Drush fails to report error for bad alias within group

[AdamPS]

I recently discovered that my nightly backup had been silently failing for nearly a week. The backup runs from cron calling a custom drush command like this:
cronwrap drush -y @allbackup my-backup-command

I had mistakenly mistyped an alias in the group @allbackup. Drush printed a warning message and exited without running the command on any server yet with code 0. cronwrap deduced the command had succeeded so I didn't get any alert.

To reproduce the bug, set up aliases.drushrc.php as follows:
$aliases['myalias'] = ['site-list' => ['@badalias']];

Then run the sequence of shell commands below

$ drush @myalias status
You are about to execute 'status' non-interactively (--yes forced) on all of the following targets:
  @badalias
Continue?  (y/n): y
Not found: @badalias                         [warning]
$ echo $?
0

In contrast, drush correctly reports an error when running directly with a bad alias.

$ drush @badalias status
Could not find the alias @badalias                 [error]
$ echo $?
1

[greg-1-anderson]

It would indeed be preferable if Drush aborted with an error if any alias in a group did not exist.

[AdamPS]

@greg-1-anderson Thanks for the reply. I have raised PR #2854