Make querying over wagtail objects easier

opentech/apply/dashboard/tables.py

@@ -58,11 +58,35 @@ class Select2ModelMultipleChoiceFilter(Select2MultipleChoiceFilter, filters.Mode
     pass
 
 
+class WagtailMulitChoiceFilter(Select2ModelMultipleChoiceFilter):
+    @property
+    def wagtail_query(self):
+        # Queries on related pages will first attempt to query through the Page object
+        def is_page(relation):
+            return relation.field.related_model == Page
+
+        wagtail_path = list()
+        steps = self.field_name.split('__')
+        related_item = self.model
+        for step in steps:
+            related_item = getattr(related_item, step)
+            wagtail_path.append(step)
+            if is_page(related_item):
+                # Traverse over the page object to get the model at the other end
+                related_item = getattr(related_item.field.related_model, step).related.remote_field.model
+                wagtail_path.append(step)
+
+        return '__'.join(wagtail_path)
+
+    def get_filter_predicate(self, v):
+        return {self.wagtail_query: v}
+
+
 class SubmissionFilter(filters.FilterSet):
     round = Select2ModelMultipleChoiceFilter(queryset=get_used_rounds, label='Rounds')
     funds = Select2ModelMultipleChoiceFilter(name='page', queryset=get_used_funds, label='Funds')
     status = Select2MultipleChoiceFilter(name='status__contains', choices=status_options, label='Status')
-    lead = Select2ModelMultipleChoiceFilter(name='round__lead', queryset=get_round_leads, label='Lead')
+    lead = WagtailMulitChoiceFilter(name='round__lead', queryset=get_round_leads, label='Lead')
 
     class Meta:
         model = ApplicationSubmission