Hackers,
I noticed in testing and usage that pg_createsubscriber doesn't check for an existing replication slot before attempting to create one, whereas it *does* check for existing publications.
If it were to check for an existing replication slot, then the --dry-run mode would be able to detect the issue.
If this seems like a good feature, I'm happy to try and put together a patch for it.
Thanks,
Zane