Make hyphen optional for prerelease suffix

[jtcohen6]

resolves #129

Not sure how to test this! It's been a little while since I did anything in this repo :)

[dbeatty10]

I'm going to work on #131 (and #132) so that we can try to add some tests here before merging.

[dbeatty10]

Testing framework

#133 adds some simple regex tests and instructions for running them. Currently, they are crafted strictly towards SemVer 2.0, so the unit tests would need to be adjusted slightly to accommodate an optional hyphen for prerelease suffix.

Can we have it all?

Is there any way we could achieve consistency between Hubcap + db-core and have strict SemVer for dbt packages and follow PEP 440 version strings for dbt adapters?

Converting versions between PyPI and semver provides some useful commentary and code. You can see how the semver project's git tags compare to their PyPI releases:

git tag	PyPI release
3.0.0-dev.3	3.0.0.dev3
3.0.0-dev.2	3.0.0.dev2
3.0.0-dev.1	3.0.0.dev1
2.13.0	2.13.0
2.12.0	2.12.0
2.11.0	2.11.0

[joellabes]

Does this regex now slightly deviate from the official site? Or had it moved forward and we hadn't moved with it?

[dbeatty10]

The regex in the main branch currently matches the "named groups" regular expression in SemVer 2.0.0 precisely:
^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$

That regex has not changed (and probably will not change within SemVer 2.x).

This PR just adds a single character change that allows for the dash prefix for pre-releases to be optional:

This would to allow for dbt package versions to have greater overlap with PEP 440 even though SemVer 2.0.0 doesn't allow it to be optional.

[joellabes]

Yeah so my point is that if it's no longer the official SEMVER regex, we should update the comment to say something like "based on the SEMVER regex but with tweaks for PEP compatibility"

[jtcohen6]

Converting versions between PyPI and semver provides some useful commentary and code.

It also makes me wonder if we should be using these packages, rather than our own regex:

from semver import Version as SemVersion
from packaging.version import Version as PyPIVersion

def parse_semver_tag(tag):
    version = SemVersion(tag) or PyPIVersion(tag) # probably needs to be try/except
    return str(version)

That's a bigger lift than what we're trying to unblock in this PR.