representation exists

[andreineculau]

Thanks to @mootboy @kvakvs @sstrigler - a possible enhancement popped up today - the retrieve:missing callback checks if the resource is missing, but not if the representation is missing, which is what 404 is supposed to check against.

alternatives:

• leave it as today = leave the content type handler to decide whether to force a 404
• introduce a missing_representation callback; where? not sure

[mootboy]

In the basho webmachine style I'd say replace the atom definitions for outputting stuff and replace them with a representation_exists callback as the last node before 200 / 204 and now 404. But that's basho, dunno about hyper ;)

[andreineculau]

I have double-checked my diagram, and it is possible to check in the missing callback that either the entire resource or just the specific representation (decided in the Accept block) is missing or not.

I think the added documentation is enough to "fix" this.