Cleaner content negotiation. Occurs after permissions. Optional 'force' flag.

1 files changed, 32 insertions, 3 deletions

diff --git a/djangorestframework/contentnegotiation.py b/djangorestframework/contentnegotiation.py
index 223919ef..1c646ca7 100644
--- a/djangorestframework/contentnegotiation.py
+++ b/djangorestframework/contentnegotiation.py
@@ -1,24 +1,40 @@
 from djangorestframework import exceptions
 from djangorestframework.settings import api_settings
 from djangorestframework.utils.mediatypes import order_by_precedence
+from django.http import Http404
 import re
 
 MSIE_USER_AGENT_REGEX = re.compile(r'^Mozilla/[0-9]+\.[0-9]+ \([^)]*; MSIE [0-9]+\.[0-9]+[a-z]?;[^)]*\)(?!.* Opera )')
 
 
 class BaseContentNegotiation(object):
-    def determine_renderer(self, request, renderers):
-        raise NotImplementedError('.determine_renderer() must be implemented')
+    def negotiate(self, request, renderers, format=None, force=False):
+        raise NotImplementedError('.negotiate() must be implemented')
 
 
 class DefaultContentNegotiation(object):
     settings = api_settings
 
-    def negotiate(self, request, renderers):
+    def negotiate(self, request, renderers, format=None, force=False):
         """
         Given a request and a list of renderers, return a two-tuple of:
         (renderer, media type).
+
+        If force is set, then suppress exceptions, and forcibly return a
+        fallback renderer and media_type.
+        """
+        try:
+            return self._negotiate(request, renderers, format)
+        except (Http404, exceptions.NotAcceptable):
+            if force:
+                return (renderers[0], renderers[0].media_type)
+            raise
+
+    def _negotiate(self, request, renderers, format=None):
+        """
+        Actual implementation of negotiate, inside the 'force' wrapper.
         """
+        renderers = self.filter_renderers(renderers, format)
         accepts = self.get_accept_list(request)
 
         # Check the acceptable media types against each renderer,
@@ -33,6 +49,19 @@ class DefaultContentNegotiation(object):
 
         raise exceptions.NotAcceptable(available_renderers=renderers)
 
+    def filter_renderers(self, renderers, format):
+        """
+        If there is a '.json' style format suffix, only use
+        renderers that accept that format.
+        """
+        if not format:
+            return renderers
+
+        renderers = [renderer for renderer in renderers
+                     if renderer.can_handle_format(format)]
+        if not renderers:
+            raise Http404()
+
     def get_accept_list(self, request):
         """
         Given the incoming request, return a tokenised list of