fast-semver-rs

Opt-in Rust-backed, behavior-compatible API replacement for semver==3.0.4. It keeps the semver import, Version/VersionInfo Python class, CLI and deprecated compatibility surface while accelerating the strict parse hot path.

Rust does not replace Python's public object model. Bytes decoding, subclasses, optional minor/patch parsing, arbitrary-size integers, exact errors, bumps, matching, formatting, CLI and warnings remain in the frozen Python compatibility layer. The native parser is used only when it can preserve that contract.

Verified release evidence

• frozen upstream tag 3.0.4 at commit 6adf8765f6e21910f1f0c13151ce84f32f8d431d;
• exact native and universal fallback wheel suites: 337 passed each (329 frozen upstream plus 8 candidate regressions);
• 10,000 deterministic valid, invalid, bytes, optional-part and arbitrary-integer cases produced identical results or exact exceptions;
• Google OSV semver_index applicable suite: Oracle and Candidate 3 passed each;
• exact macOS arm64 wheel, 15-pair local evidence: parse 1.72x, compare 1.32x, match 1.40x median speedup with identical output digests;
• Google OSV 20,000-version exact-wheel evidence: normalize 1.21x, sort 1.15x, identical digests;
• native wheel, universal fallback wheel and sdist passed strict metadata, RECORD, namespace, console-script, cache/test/binary sanitation and Twine checks.

Every release is gated on reproducing this contract across five native platforms, publishing one audited seven-artifact set, public native and universal-fallback reinstalls, and creating the GitHub Release last. The timings remain observations from named runners and artifacts, not universal speed claims.

Distribution limitation

The distribution name is fast-semver-rs, while existing consumers depend on the separate semver distribution. Package resolvers do not treat one as satisfying the other even though both provide the semver namespace. The controlled opt-in flow after release will therefore be:

python -m pip uninstall -y semver
python -m pip install fast-semver-rs
python -c "from semver import Version; print(Version.parse('1.2.3-rc.1'))"

Do not install both distributions together. Roll back with python -m pip uninstall -y fast-semver-rs && python -m pip install 'semver==3.0.4'. An upstream optional native backend is the preferred broad-adoption path; no upstream acceptance is claimed.

Development

uv venv --python 3.14 .venv
uv pip install --python .venv/bin/python maturin pytest pytest-cov pytest-randomly
.venv/bin/maturin develop --release
.venv/bin/python -m pytest -q tests upstream/tests

BSD-3-Clause. See THIRD_PARTY_NOTICES.md before redistribution.