[backport-2.14] 📦 Integrate manpage builds into PEP 517 build backend (#80129)

This patch creates a thin wrapper around the `setuptools`' PEP 517
build backend in-tree. It features an ability to request generating
the manpage files in the process of building a source distribution.
This toggle is implemented using the `config_settings` mechanism of
PEP 517.
One must explicitly pass it a CLI option to the build front-end to
trigger said behavior. The packagers are expected to use the
following call:

    python -m build --config-setting=--build-manpages

This option has no effect on building wheels.

🧪 The change includes integration tests

This test runs building and re-building sdists and wheels with and
without the `--build-manpages` config setting under the
oldest-supported and new `setuptools` pinned.

It is intended to preserve the interoperability of the packaging setup
across Python runtimes.

An extra smoke test also verifies that non PEP 517 interfaces remain functional.

PR #79606

Co-authored-by: Matt Clay <matt@mystile.com>
(cherry picked from commit 56036013cd09db0f1b20402a69be44345ddafb22)

3 files changed, 118 insertions, 0 deletions

diff --git a/packaging/pep517_backend/__init__.py b/packaging/pep517_backend/__init__.py
new file mode 100644
index 0000000000..1d3bc14c82
--- /dev/null
+++ b/packaging/pep517_backend/__init__.py
@@ -0,0 +1 @@
+"""PEP 517 build backend for optionally pre-building docs before setuptools."""
diff --git a/packaging/pep517_backend/_backend.py b/packaging/pep517_backend/_backend.py
new file mode 100644
index 0000000000..9adbc50f2f
--- /dev/null
+++ b/packaging/pep517_backend/_backend.py
@@ -0,0 +1,108 @@
+"""PEP 517 build backend wrapper for optionally pre-building docs for sdist."""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+from configparser import ConfigParser
+from importlib.metadata import import_module
+from pathlib import Path
+
+from setuptools.build_meta import (
+    build_sdist as _setuptools_build_sdist,
+    get_requires_for_build_sdist as _setuptools_get_requires_for_build_sdist,
+)
+
+
+__all__ = (  # noqa: WPS317, WPS410
+    'build_sdist', 'get_requires_for_build_sdist',
+)
+
+
+def _make_in_tree_ansible_importable() -> None:
+    """Add the library directory to module lookup paths."""
+    lib_path = str(Path.cwd() / 'lib/')
+    os.environ['PYTHONPATH'] = lib_path  # NOTE: for subprocesses
+    sys.path.insert(0, lib_path)  # NOTE: for the current runtime session
+
+
+def _get_package_distribution_version() -> str:
+    """Retrieve the current version number from setuptools config."""
+    setup_cfg_path = Path.cwd() / 'setup.cfg'
+    setup_cfg = ConfigParser()
+    setup_cfg.read_string(setup_cfg_path.read_text())
+    cfg_version = setup_cfg.get('metadata', 'version')
+    importable_version_str = cfg_version.removeprefix('attr: ')
+    version_mod_str, version_var_str = importable_version_str.rsplit('.', 1)
+    return getattr(import_module(version_mod_str), version_var_str)
+
+
+def _generate_rst_in_templates() -> Path:
+    """Create ``*.1.rst.in`` files out of CLI Python modules."""
+    generate_man_cmd = (
+        sys.executable,
+        'hacking/build-ansible.py',
+        'generate-man',
+        '--template-file=docs/templates/man.j2',
+        '--output-dir=docs/man/man1/',
+        '--output-format=man',
+        *Path('lib/ansible/cli/').glob('*.py'),
+    )
+    subprocess.check_call(tuple(map(str, generate_man_cmd)))
+    return Path('docs/man/man1/').glob('*.1.rst.in')
+
+
+def _convert_rst_in_template_to_manpage(rst_in, version_number) -> None:
+    """Render pre-made ``*.1.rst.in`` templates into manpages.
+
+    This includes pasting the hardcoded version into the resulting files.
+    The resulting ``in``-files are wiped in the process.
+    """
+    templated_rst_doc = rst_in.with_suffix('')
+    templated_rst_doc.write_text(
+        rst_in.read_text().replace('%VERSION%', version_number))
+
+    rst_in.unlink()
+
+    rst2man_cmd = (
+        sys.executable,
+        Path(sys.executable).parent / 'rst2man.py',
+        templated_rst_doc,
+        templated_rst_doc.with_suffix(''),
+    )
+    subprocess.check_call(tuple(map(str, rst2man_cmd)))
+    templated_rst_doc.unlink()
+
+
+def build_sdist(  # noqa: WPS210, WPS430
+         sdist_directory: os.PathLike,
+         config_settings: dict[str, str] | None = None,
+) -> str:
+    build_manpages_requested = '--build-manpages' in (
+        config_settings or {}
+    )
+    if build_manpages_requested:
+        Path('docs/man/man1/').mkdir(exist_ok=True, parents=True)
+        _make_in_tree_ansible_importable()
+        version_number = _get_package_distribution_version()
+        for rst_in in _generate_rst_in_templates():
+            _convert_rst_in_template_to_manpage(rst_in, version_number)
+
+    return _setuptools_build_sdist(
+        sdist_directory=sdist_directory,
+        config_settings=config_settings,
+    )
+
+
+def get_requires_for_build_sdist(
+        config_settings: dict[str, str] | None = None,
+) -> list[str]:
+    return _setuptools_get_requires_for_build_sdist(
+        config_settings=config_settings,
+    ) + [
+        'docutils',  # provides `rst2man`
+        'jinja2',  # used in `hacking/build-ansible.py generate-man`
+        'straight.plugin',  # used in `hacking/build-ansible.py` for subcommand
+        'pyyaml',  # needed for importing in-tree `ansible-core` from `lib/`
+    ]
diff --git a/packaging/pep517_backend/hooks.py b/packaging/pep517_backend/hooks.py
new file mode 100644
index 0000000000..b834338a6d
--- /dev/null
+++ b/packaging/pep517_backend/hooks.py
@@ -0,0 +1,9 @@
+# -*- coding: utf-8 -*-
+
+"""PEP 517 build backend for optionally pre-building docs before setuptools."""
+
+from setuptools.build_meta import *  # Re-exporting PEP 517 hooks  # pylint: disable=unused-wildcard-import,wildcard-import
+
+from ._backend import (  # noqa: WPS436  # Re-exporting PEP 517 hooks
+    build_sdist, get_requires_for_build_sdist,
+)