What is the purpose of two seperate META files after building a distribution?

Question

When building a new distribution 2 meta files are generated. One uses the YAML format, and the other JSON. As far as I know, these are only used by other CPAN clients or other applications that want to have access to a meta file(for whatever reason). I'm trying to reason why an app would need access to both...

Are these two formats separately generated purely for convenience? i.e. Developer 1 prefers JSON therefore codes his apps to read the distribution META.json file while Developer 2 hates JSON and would rather reach for the YAML version?

Or is therefore some technical reason both would be needed by a single client/app that I'm overlooking?

Answer 1

The reason is that there have been two versions of the CPAN meta spec, with the more recent version specifying JSON instead of YAML. The YAML files are kept around in order to maintain compatibility with older tools that expect them, but any future metadata features will be added to the JSON version.

David Golden has some discussion of the change from YAML to JSON on his blog post announcing version 2 of the spec.