As of version v[TBD], snapd will validate version strings in snaps.
For historically reasons snapd has been very lax about validation of the version string of snaps. However, the time seems right to make it consistent with what snapcraft and the review tools check. In doing this work we found that those two had diverging opinions on what constituted a valid version, so we’ve fixed this as well.
Here’s what’s a valid version, now (via the awesome regexper):
In case you’re curious, that’s