packaging-rust (Rust mirror of pypa/packaging)

Stage-1 Rust mirror of pypa/packaging (Apache-2.0 OR BSD-2-Clause). Behavior-identical port of src/packaging/*.py exposed as the packaging._packaging extension module via PyO3, with thin packaging/*.py re-export shims preserving the original public API (Version, SpecifierSet, Requirement, Marker, sys_tags, ...).

Layout (publishable)

One implementation, two distributions:

• packaging-core/ — reusable pure-Rust core crate packaging-rust-core (crates.io). No Python dependency: rlib, cargo test clean. Rust consumers depend on this crate directly.
• src/lib.rs — thin PyO3 binding crate packaging-rust calling that same core. Ships on PyPI as distribution packaging-rust; the import name is unchanged (import packaging), so users swap the install with zero code changes: pip install packaging-rust instead of pip install packaging.
• packaging/ — Python shims (one per original module; errors.py keeps the original version-branch glue verbatim since it selects the stdlib ExceptionGroup on 3.11+).
• release.toml — release configuration (names, version, platforms, Python versions, publishing repo + workflow identity, license, upstream attribution). Read by rustsmith release-prep; see docs/RELEASE.md.

No redesign: same parsing, same ordering, same error messages.

Install

pip install packaging-rust
python -c "from packaging.version import Version; print(Version('1.0'))"

Measured performance

No accepted optimizations yet (mirror baseline); re-run release-prep after run --stage optimize merges winners. Artifact hashes are intentionally absent here; see release-manifest.json.