Item6909: TWiki::Attach::_expandAttrs() yields incorrect value for 'USER' when you use a custom user mapping handler

TWiki::Attach::_expandAttrs() has the following lines:

    elsif ( $attr eq 'USER' ) {
        my $user = $info->{user} || 'UnknownUser';
        my $cUID;
        if( $user ) {
            $cUID = $users->getCanonicalUserID( $user );
            if (!$cUID) {
                # Not a login name or a wiki name. Is it a valid cUID?
                my $ln = $users->getLoginName($user);
                $cUID = $user if defined $ln && $ln ne 'unknown';
            }
        }

This is not right because TWiki::Users::getCanonicalUserID($user) assumes $user is not a cUID while $user may. If a cUID and the corresponding login name are different, it's not possible for the user mapping handler to have TWiki::Users::getCanonicalUserID($user) return $user.

You need to first assume $user is a cUID and then resort to wiki name. In the spirit of this, TWiki::Render::renderRevisionInfo() has the following lines.

   my $cUID = $users->getLoginName($user) ?
       $user : $users->getCanonicalUserID( $user );

This does not consider the possibility of 'unknown' login name. So the above should be:

        my $ln = $users->getLoginName($user);
        my $cUID = defined($ln) && $ln ne 'unknown' ?
            $user : $users->getCanonicalUserID( $user );

This needs to be applied to TWiki::Attach::_expandAttrs().

-- TWiki:Main/HideyoImazu - 2012-07-31