I’m using Wagtail’s ChooserViewSet to display a widget in the admin form. The widget uses an external API to get available questions. I want to filter these questions by passing a parameter dataset_id to the queryish model.

To do that, I’ve been following Wagtail’s documentation on linked_fields (https://docs.wagtail.org/en/stable/extending/generic_views.html#limiting-choices-via-linked-fields). The problem is, that the field is inside a streamfield. Sample code snippet below:

class MyPage(Page):
    content = StreamField(
        [
            ('questions', QuestionBlock())
        ],
        verbose_name=_('Content'),
        blank=True,
        use_json_field=True,
    )
    content_panels = (
        Page.content_panels
        + [
            FieldPanel('content', classname='collapsible')
        ]
    )
    
class QuestionBlock(StructBlock):
    dataset_id = CharBlock()
    questions = ChoiceBlock(
        widget=QuestionChooserWidget(
            linked_fields={
                'dataset_id': {'match': r'???????????', 'append': 'dataset_id'}
            }
        )
    )


class QuestionChooserViewSet(ChooserViewSet):
    model = Question

    choose_one_text = 'Choose a question.'
    choose_another_text = 'Choose another question.'

    url_filter_parameters = ["dataset_id"]
    preserve_url_parameters = ["multiple", "dataset_id"]


QuestionChooserViewSet = QuestionChooserViewSet('question_chooser')
QuestionChooserWidget = QuestionChooserViewSet.widget_class

Do you know how I can construct a proper regex to get this dataset_id?

In the Wagtail docs it’s slightly mentioned but doesn’t elaborate on it in any way. (https://docs.wagtail.org/en/stable/extending/generic_views.html#limiting-choices-via-linked-fields)

PersonChooserWidget(linked_fields={
    'country': {'selector': '#id_country'}  # equivalent to 'country': '#id_country'
})

# Look up by ID
PersonChooserWidget(linked_fields={
    'country': {'id': 'id_country'}
})

# Regexp match, for use in StreamFields and InlinePanels where IDs are dynamic:
# 1) Match the ID of the current widget's form element (the PersonChooserWidget)
#      against the regexp '^id_blog_person_relationship-d+-'
# 2) Append 'country' to the matched substring
# 3) Retrieve the input field with that ID
PersonChooserWidget(linked_fields={
    'country': {'match': r'^id_blog_person_relationship-d+-', 'append': 'country'},
})

Is there any specific logic to construct this **r’^id_blog_person_relationship-d+-‘ **thing???