fix(dynamic): add on_request_default_fields for DynamicAPIMixin

djb_utils/dynamic.py

 """
 Mixin to dynamically select only a subset of fields per DRF resource.
 """
+import logging
 import warnings
 from typing import Pattern, Dict, TypedDict, List
 
 from django.db.models import QuerySet
 from rest_framework.fields import empty
 
+logger = logging.getLogger(__name__)
+
 
 class OnRequestParams(TypedDict, total=False):
     related: List[str]
@@ -15,6 +18,7 @@ class OnRequestParams(TypedDict, total=False):
 
 class DynamicFieldsAPIViewMixin(object):
     on_request_fields: Dict[str, OnRequestParams] = {}
+    on_request_default_fields: List[str] = []
 
     def _process_related(self, related, field):
         if callable(related):
@@ -42,19 +46,26 @@ class DynamicFieldsAPIViewMixin(object):
         :return: list of related fields
         """
         related_fields = getattr(self, "on_request_fields", dict())
+        default_fields = ",".join(getattr(self, "on_request_default_fields",
+                                          list()))
         regex_fields = set(filter(lambda f: isinstance(f, Pattern),
                                   related_fields.keys()))
         out = list()
-        fields = self.request.query_params.get("fields", "").split(",")
+        fields = self.request.query_params \
+            .get("fields", default_fields) \
+            .split(",")
         for f in fields:
             out += self._process_related(
-                related_fields.get(f, dict()).get("related", list()), f)
+                related_fields.get(f, dict())
+                .get("related", list()), f)
             for rg in regex_fields:
                 if rg.match(f):
                     out += self._process_related(
-                        related_fields.get(rg, dict()).get("related", list()),
-                        f)
-        return list(set(out))
+                        related_fields.get(rg, dict())
+                        .get("related", list()), f)
+        related = list(set(out))
+        logger.debug("Related fields : %s", related)
+        return related
 
     def get_prefetch(self):
         """
@@ -69,34 +80,46 @@ class DynamicFieldsAPIViewMixin(object):
         """
 
         related_fields = getattr(self, "on_request_fields", dict())
+        default_fields = ",".join(getattr(self, "on_request_default_fields",
+                                          list()))
         regex_fields = set(filter(lambda f: isinstance(f, Pattern),
                                   related_fields.keys()))
         out = list()
-        fields = self.request.query_params.get("fields", "").split(",")
+        fields = self.request.query_params \
+            .get("fields", default_fields) \
+            .split(",")
         for f in fields:
             out += self._process_related(
-                related_fields.get(f, dict()).get("prefetch", list()), f)
+                related_fields.get(f, dict())
+                .get("prefetch", list()), f)
             for rg in regex_fields:
                 if rg.match(f):
                     out += self._process_related(
-                        related_fields.get(rg, dict()).get("prefetch", list()),
-                        f)
-        return list(set(out))
+                        related_fields.get(rg, dict())
+                        .get("prefetch", list()), f)
+        prefetch = list(set(out))
+        logger.debug("Prefetched fields : %s", prefetch)
+        return prefetch
 
     def get_annotations(self, qs: QuerySet):
         related_fields = getattr(self, "on_request_fields", dict())
+        default_fields = ",".join(getattr(self, "on_request_default_fields",
+                                          list()))
         regex_fields = set(filter(lambda f: isinstance(f, Pattern),
                                   related_fields.keys()))
         out = dict()
-        fields = self.request.query_params.get("fields", "").split(",")
+        fields = self.request.query_params \
+            .get("fields", default_fields) \
+            .split(",")
         for f in fields:
             out |= self._process_annotation(
-                related_fields.get(f, dict()).get("annotate", dict()), f)
+                related_fields.get(f, dict())
+                .get("annotate", dict()), f)
             for rg in regex_fields:
                 if rg.match(f):
                     out |= self._process_annotation(
-                        related_fields.get(rg, dict()).get("annotate", dict()),
-                        f)
+                        related_fields.get(rg, dict())
+                        .get("annotate", dict()), f)
         return qs.annotate(**out)