Avoid iterating over entry-points while an empty .egg-info exists in sys.path (#4680)

Author: abravalheri

.github/workflows/main.yml

@@ -100,7 +100,7 @@ jobs:
         run: |
           rm -rf dist
           # workaround for pypa/setuptools#4333
-          pipx run --pip-args 'pyproject-hooks<1.1' build
+          pipx run --pip-args 'pyproject-hooks!=1.1' build
           echo "PRE_BUILT_SETUPTOOLS_SDIST=$(ls dist/*.tar.gz)" >> $GITHUB_ENV
           echo "PRE_BUILT_SETUPTOOLS_WHEEL=$(ls dist/*.whl)" >> $GITHUB_ENV
           rm -rf setuptools.egg-info  # Avoid interfering with the other tests

newsfragments/4680.bugfix.rst

@@ -0,0 +1,4 @@
+Changed ``egg_info`` command to avoid adding an empty ``.egg-info`` while
+iterating over entry-points is available in ``sys.path``.
+This avoids triggering integration problems with ``importlib.metadata``/``importlib_metadata``
+(reference: pypa/pyproject-hooks#206).

pyproject.toml

@@ -57,7 +57,7 @@ test = [
 	"pytest-subprocess",
 
 	# workaround for pypa/pyproject-hooks#206
-	"pyproject-hooks<1.1",  # TODO: fix problem with egg-info, see #4670
+	"pyproject-hooks!=1.1",
 
 	"jaraco.test",
 ]

setuptools/command/egg_info.py

@@ -293,13 +293,17 @@ def delete_file(self, filename):
             os.unlink(filename)
 
     def run(self):
+        # Pre-load to avoid iterating over entry-points while an empty .egg-info
+        # exists in sys.path. See pypa/pyproject-hooks#206
+        writers = list(metadata.entry_points(group='egg_info.writers'))
+
         self.mkpath(self.egg_info)
         try:
             os.utime(self.egg_info, None)
         except OSError as e:
             msg = f"Cannot update time stamp of directory '{self.egg_info}'"
             raise distutils.errors.DistutilsFileError(msg) from e
-        for ep in metadata.entry_points(group='egg_info.writers'):
+        for ep in writers:
             writer = ep.load()
             writer(self, ep.name, os.path.join(self.egg_info, ep.name))