"version: 0.2" returns confusing error message (trunk)

[Gerry Boland]

I'm using snapcraft trunk. Since https://github.com/snapcore/snapcraft/pull/2334 landed, my old snapcraft files cause this error:

Issues while validating snapcraft.yaml: The 'version' property does not match the required schema: 2.11 is not a valid snap version string. Snap versions consist of upper- and lower-case alphanumeric characters, as well as periods, colons, plus signs, tildes, and hyphens. They cannot begin with a period, colon, plus sign, tilde, or hyphen. They cannot end with a period, colon, or hyphen.

The message appears contradictory, as "2.11" does fulfil the requirements mentioned.

It was non-obvious to figure out that

  version: 2.11

is incorrect, but

  version: "2.11"

is considered correct.

If I stumble on this, many others will, as lot of existing docs refer to the non-quoted style:

https://github.com/ubuntu-core/snapcraft-examples/blob/master/05-hello-world-combined/snapcraft.yaml
https://docs.snapcraft.io/snapcraft-yaml-reference/4276

Can the old non-quoted style be made acceptable again? Just to keep backward compatibility?

At the very least, can you make the error message more suitable?

[Gerry Boland (gerboland)]

Note, I was testing snapcraft against older yaml files I'd made which worked before. I did not add a "base" specifier or anything