projg2 / pycargoebuild

A generator for Rust/Cargo ebuilds written in Python

pycargoebuild

Author:	Michał Górny
License:	GPL-2.0-or-later
Homepage:	https://github.com/projg2/pycargoebuild/

pycargoebuild is a generator for ebuilds using the Cargo infrastructure of Rust language. It is primarily meant to aid in keeping the list of CRATES and their LICENSE up-to-date. It is a rewrite of the cargo-ebuild tool in Python, with no actual dependency on Rust.

pycargoebuild reads Cargo.toml and Cargo.lock files in order to obtain the package's metadata and dependency list, respectively. Then it fetches all dependent crates into DISTDIR and reads their Cargo.toml files to construct the complete list of licenses. The resulting data can either be used to construct a new ebuild from a template or to update the values of CRATES and LICENSE in an existing ebuild.

Why not cargo-ebuild?

pycargoebuild has the following features that cargo-ebuild 0.5.2 is missing:

• small size (cargo-ebuild compiles to 5.5M on my system)
• full support for SPDX-2.0 license expressions with boolean simplification (whereas cargo-ebuild just dumps all licenses it finds)
• pretty-printing with line wrapping for license expressions
• support for updating CRATES and crate LICENSE in existing ebuilds (whereas cargo-ebuild can only generate new ebuilds)
• support for combining the data from multiple subpackages (useful e.g. in setuptools-rust)
• support for fast crate fetching if aria2c is installed
• support for skipping crate licenses (e.g. for when Crates are used at build/test time only)

Usage

To create a new ebuild, run:

pycargoebuild <package-directory>

where package-directory is the directory containing Cargo.toml. This creates an ebuild file named after the package name and version in the current directory, and outputs its name.

To update an existing ebuild, use instead:

pycargoebuild -i <current-file>.ebuild <package-directory>

Note that the existing file must contain both CRATES variable and LICENSE+= assignment like the following:

# Dependent crate licenses
LICENSE+="..."

It is also possible to explicitly specify the output filename using the -o option.

Configuration file

pycargoebuild can additionally be configured using pycargoebuild.toml in one of the XDG config directories (usually ~/.config). The following example provides a quick summary of configuration options available:

[paths]
# default --distdir, Portage config is used if not set
distdir = "/var/cache/portage/distfiles"
# default --license-mapping, "metadata/license-mapping.conf" from
# ::gentoo repo (via Portage API) is used if not set
license-mapping = "/var/db/repos/gentoo/metadata/license-mapping.conf"

[license-overrides]
# provide an SPDX license string for packages missing the metadata
nihav_codec_support = "MIT"
nihav_core = "MIT"
nihav_duck = "MIT"

[license-mapping]
# additional mappings from SPDX licenses to Gentoo licenses
"LicenseRef-UFL-1.0" = "UbuntuFontLicense-1.0"