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konsti 889f6173cc
Unify python interpreter abstractions (#178) 
Previously, we had two python interpreter metadata structs, one in
gourgeist and one in puffin. Both would spawn a subprocess to query
overlapping metadata and both would appear in the cli crate, if you
weren't careful you could even have to different base interpreters at
once. This change unifies this to one set of metadata, queried and
cached once.

Another effect of this crate is proper separation of python interpreter
and venv. A base interpreter (such as `/usr/bin/python/`, but also pyenv
and conda installed python) has a set of metadata. A venv has a root and
inherits the base python metadata except for `sys.prefix`, which unlike
`sys.base_prefix`, gets set to the venv root. From the root and the
interpreter info we can compute the paths inside the venv. We can reuse
the interpreter info of the base interpreter when creating a venv
without having to query the newly created `python`.
2023-10-25 20:11:36 +00:00
..
pep440_rs Unify python interpreter abstractions (#178) 2023-10-25 20:11:36 +00:00
Readme.md Copy over pep440-rs crate (#30) 2023-10-06 20:11:52 -04:00

Readme.md

PEP440 in rust

A library for python version numbers and specifiers, implementing PEP 440

pip install pep440_rs

from pep440_rs import Version, VersionSpecifier

assert Version("1.1a1").any_prerelease()
assert Version("1.1.dev2").any_prerelease()
assert not Version("1.1").any_prerelease()
assert VersionSpecifier(">=1.0").contains(Version("1.1a1"))
assert not VersionSpecifier(">=1.1").contains(Version("1.1a1"))
assert Version("2.0") in VersionSpecifier("==2")

Unlike pypa/packaging, this library always matches preleases. To only match final releases, filter with .any_prelease() beforehand.

PEP 440 has a lot of unintuitive features, including:

  • An epoch that you can prefix the version which, e.g. 1!1.2.3. Lower epoch always means lower version (1.0 <=2!0.1)
  • post versions, which can be attached to both stable releases and prereleases
  • dev versions, which can be attached to sbpth table releases and prereleases. When attached to a prerelease the dev version is ordered just below the normal prerelease, however when attached to a stable version, the dev version is sorted before a prereleases
  • prerelease handling is a mess: "Pre-releases of any kind, including developmental releases, are implicitly excluded from all version specifiers, unless they are already present on the system, explicitly requested by the user, or if the only available version that satisfies the version specifier is a pre-release.". This means that we can't say whether a specifier matches without also looking at the environment
  • prelease vs. prerelease incl. dev is fuzzy
  • local versions on top of all the others, which are added with a + and have implicitly typed string and number segments
  • no semver-caret (^), but a pseudo-semver tilde (~=)
  • ordering contradicts matching: We have e.g. 1.0+local > 1.0 when sorting, but ==1.0 matches 1.0+local. While the ordering of versions itself is a total order the version matching needs to catch all sorts of special cases