 'unsafe-inline' scripts instead.

If you want to support legacy browsers and set the header, use this line in a custom middleware:

response.headers.setdefault('X-XSS-Protection', '1; mode=block')

Migrations autodetector changes

The migrations autodetector now uses model states instead of model classes. Also, migration operations for ForeignKey and ManyToManyField fields no longer specify attributes which were not passed to the fields during initialization.

As a side-effect, running makemigrations might generate no-op AlterField operations for ManyToManyField and ForeignKey fields in some cases.

Miscellaneous

  • Support for cx_Oracle < 7.0 is removed.
  • To allow serving a Django site on a subpath without changing the value of STATIC_URL, the leading slash is removed from that setting (now 'static/') in the default startproject template.
  • The AdminSite method for the admin index view is no longer decorated with never_cache when accessed directly, rather than via the recommended AdminSite.urls property, or AdminSite.get_urls() method.
  • Unsupported operations on a sliced queryset now raise TypeError instead of AssertionError.
  • The undocumented django.test.runner.reorder_suite() function is renamed to reorder_tests(). It now accepts an iterable of tests rather than a test suite, and returns an iterator of tests.
  • Calling FileSystemStorage.delete() with an empty name now raises ValueError instead of AssertionError.
  • Calling EmailMultiAlternatives.attach_alternative() or EmailMessage.attach() with an invalid content or mimetype arguments now raise ValueError instead of AssertionError.
  • assertHTMLEqual() no longer considers a non-boolean attribute without a value equal to an attribute with the same name and value.
  • Tests that fail to load, for example due to syntax errors, now always match when using test --tag.
  • The undocumented django.contrib.admin.utils.lookup_needs_distinct() function is renamed to lookup_spawns_duplicates().
  • The undocumented HttpRequest.get_raw_uri() method is removed. The HttpRequest.build_absolute_uri() method may be a suitable alternative.
  • The object argument of undocumented ModelAdmin.log_addition(), log_change(), and log_deletion() methods is renamed to obj.
  • RssFeed, Atom1Feed, and their subclasses now emit elements with no content as self-closing tags.
  • NodeList.render() no longer casts the output of render() method for individual nodes to a string. Node.render() should always return a string as documented.

Features deprecated in 4.0

Time zone support

In order to follow good practice, the default value of the USE_TZ setting will change from False to True, and time zone support will be enabled by default, in Django 5.0.

Note that the default settings.py file created by django-admin startproject includes USE_TZ = True since Django 1.4.

You can set USE_TZ to False in your project settings before then to opt-out.

Miscellaneous

  • SERIALIZE test setting is deprecated as it can be inferred from the databases with the serialized_rollback option enabled.
  • The undocumented django.utils.baseconv module is deprecated.
  • The undocumented django.utils.datetime_safe module is deprecated.
  • The default sitemap protocol for sitemaps built outside the context of a request will change from 'http' to 'https' in Django 5.0.

Features removed in 4.0

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

See Features deprecated in 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 Features deprecated in 3.1 for details on these changes, including how to remove usage of these features.

  • The PASSWORD_RESET_TIMEOUT_DAYS setting is removed.
  • The 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_response 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.
Release notes
Django 3.2.5 release notes
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