support aliases in hiera yaml

[akerl]

This enables support for Hiera YAML files that contain aliases. As an example, with the current version I see this error:

❯ bundle exec rake syntax
---> syntax:manifests
---> syntax:templates
---> syntax:hiera:yaml
ERROR: Failed to parse data/mac/2c:4d:54:4f:be:c3.yaml: Alias parsing was not enabled. To enable it, pass `aliases: true` to `Psych::load` or `Psych::safe_load`.

This is the file it's referring to: https://github.com/halyard/halyard/blob/main/data/mac/2c%3A4d%3A54%3A4f%3Abe%3Ac3.yaml#L43

This PR adds the aliases: true flag, which seems right to me given that Puppet/Hiera allow aliases when parsing YAML.

[ekohl]

Looks like you need to do some version detection if the aliases keyword is supported.

[akerl]

Good catch. I think I've fixed it. 2 remaining failures seem to be expected, since the latest Puppet doesn't work w/ older Ruby versions.

[bastelfreak]

Hi, please rebase after #145 got merged

[akerl]

Updated!

[ekohl]

Should this look at Psych::VERSION instead?

[akerl]

It felt more hacky to pin to an internal library version vs the more top-level Ruby version

[ekohl]

Can't you update Psych via dependencies? Either way this is still pretty hacky and it's not going to get cleaner so I'm fine either way. I guess it's fine either way.

[ekohl]

And as I press submit, perhaps the yamlargs should be defined outside of the filelist.each loop. I really hope it's not going to change in between runs.

[bastelfreak]

I agree with @ekohl here. Ruby bundles a Psych version, but it can be updated. So we should check for the Psych version, not the Ruby version.

[akerl]

Updated to be outside the loop and use Psych::VERSION

[ekohl]

Thanks!