Raise a rescuable exception when Rails doesn't know what to do with the format, rather than responding with a head :not_acceptable (406)

3 files changed, 5 insertions, 2 deletions

diff --git a/actionpack/lib/action_controller/metal/exceptions.rb b/actionpack/lib/action_controller/metal/exceptions.rb
index 9a9db0fe5f..90648c37ad 100644
--- a/actionpack/lib/action_controller/metal/exceptions.rb
+++ b/actionpack/lib/action_controller/metal/exceptions.rb
@@ -38,4 +38,7 @@ module ActionController
 
   class UnknownHttpMethod < ActionControllerError #:nodoc:
   end
+  
+  class UnknownFormat < ActionControllerError #:nodoc:
+  end
 end
diff --git a/actionpack/lib/action_controller/metal/mime_responds.rb b/actionpack/lib/action_controller/metal/mime_responds.rb
index f467b74256..2c96145820 100644
--- a/actionpack/lib/action_controller/metal/mime_responds.rb
+++ b/actionpack/lib/action_controller/metal/mime_responds.rb
@@ -375,8 +375,7 @@ module ActionController #:nodoc:
         lookup_context.rendered_format = lookup_context.formats.first
         collector
       else
-        head :not_acceptable
-        nil
+        raise ActionController::UnknownFormat.new
       end
     end
 
diff --git a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
index c0532c80c4..982f6641bf 100644
--- a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
+++ b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
@@ -10,6 +10,7 @@ module ActionDispatch
       'AbstractController::ActionNotFound'         => :not_found,
       'ActionController::MethodNotAllowed'         => :method_not_allowed,
       'ActionController::NotImplemented'           => :not_implemented,
+      'ActionController::UnknownFormat'            => :not_acceptable,
       'ActionController::InvalidAuthenticityToken' => :unprocessable_entity
     )