Check for collection.Mapping instead of dict

issue #4901

rest_framework/serializers.py

@@ -15,7 +15,7 @@ from __future__ import unicode_literals
 import copy
 import inspect
 import traceback
-from collections import OrderedDict
+from collections import Mapping, OrderedDict
 
 from django.core.exceptions import ValidationError as DjangoValidationError
 from django.core.exceptions import ImproperlyConfigured
@@ -326,11 +326,11 @@ def as_serializer_error(exc):
     else:
         detail = exc.detail
 
-    if isinstance(detail, dict):
+    if isinstance(detail, Mapping):
         # If errors may be a dict we use the standard {key: list of values}.
         # Here we ensure that all the values are *lists* of errors.
         return {
-            key: value if isinstance(value, (list, dict)) else [value]
+            key: value if isinstance(value, (list, Mapping)) else [value]
             for key, value in detail.items()
         }
     elif isinstance(detail, list):
@@ -442,7 +442,7 @@ class Serializer(BaseSerializer):
         """
         Dict of native values <- Dict of primitive datatypes.
         """
-        if not isinstance(data, dict):
+        if not isinstance(data, Mapping):
             message = self.error_messages['invalid'].format(
                 datatype=type(data).__name__
             )

tests/test_serializer.py

@@ -4,9 +4,10 @@ from __future__ import unicode_literals
 import inspect
 import pickle
 import re
+import unittest
+from collections import Mapping
 
 import pytest
-
 from django.db import models
 
 from rest_framework import fields, relations, serializers
@@ -15,6 +16,11 @@ from rest_framework.fields import Field
 
 from .utils import MockObject
 
+try:
+    from collections import ChainMap
+except ImportError:
+    ChainMap = False
+
 
 # Test serializer fields imports.
 # -------------------------------
@@ -113,6 +119,31 @@ class TestSerializer:
         assert not serializer.is_valid()
         assert serializer.errors == {'non_field_errors': ['No data provided']}
 
+    @unittest.skipUnless(ChainMap, 'requires python 3.3')
+    def test_serialize_chainmap(self):
+        data = ChainMap({'char': 'abc'}, {'integer': 123})
+        serializer = self.Serializer(data=data)
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'char': 'abc', 'integer': 123}
+        assert serializer.errors == {}
+
+    def test_serialize_custom_mapping(self):
+        class SinglePurposeMapping(Mapping):
+            def __getitem__(self, key):
+                return 'abc' if key == 'char' else 123
+
+            def __iter__(self):
+                yield 'char'
+                yield 'integer'
+
+            def __len__(self):
+                return 2
+
+        serializer = self.Serializer(data=SinglePurposeMapping())
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'char': 'abc', 'integer': 123}
+        assert serializer.errors == {}
+
 
 class TestValidateMethod:
     def test_non_field_error_validate_method(self):