Fixes #23447: Ignore ordering by a count field left out of the REST API response

netbox/netbox/api/filters.py

@@ -0,0 +1,29 @@
+from rest_framework import filters
+
+from netbox.api.fields import RelatedObjectCountField
+
+__all__ = (
+    'OrderingFilter',
+)
+
+
+class OrderingFilter(filters.OrderingFilter):
+    """
+    Extends DRF's OrderingFilter to accept a RelatedObjectCountField as an ordering key only when its annotation has
+    been applied to the queryset, which happens only when the field is included in the response.
+    """
+    def get_default_valid_fields(self, queryset, view, context=None):
+        valid_fields = super().get_default_valid_fields(queryset, view, context)
+        if hasattr(view, 'get_serializer_class'):
+            serializer_class = view.get_serializer_class()
+        else:
+            serializer_class = view.serializer_class
+        count_sources = {
+            field.source or field_name
+            for field_name, field in serializer_class._declared_fields.items()
+            if type(field) is RelatedObjectCountField
+        }
+        return [
+            (source, label) for source, label in valid_fields
+            if source not in count_sources or source in queryset.query.annotations
+        ]