Added three options to ModelSerializer: meta_fields, meta_exclude and meta_preset

rest_framework/serializers.py

@@ -901,6 +901,136 @@ class ModelSerializer(Serializer):
     # "HTTP 201 Created" responses.
     url_field_name = None
 
+    def __init__(self, *args, **kwargs):
+        kwargs.pop('meta_fields', None)
+        kwargs.pop('meta_exclude', None)
+        kwargs.pop('meta_preset', None)
+        super(ModelSerializer, self).__init__(*args, **kwargs)
+
+    def __new__(cls, *args, **kwargs):
+        if 'meta_fields' in kwargs:
+            fields = kwargs.pop('meta_fields')
+            if fields == '__all__':
+                fields = []
+            return cls.meta_fields(*fields)(*args, **kwargs)
+        if 'meta_exclude' in kwargs:
+            return cls.meta_exclude(*kwargs.pop('meta_exclude'))(*args, **kwargs)
+        if 'meta_preset' in kwargs:
+            return cls.meta_preset(kwargs.pop('meta_preset'))(*args, **kwargs)
+        return super(ModelSerializer, cls).__new__(cls, *args, **kwargs)
+
+    @classmethod
+    def meta_fields(cls, *fields):
+        """
+        Create new class based on the current with overrode Meta parameters.
+        Option `exclude` of base serializer is going to None.
+
+        Example of usage in serializers:
+        class UserSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = User
+
+        class ItemSerializer(serializers.ModelSerializer):
+            user = UserSerializer(meta_fields=['id', 'name'])
+
+            class Meta:
+                model = Item
+
+        Example of usage in views:
+        class UserViewSet(viewsets.ModelViewSet):
+            serializer_class = UserSerializer.meta_fields('id', 'name', 'expiration_date')
+        """
+        if not len(fields):
+            fields = '__all__'
+        meta = getattr(cls, 'Meta', type('Meta', (), {}))
+        return type(cls.__name__, (cls,), {
+            'Meta': type('Meta', (meta,), {
+                'fields': fields,
+                'exclude': None
+            })
+        })
+
+    @classmethod
+    def meta_exclude(cls, *exclude):
+        """
+        Create new class based on the current with overrode Meta parameters.
+        If base serializer has meta option `fields`, fields will exclude from its.
+
+        Example of usage in serializers:
+        class UserSerializer(serializers.ModelSerializer):
+            products = ProductsSerializer(many=True)
+
+            class Meta:
+                model = User
+
+        class ItemSerializer(serializers.ModelSerializer):
+            user = UserSerializer(meta_exclude=['products'])
+
+            class Meta:
+                model = Item
+
+        Example of usage in views:
+        class UserViewSet(viewsets.ModelViewSet):
+            serializer_class = UserSerializer.meta_exclude('products')
+        """
+        meta = getattr(cls, 'Meta', type('Meta', (), {}))
+        meta_fields = getattr(meta, 'fields', None)
+        exclude_props = []
+        if isinstance(meta_fields, list) or isinstance(meta_fields, tuple):
+            meta_fields = [field_ for field_ in meta_fields if field_ not in exclude]
+            exclude = None
+        else:
+            meta_fields = None
+            exclude_props = [key for key, prop in cls._declared_fields.items() if isinstance(prop, Field)]
+            exclude = list(filter(lambda f: f not in exclude_props, exclude))
+        return type(cls.__name__, (cls,), {
+            'Meta': type('Meta', (meta,), {
+                'fields': meta_fields,
+                'exclude': exclude
+            }),
+            **{field: None for field in exclude_props}
+        })
+
+    @classmethod
+    def meta_preset(cls, name):
+        """
+        Create new class based on the current with overrode Meta parameters.
+        It will check meta option `presets` and try to get it by name.
+        Presets - prepared some schemes, which simplify manipulating with meta option.
+
+        Example of usage in serializers:
+        class UserSerializer(serializers.ModelSerializer):
+            products = ProductsSerializer(many=True)
+
+            class Meta:
+                model = User
+                presets = {
+                    'short': {
+                        'fields': ['id', 'name']
+                    },
+                    'light': {
+                        'exclude': ['products']
+                    }
+                }
+
+        class ItemSerializer(serializers.ModelSerializer):
+            user = UserSerializer(meta_preset='short')
+
+            class Meta:
+                model = Item
+
+        Example of usage in views:
+        class UserViewSet(viewsets.ModelViewSet):
+            serializer_class = UserSerializer.meta_preset('light')
+        """
+        meta = getattr(cls, 'Meta', type('Meta', (), {}))
+        presets = getattr(meta, 'presets', {})
+        preset = presets.get(name, None)
+        assert preset is not None, ('Preset of `%s` with `%s` name doesn\'t exist.' % (cls.__name__, name))
+        return type(cls.__name__, (cls,), {
+            'Meta': type('Meta', (meta,), preset)
+        })
+
     # Default `create` and `update` behavior...
     def create(self, validated_data):
         """