JsonResponse loses encoding support in Content-Type header

[Curtis Maloney]

By default when a content_type is not passed to HttpResponse it will create one from settings.DEFAULT_CONTENT_TYPE, and attach the encoding.

So, when unspecified, the header will appear as:

Content-Type: text/html; encoding=utf-8

However, if you specify the content_type, this action is not taken.

That's understandable in a "consenting adults" context, however the JsonResponse sets content_type using kwargs.setdefault, thus forcing the loss of encoding annotation in all responses.

I propose instead that HttpResponseBase check for a default_content_type property to override settings.DEFAULT_CONTENT_TYPE, thus:

django/http/response.py

@@ -54 +54 @@
         self._reason_phrase = reason
         self._charset = charset
         if content_type is None:
-            content_type = '%s; charset=%s' % (settings.DEFAULT_CONTENT_TYPE,
-                                               self.charset)
+            content_type = getattr(self, 'default_content_type', settings.DEFAULT_CONTENT_TYPE)
+            content_type = '%s; charset=%s' % (content_type, self.charset)
         self['Content-Type'] = content_type

[Curtis Maloney]

Oops, forgot the second part of the patch:

@@ -470,11 +470,11 @@ class JsonResponse(HttpResponse):
     :param safe: Controls if only ``dict`` objects may be serialized. Defaults
       to ``True``.
     """
+    default_content_type = 'application/json'
 
     def __init__(self, data, encoder=DjangoJSONEncoder, safe=True, **kwargs):
         if safe and not isinstance(data, dict):
             raise TypeError('In order to allow non-dict objects to be '
                 'serialized set the safe parameter to False')
-        kwargs.setdefault('content_type', 'application/json')
         data = json.dumps(data, cls=encoder)
         super(JsonResponse, self).__init__(content=data, **kwargs)

[Tim Graham]

Including a charset on application/json responses is invalid according to #23949.

[Claude Paroz]

Isn't this one a simple duplicate of #23949?

[Tim Graham]

I think so, but I thought I'd give Curtis an opportunity to say if there are any other valid use cases this patch might enable.

[Curtis Maloney]

The reading is quite clear, so I guess the bug I was encountering which inspired this must be further down the line -- possibly in requests.