Use confine to check the existence of a command needed for the fact to resolve

[willaerk]

An initial puppet run (eg. in a vagrant box) will produce an error while trying to resolve the mongodb_version fact:

Facter: error while resolving custom fact "mongodb_version": undefined method '[]' for nil:NilClass

The reason is that the check for the existence of the mongo binary is inside the setcode block.

This pull request uses the fact confinement mechanism to pre-empt the fact resolution if the mongo binary is not available.

[ekohl]

I fail to see how this is different. It looks like which is working so something is on the system. This really looks like something that shouldn't work and shouldn't be done.

Have you checked why Facter::Core::Execution.which('mongo') returns something truthy but Facter::Core::Execution.execute('mongo --version 2>&1') returns something that doesn't match %r{MongoDB shell version:?\s+v?([\w\.]+)}?

Perhaps it should log a warning if that returns nil and not fail hard.

[ekohl]

https://puppet.com/docs/facter/3.11/custom_facts.html#confining-facts doesn't mention this form at all. I'm hesitant to rely on something that doesn't appear to be what it was intended to do.