make document title / edit_url available through get_value_data

wagtail/documents/widgets.py

@@ -19,25 +19,34 @@ class AdminDocumentChooser(AdminChooser):
         super().__init__(**kwargs)
         self.document_model = get_document_model()
 
-    def render_html(self, name, value, attrs):
-        document, value = self.get_instance_and_id(self.document_model, value)
-        original_field_html = super().render_html(name, value, attrs)
+    def get_value_data(self, value):
+        if value is None:
+            return None
+        elif isinstance(value, self.document_model):
+            doc = value
+        else:  # assume document ID
+            doc = self.document_model.objects.get(pk=value)
 
-        # # Must import here because doing so at the top of the file is too early in the bootstrap.
-        # from wagtail.documents.permissions import permission_policy
-        # if not permission_policy.user_has_permission_for_instance(user, 'change', instance):
-        #     self.show_edit_link = False
+        return {
+            'id': doc.pk,
+            'title': doc.title,
+            'edit_url': reverse('wagtaildocs:edit', args=[doc.id]),
+        }
+
+    def render_html(self, name, value_data, attrs):
+        value_data = value_data or {}
+        original_field_html = super().render_html(name, value_data.get('id'), attrs)
 
         return render_to_string("wagtaildocs/widgets/document_chooser.html", {
             'widget': self,
             'original_field_html': original_field_html,
             'attrs': attrs,
-            'value': value,
-            'display_title': document.title if document else '',
-            'edit_url': reverse('wagtaildocs:edit', args=[document.id]) if document else '',
+            'value': bool(value_data),  # only used by chooser.html to identify blank values
+            'display_title': value_data.get('title', ''),
+            'edit_url': value_data.get('edit_url', ''),
         })
 
-    def render_js_init(self, id_, name, value):
+    def render_js_init(self, id_, name, value_data):
         return "createDocumentChooser({0});".format(json.dumps(id_))
 
     @property