ForeignKeyRawIdWidget doesn't include vForeignKeyRawIdAdminField class when custom class passed in attrs

[Kevin Marsh]

I had a situation where I wanted to add an extra class to the ForeignKeyRawIdWidget widget. I noticed that doing something like:

attrs = {"class": "myAdditionalClass"}
widget = ForeignKeyRawIdWidget(rel, admin_site, attrs=attrs)

resulted in the widget not having the required vForeignKeyRawIdAdminField class since under the hood ForeignKeyRawIdWidget.get_context does something like:

context["widget"]["attrs"].setdefault("class", "vForeignKeyRawIdAdminField")

meaning the rendered <input /> looks like:

<input class="myAdditionalClass" ...

instead of:

<input class="myAdditionalClass vForeignKeyRawIdAdminField" ...

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Note that this same issue applies to the ManyToManyRawIdWidget and corresponding vManyToManyRawIdAdminField class.

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I'm not sure if ForeignKeyRawIdWidget/ManyToManyRawIdWidget is meant to be public, but it'd be nice if we could resolve this in the source. Currently I can work around this by simply doing:

attrs = {"class": "myAdditionalClass vForeignKeyRawIdAdminField"}
widget = ForeignKeyRawIdWidget(rel, admin_site, attrs=attrs)

I can create a PR based on a similar solution in the patch (and also fix ManyToManyRawIdWidget) if this gets accepted.

[Mariusz Felisiak]

I don't see any issue here, TBH. As far as I'm aware, attributes passed in attrs override default values for all widgets (not only widgets defined in django.contrib.admin.widgets), any change to this logic would be backward incompatible.

[Kevin Marsh]

Replying to Mariusz Felisiak:

Thanks Mariusz, hopefully at least this ticket will serve as instructions for others about how to ensure the JS in the widget still works when adding additional classes (although is at risk of breaking if vForeignKeyRawIdAdminField is ever renamed in a new version of Django).

As far as I'm aware, attributes passed in attrs override default values for all widgets

Not sure that's entirely true, eg. I think something like FilteredSelectMultiple just ignores any "class" attr:

class FilteredSelectMultipleWidgetTest(SimpleTestCase):
    #... rest of existing test class
    def test_render_ignores_additional_attrs(self):
        # This widget ignores any class override in `attrs`
        w = widgets.FilteredSelectMultiple("test", False, attrs={"class": "myAdditionalClass"})
        self.assertHTMLEqual(
            w.render("test", "test"),
            '<select multiple name="test" class="selectfilter" '
            'data-field-name="test" data-is-stacked="0">\n</select>',
        )