wagtail/docs/releases/4.0.md

# Wagtail 4.0 release notes - IN DEVELOPMENT

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## What's new

### Other features

 * Add clarity to confirmation when being asked to convert an external link to an internal one (Thijs Kramer)
 * Convert various pages in the documentation to Markdown (Khanh Hoang, Vu Pham, Daniel Kirkham, LB (Ben) Johnston, Thiago Costa de Souza)
 * Add `base_url_path` to `ModelAdmin` so that the default URL structure of app_label/model_name can be overridden (Vu Pham, Khanh Hoang)
 * Add `full_url` to the API output of `ImageRenditionField` (Paarth Agarwal)
 * Use `InlinePanel`'s label when available for field comparison label (Sandil Ranasinghe)
 * Drop support for Safari 13 by removing left/right positioning in favour of CSS logical properties (Thibaud Colas)
 * Use `FormData` instead of jQuery's `form.serialize` when editing documents or images just added so that additional fields can be better supported (Stefan Hammer)
 * Add informational Codecov status checks for GitHub CI pipelines (Tom Hu)
 * Make it possible to reuse and customise Wagtail’s fonts with CSS variables (LB (Ben) Johnston)
 * Add better handling and informative developer errors for cross linking URLS (e.g. success after add) in generic views `wagtail.admin.views.generic` (Matt Westcott)
 * Introduce `wagtail.admin.widgets.chooser.BaseChooser` to make it easier to build custom chooser inputs (Matt Westcott)
 * Introduce JavaScript chooser module, including a SearchController class which encapsulates the standard pattern of re-rendering the results panel in response to search queries and pagination (Matt Westcott)
 * Add ability to select multiple items at once within bulk actions selections when holding shift on subsequent clicks (Hitansh Shah)

### Bug fixes

 * Fix issue where `ModelAdmin` index listings with export list enabled would show buttons with an incorrect layout (Josh Woodcock)
 * Fix typo in `ResumeWorkflowActionFormatter` message (Stefan Hammer)
 * Throw a meaningful error when saving an image to an unrecognised image format (Christian Franke)
 * Remove extra padding for headers with breadcrumbs on mobile viewport (Steven Steinwand)
 * Replace `PageRevision` with generic `Revision` model (Sage Abdullah)
 * Ensure the upgrade notification request for the latest release, which can be disabled via the `WAGTAIL_ENABLE_UPDATE_CHECK` sends the referrer origin with `strict-origin-when-cross-origin` (Karl Hobley)
 * Ensure radio buttons / checkboxes display vertically under Django 4.0 (Matt Westcott)
 * Ensure that custom document or image models support custom tag models (Matt Westcott)
 * Ensure comments use translated values for their placeholder text (Stefan Hammer)


## Upgrade considerations

### `base_url_path` keyword argument added to AdminURLHelper

The `wagtail.contrib.modeladmin.helpers.AdminURLHelper` class now accepts a `base_url_path` keyword argument on its constructor. Custom subclasses of this class should be updated to accept this keyword argument.

### Dropped support for Safari 13

Safari 13 will no longer be officially supported as of this release, this deviates the current support for the last 3 version of Safari by a few months and was required to add better support for RTL languages.

### `PageRevision` replaced with `Revision`

The `PageRevision` model has been replaced with a generic `Revision` model. If you use the `PageRevision` model in your code, make sure that:

 * Creation of `PageRevision` objects should be updated to create `Revision` objects using the page's `id` as the `object_id`, the default `Page` model's content type as the `base_content_type`, and the page's specific content type as the `content_type`.
 * Queries that use the `PageRevision.objects` manager should be updated to use the `Revision.page_revisions` manager.
 * `Revision` queries that use `Page.id` should be updated to cast the `Page.id` to a string before using it in the query (e.g. by using `str()` or `Cast("page_id", output_field=CharField())`).
 * `Page` queries that use `PageRevision.page_id` should be updated to cast the `Revision.object_id` to an integer before using it in the query (e.g. by using `int()` or `Cast("object_id", output_field=IntegerField())`).
 * Access to `PageRevision.page` should be updated to `Revision.content_object`.

If you maintain a package across multiple Wagtail versions that includes a model with a `ForeignKey` to the `PageRevision` model, you can create a helper function to correctly resolve the model depending on the installed Wagtail version, for example:

```python
from django.db import models
from wagtail import VERSION as WAGTAIL_VERSION


def get_revision_model():
    if WAGTAIL_VERSION >= (4, 0):
        return "wagtailcore.Revision"
    return "wagtailcore.PageRevision"


class MyModel(models.Model):
    # Before
    # revision = models.ForeignKey("wagtailcore.PageRevision")
    revision = models.ForeignKey(get_revision_model(), on_delete=models.CASCADE)
```


### `AdminChooser` replaced with `BaseChooser`

Custom choosers should no longer use `wagtail.admin.widgets.chooser.AdminChooser` which has been replaced with `wagtail.admin.widgets.chooser.BaseChooser`.