Can I add an include path in a distutils command?

Question

I'm working on packaging a Python interface to a C library. The C library comes as a binary distribution tarball with headers and the compiled library. I want to make a bdist_wheel out of it, along with my built Python extensions, and the headers.

I've written a couple of distutils commands for extracting and installing the library like so:

from distutils.core import Command
from distutils.command.build import build

import os
import tarfile

class ExtractLibraryCommand(Command):
    description = 'extract library from binary distribution'

    def initialize_options(self):
        self.build_lib = None
        self.build_temp = None
        self.library_dist = os.environ.get('LIBRARY_DIST')

    def finalize_options(self):
        self.set_undefined_options('build',
                                   ('build_lib', 'build_lib'),
                                   ('build_temp', 'build_temp'))

        assert os.path.exists(self.library_dist), 'Library dist {} does not exist'.format(self.library_dist)

    def run(self):
        with tarfile.open(self.library_dist, 'r') as tf: 
            tf.extractall(path=self.build_temp)

class InstallLibraryCommand(Command):
    description = 'install library from extracted distribution'

    def initialize_options(self):
        self.build_lib = None
        self.build_temp = None

    def finalize_options(self):
        self.set_undefined_options('build',
                                   ('build_lib', 'build_lib'),
                                   ('build_temp', 'build_temp'))

    def run(self):
            self.copy_tree(
                os.path.join(os.path.join(build_temp, 'my_library')),
                os.path.join(self.build_lib, os.path.join('my_package', 'my_library'))
            )

Then I override the build step to include my new commands.

class BuildCommand(build):
    def run(self):
        self.run_command('extract_library')
        self.run_command('install_library')
        build.run(self)

The problem is, I'm not sure how to get the path to the headers for the library to build my extensions, as they're installed to a directory specified by distutils.

from setuptools import setup, find_packages
from setuptools.extension import Extension
from Cython.Build import cythonize

extensions = [
    Extension(
        'package.library.*',
        ['package/library/*.pyx'],
        include_dirs=???,
    ),
]

setup(
    packages=find_packages(),
    ...
    ext_modules=cythonize(extensions),
)

EDIT: To clarify, this is one setup.py script.

Answer 1

You can modify the extensions in the InstallLibraryCommand, after the library becomes available. I'd probably also move the extraction/installation code to finalize_options instead of run as installing the library in building stage is somewhat late in my opinion (makes the library unavailable in the configuration stage). Example:

class InstallLibraryCommand(Command):
    def finalize_options(self):
        ...
        with tarfile.open(self.library_dist, 'r') as tf: 
            tf.extractall(path=self.build_temp)
        include_path = os.path.join(self.build_lib, os.path.join('my_package', 'my_library'))
        self.copy_tree(
                os.path.join(os.path.join(build_temp, 'my_library')),
                include_path
        )
        for ext in self.distribution.ext_modules:
            ext.include_dirs.append(include_path)