Refactor get_queryset_from_view

src/drf_yasg/inspectors/field.py

@@ -165,6 +165,25 @@ def get_model_field(model, field_name):
         return None
 
 
+def get_queryset_from_view(view, serializer=None):
+    """Try to get the queryset of the given view
+
+    :param view: the view instance or class
+    :param serializer: if given, will check that the view's get_serializer_class return matches this serialzier
+    :return: queryset or ``None``
+    """
+    try:
+        queryset = getattr(view, 'queryset', None)
+
+        if queryset is not None and serializer is not None:
+            # make sure the view is actually using *this* serializer
+            assert type(serializer) == view.get_serializer_class()
+
+        return queryset
+    except Exception:  # pragma: no cover
+        return None
+
+
 def get_parent_serializer(field):
     """Get the nearest parent ``Serializer`` instance for the given field.
 
@@ -231,21 +250,18 @@ class RelatedFieldInspector(FieldInspector):
             else:
                 # if the RelatedField has no queryset (e.g. read only), try to find the target model
                 # from the view queryset or ModelSerializer model, if present
-                view_queryset = getattr(self.view, 'queryset', None)
                 parent_serializer = get_parent_serializer(field)
-                if view_queryset is not None:
-                    # make sure the view is actually using *this* serializer
-                    try:
-                        if type(parent_serializer) != self.view.get_serializer_class():
-                            view_queryset = None
-                    except Exception as e:
-                        view_queryset = None
 
                 serializer_meta = getattr(parent_serializer, 'Meta', None)
-                this_model = getattr(serializer_meta, 'model', None) or getattr(view_queryset, 'model', None)
+                this_model = getattr(serializer_meta, 'model', None)
+                if not this_model:
+                    view_queryset = get_queryset_from_view(self.view, parent_serializer)
+                    this_model = getattr(view_queryset, 'model', None)
+
                 source = getattr(field, 'source', '') or field.field_name
                 if not source and isinstance(field.parent, serializers.ManyRelatedField):
                     source = field.parent.field_name
+
                 model = get_related_model(this_model, source)
                 model_field = get_model_field(model, target_field)