[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)

1 files changed, 2 insertions, 1 deletions

diff --git a/pyproject.toml b/pyproject.toml
index 38c5a47d62..4a583ee5a3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,4 @@
 [build-system]
 requires = ["setuptools >= 39.2.0", "wheel"]
-build-backend = "setuptools.build_meta"
+backend-path = ["packaging"]  # requires 'Pip>=20' or 'pep517>=0.6.0'
+build-backend = "pep517_backend.hooks"  # wraps `setuptools.build_meta`