Fix detail_route and list_route overrides of serializer_class in schema generator

rest_framework/schemas.py

@@ -258,12 +258,22 @@ def get_serializer_fields(self, path, method, callback, view):
         if method not in ('PUT', 'PATCH', 'POST'):
             return []
 
-        if not hasattr(view, 'get_serializer_class'):
+        serializer_class = None
+
+        # looking for serializer_class override
+        if hasattr(callback, 'actions'):
+            func = getattr(view, callback.actions[method.lower()])
+            if 'serializer_class' in getattr(func, 'kwargs', ()):
+                serializer_class = func.kwargs['serializer_class']
+
+        if serializer_class is None and hasattr(view, 'get_serializer_class'):
+            serializer_class = view.get_serializer_class()
+
+        if serializer_class is None:
             return []
 
         fields = []
 
-        serializer_class = view.get_serializer_class()
         serializer = serializer_class()
 
         if isinstance(serializer, serializers.ListSerializer):

tests/test_schemas.py

@@ -5,6 +5,7 @@
 
 from rest_framework import filters, pagination, permissions, serializers
 from rest_framework.compat import coreapi
+from rest_framework.decorators import detail_route
 from rest_framework.response import Response
 from rest_framework.routers import DefaultRouter
 from rest_framework.schemas import SchemaGenerator
@@ -27,12 +28,21 @@ class ExampleSerializer(serializers.Serializer):
     b = serializers.CharField(required=False)
 
 
+class AnotherSerializer(serializers.Serializer):
+    c = serializers.CharField(required=True)
+    d = serializers.CharField(required=False)
+
+
 class ExampleViewSet(ModelViewSet):
     pagination_class = ExamplePagination
     permission_classes = [permissions.IsAuthenticatedOrReadOnly]
     filter_backends = [filters.OrderingFilter]
     serializer_class = ExampleSerializer
 
+    @detail_route(methods=['post'], serializer_class=AnotherSerializer)
+    def custom_action(self, request, pk):
+        return super(ExampleSerializer, self).retrieve(self, request)
+
 
 class ExampleView(APIView):
     permission_classes = [permissions.IsAuthenticatedOrReadOnly]
@@ -120,6 +130,16 @@ def test_authenticated_request(self):
                             coreapi.Field('pk', required=True, location='path')
                         ]
                     ),
+                    'custom_action': coreapi.Link(
+                        url='/example/{pk}/custom_action/',
+                        action='post',
+                        encoding='application/json',
+                        fields=[
+                            coreapi.Field('pk', required=True, location='path'),
+                            coreapi.Field('c', required=True, location='form'),
+                            coreapi.Field('d', required=False, location='form'),
+                        ]
+                    ),
                     'update': coreapi.Link(
                         url='/example/{pk}/',
                         action='put',