Unlink via ssh doesn't show --dry-run command

[srchulo]

When I run a script with --dry-run that calls unlink via ssh, it does not show the unlink command in the --dry-run:

my $doit = Doit->init;
{       
    my $ssh = $doit->do_ssh_connect('host');
    $ssh->system('/bin/touch', '/home/user/hi');
    $ssh->unlink('/home/user/hi');
}   

perl hi.pl --dry-run
INFO: /bin/touch /home/user/hi (dry-run)

But when I actually run it, it does run the unlink and it logs it out:

perl hi.pl 
INFO: /bin/touch /home/user/hi
INFO: unlink /home/user/hi

[eserte]

The unlink command only logs something if it would actually do something. However, in your example the file to be deleted was only created with a dry-run command itself, so it did not exist for the unlink command.

This problem is broader. For example dry-run would even fail if one touches a file and then runs the change_file command — because change_file requires an existing file. I was thinking about keeping track what would happen to the file system in a dry-run mode, e.g. files created, files deleted, content to files written... some kind of a virtual in-memory file system. If the user would then use one of the Doit commands for touching a file (touch or create_file_if_nonexisting), then unlink could first lookup into this virtual file system. However, this would not work if the user uses run or system --- in this case probably the user should give Doit a hint that the system commands creates something in the file system, similar to Puppet's creates option in its exec resource.

[srchulo]

Ah, I see. I guess I misunderstood --dry-run mode. I expected it to log what it would attempt to do, not what it would actually do, since that could be different at runtime, based on the other doit commands, as you noted. It could also be different based on other perl code run locally in the same script not via Doit, so I think it would be very hard to predict if it would have an effect or not. I expected unlink to run and have have no effect if the file did not exist.

I think a hint like you mentioned above may be best, since as you pointed out, run or system could really do anything.

[srchulo]

And I guess this probably also applies to things like cond_run as well. I guess even though it's really hard to know what will happen since we are not actually running commands, showing everything may not be the best either, since there is branching and only some things may actually be run.

I do think branching is slightly different from things that could be attempted and aren't conditional. For instance, unlink I think it would be clear that if it was shown, I wouldn't expect it to do anything if the file didn't exist. But for cond_run or if/else branching, that would be really complicated.