I'm not entirely sure how to handle these version constraint types, but we're using CEq incorrectly here. I think for From you can use CCompatible but we don't have an equivalent for the others yet...

I'm split between saying

• Strip all of the version constraints and leave the version as CEq c or CEq rhs/lhs to ensure that the FOSSA backend can handle the version correctly.
• Leave it the way you have it because its more correct.

Can you test what happens when a locator is sent to the backed with a RhsHalfOpenInterval? I'm concerned that the result won't be what we want. It may be better to do CEq lhs with a note about how we have an issue. You should be able to make a fossa-deps file, type: git, name: <some swift package with the valid constraint>.

[future-work] Alternatively, you could add a type like CRhsHalfOpenInterval to VerConstraint so that we handle this properly when the graph is converted to SrcUnits.

My preference is we go with (2) leave it way it is because it is more correct.

If (1) is followed, we might fail to resolve versions when LHS or RHS of constraint does not exist (not a perfect example but ~ e.g. >= 0.0.0, where 0.0.0 does not exist)

I've validated both RhsHalfOpenInterval, ClosedInterval, and others in unit and integration test for swift fetchers:

• (integration test in fetcher) https://github.com/fossas/FOSSA/pull/6418/files#diff-afd29de33fe5b6b70a89eaaafe634ffae1c7a94d3d081ed77522295b625a942dR83
• (spectrometer unit test) - https://github.com/fossas/spectrometer/pull/354/files#diff-68e91f6fa560fd2d45ebf74cd2eacc278a5fff0d66e2a7d218e9480661a5ae48R71

I'm comfortable with option 2 as well, mainly because of our conversation yesterday about how the Swift fetcher is built to handle these constraints.

Could we actually add a type similar to CRhsHalfOpenInterval and others for this PR? I think that would ease all of my concerns about version handling and it shouldn't be a hard addition. We're going to need it eventually and I think this VersionConstraint would make sure we always handle this version case the same everywhere.