Improve atomicity when writing PKG-INFOdev/core_metadata

For the time being, when `setuptools.build_meta` is called,
`egg_info.egg_base` is accidentally set to the project root between the
several calls to the different build hooks.

This means that if the hooks are called, they will try to overwrite
`setuptools.egg-info/PKG-INFO`, and for a very short interval of time it
will be an empty file.

Another process may then try to simultaneously use `importlib.metadata`
to list entry-points. However to sort entry-points, `importlib.metadata`
will try to read the `Name` field in the `PKG-INFO/METADATA` files and
will raise an error/warning if that file is empty.

This commit tries to use `os.replace` to avoid having an empty PKG-INFO
while `importlib.metadata` is used.

1 files changed, 3 insertions, 1 deletions

diff --git a/setuptools/monkey.py b/setuptools/monkey.py
index 23a5832d..5154d4c7 100644
--- a/setuptools/monkey.py
+++ b/setuptools/monkey.py
@@ -100,7 +100,9 @@ def patch_all():
 
 def _patch_distribution_metadata():
     """Patch write_pkg_file and read_pkg_file for higher metadata standards"""
-    for attr in ('write_pkg_file', 'read_pkg_file', 'get_metadata_version'):
+    for attr in (
+        'write_pkg_info', 'write_pkg_file', 'read_pkg_file', 'get_metadata_version'
+    ):
         new_val = getattr(setuptools._core_metadata, attr)
         setattr(distutils.dist.DistributionMetadata, attr, new_val)