Subject: [bug#58587] [PATCH 00/14] Introducing pyproject-build-system.

From: Marius Bakke <[email-masked]>
Date: Tue, 18 Oct 2022 23:51:47 +0200

zimoun <[email-masked]> skriver:

> Hi Marius,
>
> On Mon, 17 Oct 2022 at 22:06, Marius Bakke <[email-masked]> wrote:
>
>> I plan to eventually merge it with python-build-system instead of
>> keeping it separate.  Thoughts?
>
> I would suggest to have a clear plan about this transition strategy. :-)
> I mean, if we go to two separated Python build-systems and then merge
> them, we have to write down the various steps; otherwise it could be
> quickly a mess.
>
> For example,
>
>  1. advertise about this new Python build-system
>  2. recommend only this new
>  3. only include package using this new
>  4. convert from old to new
>  5. remove old / rename old to new
>
> or whatever else.  My concern is to have two build systems to maintain
> on the long term.
>
> Once something lands to master and the API, it is then hard to modify.
> Therefore, it appears to me better to draw beforehand the large lines of
> this transition plan.

I tried to address this in the attached documentation patch.

The idea is to:

* Recommend it for new packages in the 'guix' channel, mostly during
  patch review.
* Once we are confident in the implementation, remove the "experimental"
  status and recommend it in the documentation.
* Merge pieces of it into python-build-system as we go, such as sanity
  check changes, using python-toolchain, etc.
* When we "know" that there won't be any major regressions, swap out
  python-build-system with pyproject-build-system entirely and mark the
  latter as deprecated.

Thoughts?

From 628944b6f4267c4eeb5884074298b82c8d17548c Mon Sep 17 00:00:00 2001
From: Marius Bakke <[email-masked]>
Date: Tue, 18 Oct 2022 23:38:39 +0200
Subject: [PATCH] doc: Document pyproject-build-system.

* doc/guix.texi (Build Systems): Add pyproject-build-system section.
* doc/contributing.texi (Python Modules): Mention pyproject.toml and the
PYTHON-TOOLCHAIN package.
---
 doc/contributing.texi | 21 +++++++++++++--------
 doc/guix.texi         | 14 ++++++++++++++
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/doc/contributing.texi b/doc/contributing.texi
index 4b1eed1cb1..b9260267fa 100644
--- a/doc/contributing.texi
+++ b/doc/contributing.texi
@@ -791,7 +791,9 @@ described above.
 
 Dependency information for Python packages is usually available in the
 package source tree, with varying degrees of accuracy: in the
-@file{setup.py} file, in @file{requirements.txt}, or in @file{tox.ini}.
+@file{pyproject.toml} file, the @file{setup.py} file, in
+@file{requirements.txt}, or in @file{tox.ini} (the latter mostly for
+test dependencies).
 
 Your mission, when writing a recipe for a Python package, is to map
 these dependencies to the appropriate type of ``input'' (@pxref{package
@@ -802,10 +804,12 @@ following check list to determine which dependency goes where.
 @itemize
 
 @item
-We currently package Python 2 with @code{setuptools} and @code{pip}
-installed like Python 3.4 has per default.  Thus you don't need to
-specify either of these as an input.  @command{guix lint} will warn you
-if you do.
+We currently package Python with @code{setuptools} and @code{pip}
+installed per default.  This is about to change, and users are encouraged
+to use @code{python-toolchain} if they want a build environment for Python.
+
+@command{guix lint} will warn if @code{setuptools} or @code{pip} are
+added as native-inputs because they are generally not necessary.
 
 @item
 Python dependencies required at run time go into
@@ -814,9 +818,10 @@ Python dependencies required at run time go into
 @file{requirements.txt} file.
 
 @item
-Python packages required only at build time---e.g., those listed with
-the @code{setup_requires} keyword in @file{setup.py}---or only for
-testing---e.g., those in @code{tests_require}---go into
+Python packages required only at build time---e.g., those listed under
+@code{build-system.requires} in @file{pyproject.toml} or with the
+@code{setup_requires} keyword in @file{setup.py}---or dependencies only
+for testing---e.g., those in @code{tests_require} or @file{tox.ini}---go into
 @code{native-inputs}.  The rationale is that (1) they do not need to be
 propagated because they are not needed at run time, and (2) in a
 cross-compilation context, it's the ``native'' input that we'd want.
diff --git a/doc/guix.texi b/doc/guix.texi
index f0fb383005..145aa16afd 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9311,7 +9311,21 @@ instead of the default @code{"out"} output. This is useful for packages that
 include a Python package as only a part of the software, and thus want to
 combine the phases of @code{python-build-system} with another build system.
 Python bindings are a common usecase.
+@end defvr
+
+@defvr {Scheme Variable} pyproject-build-system
+This is a variable exported by @code{guix build-system pyproject}.  It
+is a reimplementation of @code{python-build-system} designed around
+@file{pyproject.toml} and @url{https://peps.python.org/pep-0517/, PEP 517},
+and supports a variety of build backends and test frameworks.
+
+It is considered ``experimental'' in that the implementation details are
+not set in stone yet, however users are encouraged to try it for new
+Python projects (even those using @file{setup.py}) and there should not
+be any breaking changes.
 
+Eventually this build system will be deprecated and merged back into
+@code{python-build-system}, probably some time in 2024.
 @end defvr
 
 @defvr {Scheme Variable} perl-build-system
-- 
2.38.0