more improvements for tag serializer

utils/tag_serializers.py

@@ -5,7 +5,7 @@ from rest_framework.fields import CharField, ListField
 from rest_framework.serializers import raise_errors_on_nested_writes
 from rest_framework.utils import model_meta
 
-from tagulous.models.descriptors import FakeTagRelatedManager
+from tagulous.models.managers import TagRelatedManagerMixin
 
 from taggit_serializer.serializers import TagListSerializerField, TaggitSerializer
 
@@ -100,8 +100,7 @@ class CustomTagSerializer(serializers.ModelSerializer):
         if many_to_many:
             for field_name, value in many_to_many.items():
                 field = getattr(instance, field_name)
-                import ipdb; ipdb.set_trace()
-                if type(field) == "<class 'tagulous.models.descriptors.TagRelatedManager'>":
+                if field_name in ('tags', 'category', 'attributes'):
                     for item in value:
                         field.set(item)
                 else:
@@ -112,10 +111,34 @@ class CustomTagSerializer(serializers.ModelSerializer):
     def update(self, instance, validated_data):
         to_be_tagged, validated_data = self._pop_tags(validated_data)
 
-        tag_object = super(CustomTagSerializer, self).update(
-            instance, validated_data)
+        raise_errors_on_nested_writes('update', self, validated_data)
+        info = model_meta.get_field_info(instance)
 
-        return self._save_tags(tag_object, to_be_tagged)
+        # Simply set each attribute on the instance, and then save it.
+        # Note that unlike `.create()` we don't need to treat many-to-many
+        # relationships as being a special case. During updates we already
+        # have an instance pk for the relationships to be associated with.
+        m2m_fields = []
+        for attr, value in validated_data.items():
+            if attr in info.relations and info.relations[attr].to_many:
+                m2m_fields.append((attr, value))
+            else:
+                setattr(instance, attr, value)
+
+        instance.save()
+
+        # Note that many-to-many fields are set after updating instance.
+        # Setting m2m fields triggers signals which could potentially change
+        # updated instance and we do not want it to collide with .update()
+        for attr, value in m2m_fields:
+            field = getattr(instance, attr)
+            if attr in ('tags', 'category', 'attributes'):
+                for item in value:
+                    field.set(item)
+            else:
+                field.set(value)
+
+        return self._save_tags(instance, to_be_tagged)
 
     def _save_tags(self, tag_object, tags):
         for key in tags.keys():