# Documentazione Django 6.0.7

# Note di rilascio di Django 2.1

1 Agosto 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.

See the Come aggiornare Django ad una nuova versione guide if you’re updating an existing project.

## Compatibilità con Python

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.

### Minor features

#### `django.contrib.admin`

- `ModelAdmin.search_fields` now accepts any lookup such as `field__exact`.

- jQuery is upgraded from version 2.2.3 to 3.3.1.

- The new `ModelAdmin.delete_queryset()` method allows customizing the deletion process of the «delete selected objects» action.

- You can now override the default admin site.

- The new `ModelAdmin.sortable_by` attribute and `ModelAdmin.get_sortable_by()` method allow limiting the columns that can be sorted in the change list page.

- The `admin_order_field` attribute for elements in `ModelAdmin.list_display` may now be a query expression.

- The new `ModelAdmin.get_deleted_objects()` method allows customizing the deletion process of the delete view and the «delete selected» action.

- The `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 (besides overridden globally).

- The admin change list and change form object tools can now be overridden per app, per model, or globally with `change_list_object_tools.html` and `change_form_object_tools.html` templates.

- `InlineModelAdmin.has_add_permission()` is now passed the parent object as the second positional argument, `obj`.

- Admin actions may now specify permissions to limit their availability to certain users.

#### `django.contrib.auth`

- `createsuperuser` now gives a prompt to allow bypassing the `AUTH_PASSWORD_VALIDATORS` checks.

#### `django.contrib.gis`

- The new `GEOSGeometry.buffer_with_style()` method is a version of `buffer()` that allows customizing the style of the buffer.

- `OpenLayersWidget` is now based on OpenLayers 4.6.5 (previously 3.20.1).

#### `django.contrib.sessions`

- Added the `SESSION_COOKIE_SAMESITE` setting to set the `SameSite` cookie flag on session cookies.

#### Cache

- The local-memory cache backend now uses a least-recently-used (LRU) culling strategy rather than a pseudo-random one.

- The new `touch()` method of the low-level cache API updates the timeout of cache keys.

#### CSRF

- Added the `CSRF_COOKIE_SAMESITE` setting to set the `SameSite` cookie flag on CSRF cookies.

#### I Form

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

#### Internationalization

- 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.

#### Management Commands

- 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.

#### Migrations

- Added support for serialization of `functools.partialmethod` objects.

- To support frozen environments, migrations may be loaded from `.pyc` files.

#### Modelli

- Models can now use `__init_subclass__()` from PEP 487.

- A `BinaryField` may now be set to `editable=True` if you wish to include it in model forms.

- A number of new text database functions are added: `Chr`, `Left`, `LPad`, `LTrim`, `Ord`, `Repeat`, `Replace`, `Right`, `RPad`, `RTrim`, and `Trim`.

- The new `TruncWeek` function truncates `DateField` and `DateTimeField` to the Monday of a week.

- Query expressions can now be negated using a minus sign.

- `QuerySet.order_by()` and `distinct(*fields)` now support using field transforms.

- `BooleanField` can now be `null=True`. This is encouraged instead of `NullBooleanField`, which will likely be deprecated in the future.

- The new `QuerySet.explain()` method displays the database’s execution plan of a queryset’s query.

- `QuerySet.raw()` now supports `prefetch_related()`.

#### Requests and Responses

- 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.

#### Template

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

#### Tests

- 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

### Database backend API

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

- 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:

    from django.contrib.auth import get_user_model

    User = get_user_model()
    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:

    class MyAdmin(admin.ModelAdmin):
        def get_form(self, request, obj=None, **kwargs):
            if not self.has_change_permission(request, obj):
                return super().get_form(request, obj, **kwargs)
            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.

### Miscellanea

- 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 `django.contrib.postgres.fields.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

### Miscellanea

- 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.