Comment 1 for bug 1763048

Just to be clear, at the time of writing all projects do the same check: they check that regexp, and that it neither starts nor ends with a dash, nor contains a double dash, nor is longer than 40 characters. The rationale for doing it like this instead of with a single regexp is well documented in the projects themselves; for example, from snapd:

// the full regexp we could use, "^(?:[a-z0-9]+-?)*[a-z](?:-?[a-z0-9])*$", is
// O(2ⁿ) on the length of the string in python. An equivalent regexp that
// doesn't have the nested quantifiers that trip up Python's re would be
// "^(?:[a-z0-9]|(?<=[a-z0-9])-)*[a-z](?:[a-z0-9]|-(?=[a-z0-9]))*$", but Go's
// regexp package doesn't support look-aheads nor look-behinds, so in order to
// have a unified implementation in the Go and Python bits of the project
// we're doing it this way instead. Check the length (if applicable), check
// this regexp, then check the dashes.