From 8f108e8bcf2d5cbef52fe70d522f1f03f293d649 Mon Sep 17 00:00:00 2001
From: Craig de Stigter <craig.destigter@koordinates.com>
Date: Wed, 6 Jan 2016 16:04:23 +1300
Subject: [PATCH] Fix nested validation error being rendered incorrectly.

Previously an extra list wrapped nested validation errors raised from serializer's validate() methods.
That was inconsistent with the format of validation errors raised by validate_<fieldname> methods.
i.e. these two resulted in *different* behaviour:

    def validate_foo(self):
        raise ValidationError(['bar'])

    def validate(self):
        raise ValidationError({'foo': ['bar']})
---
 rest_framework/serializers.py |  2 +-
 tests/test_validation.py      | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index e168abb25..3756aec01 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -314,7 +314,7 @@ def get_validation_error_detail(exc):
         # 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) else [value]
+            key: value if isinstance(value, (list, dict)) else [value]
             for key, value in exc.detail.items()
         }
     elif isinstance(exc.detail, list):
diff --git a/tests/test_validation.py b/tests/test_validation.py
index 855ff20e0..b6f274219 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -49,6 +49,24 @@ class ShouldValidateModelSerializer(serializers.ModelSerializer):
         fields = ('renamed',)
 
 
+class TestNestedValidationError(TestCase):
+    def test_nested_validation_error_detail(self):
+        """
+        Ensure nested validation error detail is rendered correctly.
+        """
+        e = serializers.ValidationError({
+            'nested': {
+                'field': ['error'],
+            }
+        })
+
+        self.assertEqual(serializers.get_validation_error_detail(e), {
+            'nested': {
+                'field': ['error'],
+            }
+        })
+
+
 class TestPreSaveValidationExclusionsSerializer(TestCase):
     def test_renamed_fields_are_model_validated(self):
         """