Wheel Axle - Python Wheel enhancement library

Problem

1. Python wheel does not support symlinks.
2. Python wheel does not support overwriting in a convenient way:
   • whether the distribution is pure-Python
   • distribution ABI tag
   • extend Python tag override capability

Solution

WARNING: THIS IS EXPERIMENTAL BETA SOFTWARE. THERE ARE NO WARRANTIES OF ANY KIND. USE AT YOUR OWN RISK. ADDITIONAL INCLUDED DISCLAIMERS ALSO APPLY.

Wheel-Axle (axle, bdist_axle) is a drop-in replacement/augmentation utility for wheel (bdist_wheel) that extends and builds spec-compliant wheels.

During the build, axle is able to capture and record in the Python wheel the symlinks in the following schema paths (locations):

• purelib
• platlib
• scripts
• headers
• data

Additionally, Axle is able to customize the Python wheel tags via additional command line options.

While the generated Python wheel is fully spec-compliant, additional symlink functionality is not possible without its companion library Wheel Axle Runtime. Thus, every Python wheel generated by the bdist_axle automatically becomes dependent on wheel-axle-runtime that provides post-install logic required.

Implementation

The body of the library is as ugly and messy as distutils/setuptools are, and consists of, mainly, in hacking/overwriting various setuptools commands to detect, handle and record symlinks and their targets. Once that problem is solved, the list of symlinks is recorded in the .dist-info/symlinks.txt in the following CSV format:

1. symlink name
2. symlink target
3. a boolean (0 or 1) flag indicating whether the target is a directory

NOTE: Symlinks may be relative, absolute and/or broken. Symlink targets are recorded verbatim (even when broken) and are NOT otherwise interpreted. THIS IS INTENTIONAL. Please see Wheel Axle Runtime Security Notice for additional information.

Two special startup files are also added to the distribution, and whichever one the running interpreter honors triggers the post-install logic via wheel-axle-runtime:

• <distribution name and version>.pth, whose import line site executes up to Python 3.17
• <distribution name and version>.start, a PEP 829 startup entry point file honored from Python 3.15 on, whose mere presence also suppresses the import line of the matching .pth

NOTE: wheels built by bdist_axle before 0.0.13 only carry the .pth file, and its import line relies on a site implementation detail that Python 3.15 removed. Those wheels fail to install their symlinks on Python 3.15 and have to be rebuilt with bdist_axle 0.0.13 or later. Please see the Wheel Axle Runtime compatibility notes for details.

Usage

python setup.py bdist_wheel <arguments> can be replaced with python setup.py bdist_axle <arguments>. The replacement is drop-in.

Additional functionality is available via the following options:

  --python-tag        Python implementation compatibility tag (default: 'py3')
  --root-is-pure      set to manually override whether the wheel is
                      pure (default: None)
  --abi-tag           set to override ABI tag (default: None)
  --require-libpython set to indicate the package requires libpython in the
                       exec_prefix/platlib

Using --python-tag, --root-is-pure and --abi-tag allows you to create wheels that carry platform-dependent data while otherwise containing pure-Python libraries.