don't merge python_version and python_full_version

[dimbleby]

These markers are not quite equivalent; I've updated the relevant testcases to give examples where the previous code got it wrong.

cf python-poetry/poetry#5717

I do not claim that this is the only code that confuses python_version and python_full_version, I just remember this particular example because I wrote it myself!

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[neersighted]

LGTM, but I'm curious how we got here -- did everyone just conflate the two of these together and not realize the subtle difference (that python_version is basically always .0, if I understand correctly)? Can we add some documentation somewhere that explicitly defines the intention for each of these (or link to the upstream docs)?

[dimbleby]

python_version is basically always .0 ...

that's not wrong exactly, but thinking that way is pretty much the misconception that I had when introducing the code that this MR is now removing.

python_version x.y and python_full_version x.y.0 are not interchangeable. Eg python_version > 3.6 is more like python_full_version >= 3.7.0 than it is like python_full_version > 3.6.0.

[neersighted]

python_version is basically always .0 ...

that's not wrong exactly, but thinking that way is pretty much the misconception that I had when introducing the code that this MR is now removing.

python_version x.y and python_full_version x.y.0 are not interchangeable. Eg python_version > 3.6 is more like python_full_version >= 3.7.0 than it is like python_full_version > 3.6.0.

See, that's definitely needed somewhere in this codebase... Any thoughts on a good place to document it or link to docs?

[dimbleby]

I don't know where would be a good place to put this. Use of these markers is scattered around the codebases: wherever one wrote this down, I'd think there's a good chance that the next person wouldn't happen to find it.

Open to suggestions!

Might be better to continue this part of the discussion in python-poetry/poetry#5717 which I intended to cover the general issue, this MR is only a specific example of getting it wrong.