Handle empty body with json content-type as json

An empty request body should not imply HTML form semantics.

An attribute in a JSON object can either be:
 - not set at all,
 - null,
 - an empty list.

An HTML form isn't as flexible, so invariably turning an empty body into
a QueryDict makes it impossible to determine if a given value was passed
in as an empty list or if it was not set at all.

rest_framework/parsers.py

@@ -62,6 +62,9 @@ class JSONParser(BaseParser):
         parser_context = parser_context or {}
         encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
 
+        if not stream:
+            return {}
+
         try:
             data = stream.read().decode(encoding)
             return json.loads(data)

rest_framework/request.py

@@ -275,7 +275,7 @@ class Request(object):
         stream = self.stream
         media_type = self.content_type
 
-        if stream is None or media_type is None:
+        if stream is None and not media_type:
             empty_data = QueryDict('', encoding=self._request._encoding)
             empty_files = MultiValueDict()
             return (empty_data, empty_files)

tests/test_request.py

@@ -14,7 +14,7 @@ from django.utils import six
 
 from rest_framework import status
 from rest_framework.authentication import SessionAuthentication
-from rest_framework.parsers import BaseParser, FormParser, MultiPartParser
+from rest_framework.parsers import BaseParser, FormParser, JSONParser, MultiPartParser
 from rest_framework.request import Request
 from rest_framework.response import Response
 from rest_framework.test import APIClient, APIRequestFactory
@@ -51,6 +51,16 @@ class TestContentParsing(TestCase):
         request = Request(factory.head('/'))
         self.assertEqual(request.data, {})
 
+    def test_empty_body_yields_empty_dict_for_json_POST(self):
+        """
+        Ensure request.data returns empty dict for POST request with JSON
+        content type.
+        """
+        request = Request(factory.post('/', CONTENT_TYPE='application/json'))
+        request.parsers = (JSONParser(),)
+        self.assertEquals(type(request.data), dict)
+        self.assertEquals(request.data, {})
+
     def test_request_DATA_with_form_content(self):
         """
         Ensure request.data returns content for POST request with form content.