Cannot log in with more passwd entries with the same UID

I am not sure if it's a bug, however this works on the text console without problem since years.

Yes, that is ugly, I know: sometimes I need to test (while developing) softwares run as a specific unix user. To make this simple I often used the trick to add a line to /etc/passwd with different user name but the same numeric uid/gid as my account used to log in at lightdm's prompt. Usually I remove that line then, but I forgot it, and after reboot I couldn't log in.

According to /var/log/lightdm/lightdm.log lightdm treated as I want to use as this "phantom" user, which is not true. Using simple console login there is no such a problem.

AFAIK it's not so nice/legal to use /etc/passed entries refeering for the same unix numerical uid, so I am not sure if it's a bug which should be fixed, or it's something I shouldn't do, but as I've written above, it works (and always worked since 1995 on Debian/Ubuntu/Slackware/RedHat systems - as far as I can recall) on console logins at least.

By the way, I haven't added /etc/shadow entry for the user, only /etc/passwd. And of course I tried to log in with my "normal" user, not the "phantom".

thanks!

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: lightdm 1.4.0-0ubuntu2
ProcVersionSignature: Ubuntu 3.5.0-19.30-generic 3.5.7
Uname: Linux 3.5.0-19-generic i686
ApportVersion: 2.6.1-0ubuntu7
Architecture: i386
Date: Tue Dec 4 09:39:42 2012
InstallationDate: Installed on 2012-03-01 (277 days ago)
InstallationMedia: Ubuntu-Server 10.04.1 LTS "Lucid Lynx" - Release i386 (20100816.2)
MarkForUpload: True
SourcePackage: lightdm
UpgradeStatus: Upgraded to quantal on 2012-03-01 (277 days ago)