A package version: the raw text as published, plus the parsed ordering key when the text parses. There is deliberately no Ord. Comparison goes through compareVersions.

The parsed, canonical ordering key. Nothing if the raw text did not parse for its ecosystem, in which case ordering rules abstain.

The version's key under an ecosystem's grammar, as mkVersion for that ecosystem builds it. It reuses the key the version carries when that key is the ecosystem's, and parses otherwise.

Build a Version, parsing and evaluating a canonical key when possible. Total: an unparseable version is still represented, keyless, so a proxy never drops one over a parser gap.

Render a version in wire form: the raw text, verbatim as published.

Compare two versions by their canonical keys. Nothing when either version has no key, in which case an ordering-based rule abstains.

The parsed, canonical, comparable form of a version. The type is opaque and parseVersionKey is its only constructor, so the comparator cannot see non-canonical input.

Parse raw version text into a canonical VersionKey for its ecosystem, or report why it did not parse. The Ord on the result is meaningful only within one ecosystem.

Why a version string failed to parse.

Whether a parsed version is a stable (final, non-prerelease) release, under its own ecosystem's notion of one.

>>> isStable <$> parseVersionKey Npm "1.0.0"
Right True
>>> isStable <$> parseVersionKey Npm "1.0.0-rc.1"
Right False
>>> isStable <$> parseVersionKey PyPI "1.0.post1"
Right True
>>> isStable <$> parseVersionKey PyPI "1.0a1.dev2"
Right False
>>> isStable <$> parseVersionKey RubyGems "1.0.0.pre"
Right False

The one spelling a PEP 440 version canonicalises to, which a PyPI projection keys by so two spellings of one release merge. The raw spelling survives per artifact through the filename.

>>> canonicalPep440 "1.0.0"
Just "1"
>>> canonicalPep440 "not-a-version"
Nothing

Resolve dist-tags.latest over the survivors the caller left, keeping chosen when it survives so a prerelease never displaces a maintainer's stable tag. The result is a survivor.