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.

A special <distribution name and version>.pth file is also added to the distribution. When the wheel is installed this .pth file triggers the post-install logic via wheel-axle-runtime.

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.