false negative for readonly fields

[tumb1er]

We have "all fields" form with one field marked as "required" and "readonly_fields" hiding some of them on changeform admin page.

class SeasonForm(ModelForm):
    class Meta:
        model = models.Season
        fields = '__all__'

    parent = ModelChoiceField(queryset=..., required=True)

class SeasonAdmin(ModelAdmin):
    form = SeasonForm
    readonly_fields = ('parent',)

Pressing "save" on an existing valid object we got "invisible" error:

That's because "parent" field is still required and readonly at the same time.
So, django renders it without any form input and no value is passed in POST request.

But, we can't reproduce it with django-admin-smoke-based tests, because "readonly_fields" are not taken into account.

Below is a fix that makes our error reproducible:

def get_form_data_from_response(self, r: HttpResponseBase
                                    ) -> dict[str, Any]:
        data = super().get_form_data_from_response(r)
        cd = getattr(r, 'context_data')
        readonly_modeladmin_fields = cd['adminform'].readonly_fields
        for f in readonly_modeladmin_fields:
            data.pop(f, None)
        return data