Builds with ament_python broken with sphinx >= 7.0.0

[oysstu]

The following way of obtaining a list of available commands from setup.py is broken on sphinx v7.0.0 and later.

colcon-core/colcon_core/task/python/build.py

Lines 170 to 185 in 99c0326

	async def _get_available_commands(self, path, env):
	output = await check_output(
	[executable, 'setup.py', '--help-commands'], cwd=path, env=env)
	commands = set()
	for line in output.splitlines():
	if not line.startswith(b' '):
	continue
	try:
	index = line.index(b' ', 2)
	except ValueError:
	continue
	if index == 2:
	continue
	commands.add(
	line[2:index].decode(locale.getpreferredencoding(False)))
	return commands

This occurs because the setuptools integration is deprecated:
sphinx-doc/sphinx#9595 (comment)

The end result is that ament_python continues as normal, but installs the package as an egg without the egg-info.

colcon-core/colcon_core/task/python/build.py

Line 92 in 99c0326

if 'egg_info' in available_commands:

When building ros, the build will fail on ament_cmake_core because it cannot find ament_package. Egg modules are not imported even if the site-packages directory is in the python-path. It's possible to add something like this to make the egg import

import site
import os
site.addsitedir(os.path.split(__file__)[0])

However, there's further breakage later in the build process in cmake, as it expects template files in a certain location (and not inside the compressed egg).

[14mRh4X0r]

Funnily enough, this actually seems to be a bug with Sphinx. I've filed a PR with them: sphinx-doc/sphinx#11418

[oysstu]

Resolved in sphinx 7.0.1