Add extra_attrs decorator for function-based view.

In this way, function-based view will have same behavior with
class view.

docs/api-guide/views.md

@@ -217,6 +217,21 @@ You may pass `None` in order to exclude the view from schema generation.
         return Response({"message": "Will not appear in schema!"})
 
 
+## View extra attrs decorator
+
+To set custom extra attribute on function-based view, you may use the `@extra_attrs` decorator.
+This must come *after* (below) the `@api_view` decorator. For example:
+
+    from rest_framework.decorators import api_view, extra_attrs
+
+    class ExtraClass:
+        pass
+
+    @api_view(['GET'])
+    @extra_attrs(extra_class=ExtraClass)
+    def view(request):
+        return Response({"message": "Hello for today! See you tomorrow!"})
+
 [cite]: https://reinout.vanrees.org/weblog/2011/08/24/class-based-views-usage.html
 [cite2]: http://www.boredomandlaziness.org/2012/05/djangos-cbvs-are-not-mistake-but.html
 [settings]: settings.md

rest_framework/decorators.py

@@ -72,6 +72,11 @@ def api_view(http_method_names=None):
 
         WrappedAPIView.schema = getattr(func, 'schema',
                                         APIView.schema)
+        for extra_attr in getattr(func, 'extra_attrs', []):
+            assert not (hasattr(WrappedAPIView, extra_attr)), \
+                '{} already has attribute {}'.format(func.__name__, extra_attr)
+            setattr(WrappedAPIView, extra_attr,
+                    getattr(func, extra_attr, None))
 
         return WrappedAPIView.as_view()
 
@@ -120,6 +125,15 @@ def schema(view_inspector):
     return decorator
 
 
+def extra_attrs(**kwargs):
+    def decorator(func):
+        func.extra_attrs = list(kwargs.keys())
+        for extra_attr, val in kwargs.items():
+            setattr(func, extra_attr, val)
+        return func
+    return decorator
+
+
 def action(methods=None, detail=None, url_path=None, url_name=None, **kwargs):
     """
     Mark a ViewSet method as a routable action.

tests/test_decorators.py

@@ -4,7 +4,7 @@ from django.test import TestCase
 from rest_framework import status
 from rest_framework.authentication import BasicAuthentication
 from rest_framework.decorators import (
-    action, api_view, authentication_classes, parser_classes,
+    action, api_view, authentication_classes, extra_attrs, parser_classes,
     permission_classes, renderer_classes, schema, throttle_classes
 )
 from rest_framework.parsers import JSONParser
@@ -166,6 +166,25 @@ class DecoratorTestCase(TestCase):
 
         assert isinstance(view.cls.schema, CustomSchema)
 
+    def test_extra_attrs(self):
+        """
+        Checks Custom extra attrs is set on view
+        """
+
+        def extra_func():
+            pass
+
+        class ExtraClass:
+            pass
+
+        @api_view(['get'])
+        @extra_attrs(extra_func=extra_func, extra_class=ExtraClass)
+        def view(request):
+            return Response({})
+
+        assert view.cls.extra_func is extra_func
+        assert view.cls.extra_class is ExtraClass
+
 
 class ActionDecoratorTestCase(TestCase):