Merge pull request #9 from ployst/carles/serializer-builder

Add SerializerBuilder

drfutils/serializers.py

@@ -14,7 +14,15 @@ def get_querystring_fields(serializer, arg_name):
     return None
 
 
-class DynamicFieldsSerializerMixin(object):
+class FieldLimiterMixin(object):
+    def keep_only_fields(self, fields):
+        if fields is not None:
+            existing = set(self.fields.keys())
+            for field_name in existing - fields:
+                self.fields.pop(field_name)
+
+
+class DynamicFieldsSerializerMixin(FieldLimiterMixin):
     """
     Limit the number of fields to be retrieved as per request querystring.
 
@@ -35,11 +43,22 @@ def __init__(self, *args, **kwargs):
         """
         super().__init__(*args, **kwargs)
         fields = get_querystring_fields(self, 'fields')
+        self.keep_only_fields(fields)
 
-        if fields is not None:
-            existing = set(self.fields.keys())
-            for field_name in existing - fields:
-                self.fields.pop(field_name)
+
+class LimitedFieldsSerializerMixin(FieldLimiterMixin):
+    """
+    Limit the number of fields to be retrieved to Meta.only_fields
+
+    """
+    def __init__(self, *args, **kwargs):
+        """
+        Change the subset of fields to display based on only_fields
+
+        """
+        super().__init__(*args, **kwargs)
+        fields = set(self.Meta.only_fields)
+        self.keep_only_fields(fields)
 
 
 class ExpandableFieldsSerializerMixin(object):
@@ -68,3 +87,13 @@ def __init__(self, *args, **kwargs):
                     self.fields[field_name] = serializer_class(
                         context=self.context
                     )
+
+
+def SubSerializer(serializer_class, fields):
+    serializer_class = type(
+        'Sub{}'.format(serializer_class.__name__),
+        (LimitedFieldsSerializerMixin, serializer_class),
+        {}
+    )
+    serializer_class.Meta.only_fields = fields
+    return serializer_class

drfutils/tests/test_serializers.py

@@ -6,12 +6,17 @@
 from ..serializers import (
     DynamicFieldsSerializerMixin,
     ExpandableFieldsSerializerMixin,
+    SubSerializer,
 )
 
 
 class CreatorSerializer(serializers.Serializer):
     name = fields.CharField()
     other = serializers.SerializerMethodField()
+    nickname = fields.CharField()
+
+    class Meta:
+        fields = ('name', 'nickname', 'other')
 
     def get_other(self, *args):
         return 'field in expansion'
@@ -30,7 +35,7 @@ class TestExpandableFieldsSerializer(TestCase):
     def test_expands_requested_fields(self):
 
         class ThingWithCreator(object):
-            creator = {'name': '[email protected]'}
+            creator = {'name': '[email protected]', 'nickname': 'jim'}
 
         request = Mock()
         request.query_params.get.return_value = 'creator'
@@ -40,7 +45,11 @@ class ThingWithCreator(object):
 
         self.assertDictEqual(
             serializer.data['creator'],
-            {'name': '[email protected]', 'other': 'field in expansion'}
+            {
+                'name': '[email protected]',
+                'nickname': 'jim',
+                'other': 'field in expansion'
+            }
         )
 
     def test_does_not_expand_by_default(self):
@@ -105,3 +114,21 @@ class Thing(object):
         self.assertDictEqual(
             serializer.data, {'name': 'Jane', 'nickname': 'thesnake'}
         )
+
+
+class TestSerializerBuilder(TestCase):
+
+    def test_only_returns_requested_fields(self):
+        serializer_class = SubSerializer(CreatorSerializer, ('nickname',))
+        self.assertDictEqual(serializer_class.name, 'SubCreatorSerializer')
+
+    def test_only_returns_requested_fields(self):
+        class Thing(object):
+            name = 'Only James'
+            nickname = 'catnip'
+
+        jim = Thing()
+        serializer_class = SubSerializer(CreatorSerializer, ('nickname',))
+        serializer = serializer_class(jim)
+
+        self.assertDictEqual(serializer.data, {'nickname': 'catnip'})