Fixed #27516 -- Made test client's response.json() cache the parsed JSON.

django/test/client.py

@@ -683,12 +683,14 @@ class Client(RequestFactory):
         self.cookies = SimpleCookie()
 
     def _parse_json(self, response, **extra):
+        if not hasattr(response, '_json'):
             if 'application/json' not in response.get('Content-Type'):
                 raise ValueError(
                     'Content-Type header is "{0}", not "application/json"'
                     .format(response.get('Content-Type'))
                 )
-        return json.loads(response.content.decode(), **extra)
+            response._json = json.loads(response.content.decode(), **extra)
+        return response._json
 
     def _handle_redirects(self, response, **extra):
         "Follows any redirects by requesting responses from the server using GET."

tests/test_client_regress/tests.py

@@ -1209,6 +1209,10 @@ class RequestMethodStringDataTests(SimpleTestCase):
         response = self.client.get('/json_response/')
         self.assertEqual(response.json(), {'key': 'value'})
 
+    def test_json_multiple_access(self):
+        response = self.client.get('/json_response/')
+        self.assertIs(response.json(), response.json())
+
     def test_json_wrong_header(self):
         response = self.client.get('/body/')
         msg = 'Content-Type header is "text/html; charset=utf-8", not "application/json"'