Avoid creating empty suite directories when running suites that do not exist

[kinow]

Hi,

I executed cylc --debug --verbose --no-detach five, without registering the suite five. And I was expecting cylc to fail and nothing to be touched on my file system. However, looks like the ~/cylc-run/five (or wherever is cylc run/work directories specified) was still created, but empty.

This is a bit misleading. I noticed this happened after I moved my cylc run/work directories to /tmp, ran my suite five, minimized the terminal. Then from another terminal went to check the logs, and the directory was empty.

Took me a few seconds to understand why that happened. The issue happens with 7.8.x line too, and that's because before checking if the suite exists, we try to create auth files (create_auth_files call). I think this logic should be changed, and instead the auth files should be created only if the suite exists.

https://github.com/cylc/cylc/blob/d2e649bfcdaf655a0ae56bf128f213a57e4e612c/lib/cylc/scheduler_cli.py#L94-L104

Cheers
Bruno

[kinow]

Not sure if we need to worry about 7.8.x for this small one. Probably?

[hjoliver]

I can't look at the code right now, but this might be complicated slightly by auto-registration of a suite in $PWD by cylc run. (Should still be able to check if there is a suite in $PWD though, before creating auth files).

[hjoliver]

Not sure if we need to worry about 7.8.x for this small one. Probably?

Yes, better do both branches.