Django 2.1 release notes

August 1, 2018

Welcome to Django 2.1!

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 2.0 or earlier. We’ve dropped some features that have reached the end of their deprecation cycle, and we’ve begun the deprecation process for some features.

如果你要更新现有的项目，请看 升级 Django 到最新的版本 指南。

Python 兼容性

Django 2.1 supports Python 3.5, 3.6, and 3.7. Django 2.0 is the last version to support Python 3.4. We highly recommend and only officially support the latest release of each series.

What’s new in Django 2.1

Model “view” permission

A “view” permission is added to the model Meta.default_permissions. The new permissions will be created automatically when running migrate.

This allows giving users read-only access to models in the admin. ModelAdmin.has_view_permission() is new. The implementation is backwards compatible in that there isn’t a need to assign the “view” permission to allow users who have the “change” permission to edit objects.

There are a couple of backwards incompatible considerations.

次要特性

django.contrib.admin

django.contrib.auth

django.contrib.gis

django.contrib.sessions

缓存

CSRF

表单

  • The widget for ImageField now renders with the HTML attribute accept="image/*".

国际化

  • Added the get_supported_language_variant() function.
  • Untranslated strings for territorial language variants now use the translations of the generic language. For example, untranslated pt_BR strings use pt translations.

管理命令

  • The new inspectdb --include-views option allows creating models for database views.
  • The BaseCommand class now uses a custom help formatter so that the standard options like --verbosity or --settings appear last in the help output, giving a more prominent position to subclassed command’s options.

迁移

  • Added support for serialization of functools.partialmethod objects.
  • To support frozen environments, migrations may be loaded from .pyc files.

模型

请求和响应

  • Added HttpRequest.get_full_path_info().
  • Added the samesite argument to HttpResponse.set_cookie() to allow setting the SameSite cookie flag.
  • The new as_attachment argument for FileResponse sets the Content-Disposition header to make the browser ask if the user wants to download the file. FileResponse also tries to set the Content-Type and Content-Length headers where appropriate.

模板

  • The new json_script filter safely outputs a Python object as JSON, wrapped in a <script> tag, ready for use with JavaScript.

测试

  • Added test Client support for 307 and 308 redirects.
  • The test Client now serializes a request data dictionary as JSON if content_type='application/json'. You can customize the JSON encoder with test client’s json_encoder parameter.
  • The new SimpleTestCase.assertWarnsMessage() method is a simpler version of assertWarnsRegex().

Backwards incompatible changes in 2.1

数据库后端 API

本节介绍了第三方数据库后端可能需要的更改。

  • To adhere to PEP 249, exceptions where a database doesn’t support a feature are changed from NotImplementedError to django.db.NotSupportedError.
  • Renamed the allow_sliced_subqueries database feature flag to allow_sliced_subqueries_with_in.
  • DatabaseOperations.distinct_sql() now requires an additional params argument and returns a tuple of SQL and parameters instead of an SQL string.
  • DatabaseFeatures.introspected_boolean_field_type is changed from a method to a property.

django.contrib.gis

  • Support for SpatiaLite 4.0 is removed.

Dropped support for MySQL 5.5

The end of upstream support for MySQL 5.5 is December 2018. Django 2.1 supports MySQL 5.6 and higher.

Dropped support for PostgreSQL 9.3

The end of upstream support for PostgreSQL 9.3 is September 2018. Django 2.1 supports PostgreSQL 9.4 and higher.

Removed BCryptPasswordHasher from the default PASSWORD_HASHERS setting

If you used bcrypt with Django 1.4 or 1.5 (before BCryptSHA256PasswordHasher was added in Django 1.6), you might have some passwords that use the BCryptPasswordHasher hasher.

You can check if that’s the case like this:

  1. from django.contrib.auth import get_user_model
  2. User = get_user_model()
  3. User.objects.filter(password__startswith='bcrypt$$')

If you want to continue to allow those passwords to be used, you’ll have to define the PASSWORD_HASHERS setting (if you don’t already) and include 'django.contrib.auth.hashers.BCryptPasswordHasher'.

Moved wrap_label widget template context variable

To fix the lack of <label> when using RadioSelect and CheckboxSelectMultiple with MultiWidget, the wrap_label context variable now appears as an attribute of each option. For example, in a custom input_option.html template, change {% if wrap_label %} to {% if widget.wrap_label %}.

SameSite cookies

The cookies used for django.contrib.sessions, django.contrib.messages, and Django’s CSRF protection now set the SameSite flag to Lax by default. Browsers that respect this flag won’t send these cookies on cross-origin requests. If you rely on the old behavior, set the SESSION_COOKIE_SAMESITE and/or CSRF_COOKIE_SAMESITE setting to None.

Considerations for the new model “view” permission

Custom admin forms need to take the view-only case into account

With the new “view” permission, existing custom admin forms may raise errors when a user doesn’t have the change permission because the form might access nonexistent fields. Fix this by overriding ModelAdmin.get_form() and checking if the user has the “change” permissions and returning the default form if not:

  1. class MyAdmin(admin.ModelAdmin):
  2.     def get_form(self, request, obj=None, **kwargs):
  3.         if not self.has_change_permission(request, obj):
  4.             return super().get_form(request, obj, **kwargs)
  5.         return CustomForm

New default view permission could allow unwanted access to admin views

If you have a custom permission with a codename of the form view_<modelname>, the new view permission handling in the admin will allow view access to the changelist and detail pages for those models. If this is unwanted, you must change your custom permission codename.

杂项

  • The minimum supported version of mysqlclient is increased from 1.3.3 to 1.3.7.
  • Support for SQLite < 3.7.15 is removed.
  • The date format of Set-Cookie‘s Expires directive is changed to follow RFC 7231#section-7.1.1.1 instead of Netscape’s cookie standard. Hyphens present in dates like Tue, 25-Dec-2018 22:26:13 GMT are removed. This change should be merely cosmetic except perhaps for antiquated browsers that don’t parse the new format.
  • allowed_hosts is now a required argument of private API django.utils.http.is_safe_url().
  • The multiple attribute rendered by the SelectMultiple widget now uses HTML5 boolean syntax rather than XHTML’s multiple="multiple".
  • HTML rendered by form widgets no longer includes a closing slash on void elements, e.g. <br>. This is incompatible within XHTML, although some widgets already used aspects of HTML5 such as boolean attributes.
  • The value of SelectDateWidget‘s empty options is changed from 0 to an empty string, which mainly may require some adjustments in tests that compare HTML.
  • User.has_usable_password() and the is_password_usable() function no longer return False if the password is None or an empty string, or if the password uses a hasher that’s not in the PASSWORD_HASHERS setting. This undocumented behavior was a regression in Django 1.6 and prevented users with such passwords from requesting a password reset. Audit your code to confirm that your usage of these APIs don’t rely on the old behavior.
  • Since migrations are now loaded from .pyc files, you might need to delete them if you’re working in a mixed Python 2 and Python 3 environment.
  • Using None as a JSONField lookup value now matches objects that have the specified key and a null value rather than objects that don’t have the key.
  • The admin CSS class field-box is renamed to fieldBox to prevent conflicts with the class given to model fields named “box”.
  • Since the admin’s actions.html, change_list_results.html, date_hierarchy.html, pagination.html, prepopulated_fields_js.html, search_form.html, and submit_line.html templates can now be overridden per app or per model, you may need to rename existing templates with those names that were written for a different purpose.
  • QuerySet.raw() now caches its results like regular querysets. Use iterator() if you don’t want caching.
  • The database router allow_relation() method is called in more cases. Improperly written routers may need to be updated accordingly.
  • Translations are no longer deactivated before running management commands. If your custom command requires translations to be deactivated (for example, to insert untranslated content into the database), use the new @no_translations decorator.
  • Management commands no longer allow the abbreviated forms of the --settings and --pythonpath arguments.
  • The private django.db.models.sql.constants.QUERY_TERMS constant is removed. The get_lookup() and get_lookups() methods of the Lookup Registration API may be suitable alternatives. Compared to the QUERY_TERMS constant, they allow your code to also account for any custom lookups that have been registered.
  • Compatibility with py-bcrypt is removed as it’s unmaintained. Use bcrypt instead.

Features deprecated in 2.1

杂项

  • The ForceRHR GIS function is deprecated in favor of the new ForcePolygonCW function.
  • django.utils.http.cookie_date() is deprecated in favor of http_date(), which follows the format of the latest RFC.
  • {% load staticfiles %} and {% load admin_static %} are deprecated in favor of {% load static %}, which works the same.
  • django.contrib.staticfiles.templatetags.static() is deprecated in favor of django.templatetags.static.static().
  • Support for InlineModelAdmin.has_add_permission() methods that don’t accept obj as the second positional argument will be removed in Django 3.0.

Features removed in 2.1

These features have reached the end of their deprecation cycle and are removed in Django 2.1. See Features deprecated in 1.11 for details, including how to remove usage of these features.

  • contrib.auth.views.login(), logout(), password_change(), password_change_done(), password_reset(), password_reset_done(), password_reset_confirm(), and password_reset_complete() are removed.
  • The extra_context parameter of contrib.auth.views.logout_then_login() is removed.
  • django.test.runner.setup_databases() is removed.
  • django.utils.translation.string_concat() is removed.
  • django.core.cache.backends.memcached.PyLibMCCache no longer supports passing pylibmc behavior settings as top-level attributes of OPTIONS.
  • The host parameter of django.utils.http.is_safe_url() is removed.
  • Silencing of exceptions raised while rendering the {% include %} template tag is removed.
  • DatabaseIntrospection.get_indexes() is removed.
  • The authenticate() method of authentication backends requires request as the first positional argument.
  • The django.db.models.permalink() decorator is removed.
  • The USE_ETAGS setting is removed. CommonMiddleware and django.utils.cache.patch_response_headers() no longer set ETags.
  • The Model._meta.has_auto_field attribute is removed.
  • url()‘s support for inline flags in regular expression groups ((?i), (?L), (?m), (?s), and (?u)) is removed.
  • Support for Widget.render() methods without the renderer argument is removed.