Async REST API operations don't return 'Location' header

[Tony Espy]

Per the snapd REST API documentation on the wiki [1], when an async operation returns the status code 202, a 'Location' reply header should be provided that specifies the URL ( /v2/changes/{change-id-from-reply}) to be used to retrieve the operation's actual status.

This is being reported against snapd version 2.20, installed on a xenial desktop.

~$ sudo curl -D - -X POST -H "Content-Type: application/json" -d '{"action":"install"}' --unix-socket /run/snapd.socket 'http:/v2/snaps/tpm'
HTTP/1.1 202 Accepted
Content-Type: application/json
Date: Fri, 06 Jan 2017 18:36:05 GMT
Content-Length: 82

{"type":"async","status-code":202,"status":"Accepted","result":null,"change":"29"}

[1] https://github.com/snapcore/snapd/wiki/REST-API

[Robert Ancell (robert-ancell)]

Also note the "null" result that is returned. This seems like it should either be omitted or be {}.

[Michael Vogt (mvo)]

https://github.com/snapcore/snapd/pull/2690

[Gustavo Niemeyer (niemeyer)]

I suggest fixing the documentation instead of adding a Location header. We already provide the necessary data in the response. If the argument is avoiding parsing the response, that's not a great idea as it'll mean errors will also not be reported properly.