"404 row not found" when changing the display name of a AS ghost (SYN-572)

[matrixbot]

https://github.com/matrix-org/sytest/tree/markjh/ghost_displaynames/tests/60app-services/04displayname.pl

Steps:
AS doesn't register a ghost user
AS creates a room as a ghost user.
AS tries to change the display name of the ghost user.

HTTP/1.1 404 Not Found
Date: Mon, 04 Jan 2016 17:03:01 GMT
Server: Synapse/0.12.0 (b=develop,t=v0.12.0,f35f8d0)
 
{"errcode":"M_UNKNOWN","error":"No row found"}

(Imported from https://matrix.org/jira/browse/SYN-572)

(Reported by @NegativeMjark)

[matrixbot]

Jira watchers: @NegativeMjark

[richvdh]

keywords: /profile

[DMRobertson]

What is a "ghost user"?

[richvdh]

@Half-Shot this sounds like an AS term: any ideas?

[DMRobertson]

I would guess from this bit of perl
that "ghost" is oldspeak for "user in an application service's namespace". (User created with POST /v3/register with type "m.login.application_service" in the request body.)

[DMRobertson]

I tried to get the test linked in the description to run/fail again but ended up fighting sytest.

less /tmp/logs/results.tap 
  #** Use of uninitialized value $req in concatenation (.) or string at /sytest/run-tests.pl line 751.
  # $req = 
  #** Use of uninitialized value $req in exists at /sytest/run-tests.pl line 761.
  #** Use of uninitialized value $req in concatenation (.) or string at /sytest/run-tests.pl line 762.
  ok 1 AS-ghosted users can set their display name # skip lack of 
  1..1

AFAICS that means the test wasn't ran at all.

Given that we have a very similar-sounding test here which isn't in the test blacklist, I'm going to assume there's no problem here and move on.