packageVersion could be mandatory

[nevrome]

Package versions are essential for many parts of our infrastructure. Various code in trident and elsewhere could be simpler if this information was guaranteed to be there. This would be a breaking change, but working around that may be worth it.

[stschiff]

Yes, I think I'm with you on that!

I think as proposed by @TCLamnidis, there is an easy way to make this non-breaking, by simply setting unknown versions to 0.1.0 and spitting out a warning when reading such a package?

We could also think how to implement this in our Poseidon-Version check. Right now, we simply have a list of Poseidon-Versions supported by trident. If we follow the proposal above, we could extend that list towards old Poseidon-Versions, so that trident can read packages encoded with the older format. We could even come up with a smarter package-reading method, which makes versions mandatory for packages encoded in the new Poseidon-Version (refusing to read packages without version), but allowing old versions to be read by setting the default.