Let developer specify a root page for a PageChooserPanel

[shezi]

We have a situation where a client has a deep page structure with several similar departments, each with similar sub-pages. They want to make linking of specific sub-pages to the "department index" easier with a page chooser. That page chooser should be anchored to the current page and only show sub-pages of that page (still of a certain type).

It would be nice if we could specify the root page of a PageChooserPanel and set it to the current page dynamically.

[shezi]

Related, but not the same: #670 and #2756 and #1250

[an-ant0ni0]

We encounter the very same issue.
I found so far a hacky javascript solution which is not working anymore: https://stackoverflow.com/a/65441715

Another possibility is to use the on_instance_bound hook (https://stackoverflow.com/a/59905949):

class InstanceAwareStreamFieldPanel(StreamFieldPanel):
    def on_instance_bound(self):
        if not self.form:
            return
        widget = self.form[self.field_name].field.widget

        for _, child_block in widget.block_def.child_blocks.items():
            self.recursive(child_block)

    def recursive(self, block):
        if hasattr(block, "widget") and isinstance(block.widget, AdminChildPageChooser):
            block.widget = AdminChildPageChooser(
                target_models=block.widget.target_models,
                can_choose_root=block.widget.can_choose_root,
                page_instance_id=self.instance.id,
            )

        if hasattr(block, "child_block"):
            self.recursive(block.child_block)

        if not hasattr(block, "child_blocks"):
            return
        for _, child_block in block.child_blocks.items():
            self.recursive(child_block)

Then extending the AdminPageChooser and the PageChooserBlock to render a different template:

class AdminChildPageChooser(AdminPageChooser):
    def __init__(self, **kwargs):
        self.page_instance_id = kwargs.pop("page_instance_id", None)
        super().__init__(**kwargs)

    def render_html(self, name, value_data, attrs):
        value_data = value_data or {}

        return render_to_string(
            "wagtailadmin/child_page_chooser.html",
            {
                "widget": self,
                "original_field_html": "",
                "attrs": attrs,
                "value": bool(
                    value_data
                ),  # only used by chooser.html to identify blank values
                "display_title": value_data.get("display_title", ""),
                "edit_url": value_data.get("edit_url", ""),
                "page_instance_id": self.page_instance_id,
            },
        )


class ChildPageChooserBlock(blocks.PageChooserBlock):
    def __init__(
        self,
        page_type=None,
        can_choose_root=False,
        target_model=None,
        **kwargs,
    ):
        self.page_instance_id = kwargs.pop("page_instance_id", None)

        super().__init__(
            page_type=page_type,
            can_choose_root=can_choose_root,
            target_model=target_model,
            **kwargs,
        )

    @cached_property
    def widget(self):
        return AdminChildPageChooser(
            target_models=self.target_models,
            can_choose_root=self.can_choose_root,
            page_instance_id=self.page_instance_id,
        )

child_page_chooser.html:

{% extends "wagtailadmin/widgets/chooser.html" %}
{% load wagtailadmin_tags %}

{% block unchosen_icon %}{% icon name="doc-empty-inverse" %}{% endblock unchosen_icon %}
{% block chosen_icon %}{% icon name="doc-empty-inverse" %}{% endblock chosen_icon %}
{% block chooser_attributes %}
  {% if page_instance_id %}
    data-chooser-url="{% url 'wagtailadmin_choose_page_child' page_instance_id %}"
  {% else %}
    data-chooser-url="{% url 'wagtailadmin_choose_page' %}"
  {% endif %}
{% endblock %}

The rendered html will be cached, so it only works for the first time.
Also the iteration to find the correct widgets to replace in the on_instance_bound hook and the code duplication is quite nasty.

Long story short: We would really appreciate a clean api to set the root page for the PageChooser.

[an-ant0ni0]

We found a solution for our needs with https://github.com/wagtail/wagtail-generic-chooser.
Not sure, why we do not found this excellent toolkit earlier.