Annotation filters

worf/filters.py

@@ -1,15 +1,53 @@
 from urllib.parse import urlencode
 
+from django.db.models.fields.related import ForeignObjectRel, RelatedField
 from django.http import QueryDict
 
 from url_filter.filtersets import ModelFilterSet
+from url_filter.exceptions import SkipFilter
 
 
-def generate_filterset(model):
+class AnnotatedModelFilterSet(ModelFilterSet):
+    def get_filters(self):
+        filters = super().get_filters()
+
+        if self.queryset is not None:
+            state = self._build_state()
+
+            for name in self.queryset.query.annotations.keys():
+                if name in self.Meta.exclude or name in filters:
+                    continue
+
+                try:
+                    annotation_filter = self._build_annotation_filter(name, state)
+                except SkipFilter:
+                    continue
+
+                if annotation_filter is not None:
+                    filters[name] = annotation_filter
+
+        return filters
+
+    def _build_annotation_filter(self, name, state):
+        field = self.queryset.query.annotations.get(name).output_field
+
+        if isinstance(field, RelatedField):
+            if not self.Meta.allow_related:
+                raise SkipFilter
+            return self._build_filterset_from_related_field(name, field)
+        elif isinstance(field, ForeignObjectRel):
+            if not self.Meta.allow_related_reverse:
+                raise SkipFilter
+            return self._build_filterset_from_reverse_field(name, field)
+
+        return self._build_filter_from_field(name, field)
+
+
+def generate_filterset(model, queryset):
     return type(
         f"{model.__name__}FilterSet",
-        (ModelFilterSet,),
-        dict(Meta=type("Meta", (), dict(model=model))),
+        (AnnotatedModelFilterSet,),
+        dict(Meta=type("Meta", (), dict(model=model, queryset=queryset))),
     )
 
 

worf/views/list.py

@@ -54,7 +54,7 @@ def __init__(self, *args, **kwargs):
 
         # generate a default filterset if a custom one was not provided
         if self.filter_set is None:
-            self.filter_set = generate_filterset(self.model)
+            self.filter_set = generate_filterset(self.model, self.queryset)
 
         # support deprecated search_fields and/or dict syntax (note that `and` does nothing)
         if isinstance(self.search_fields, dict):