From 9cc23db56add79357b8f8257fe6fc0d6879d4579 Mon Sep 17 00:00:00 2001
From: "Andrew J. Hesford" <ajh@sideband.org>
Date: Fri, 21 Jul 2023 09:50:00 -0400
Subject: [PATCH] Fix builds with Cython 3

This is a *de minimis* fix for building with Cython 3. Recent Cython<3
releases provided `Cython.Distutils.build_ext` as an alias to
`Cython.Distutils.old_build_ext.old_build_ext`; Cython 3 drops this
alias and instead uses a wholly new `Cython.Distutils.build_ext` that
does not provide the `cython_sources` function used in `setup.py`.

Explicitly importing `old_build_ext` preserves the existing behavior for
recent Cython<3 and uses the correct behavior for Cython 3. Should the
import fail (*e.g.*, because the version of Cython available predates
the availability of `old_build_ext`), the import falls back to just
`Cython.Distutils.build_ext`.

Signed-off-by: Andrew J. Hesford <ajh@sideband.org>
Upstream-Status: Denied [https://github.com/yaml/pyyaml/pull/731]
Signed-off-by: Alexander Kanavin <alex@linutronix.de>
---
 pyproject.toml | 2 +-
 setup.py       | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 4bc04c0..2bf5ec8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools", "wheel", "Cython<3.0"]
+requires = ["setuptools", "wheel", "Cython"]
 build-backend = "setuptools.build_meta"
diff --git a/setup.py b/setup.py
index 65b0ea0..4461580 100644
--- a/setup.py
+++ b/setup.py
@@ -82,7 +82,11 @@ if 'sdist' in sys.argv or os.environ.get('PYYAML_FORCE_CYTHON') == '1':
     with_cython = True
 try:
     from Cython.Distutils.extension import Extension as _Extension
-    from Cython.Distutils import build_ext as _build_ext
+    try:
+        from Cython.Distutils.old_build_ext import old_build_ext as _build_ext
+    except ImportError:
+        from Cython.Distutils import build_ext as _build_ext
+
     with_cython = True
 except ImportError:
     if with_cython:
-- 
2.39.2