gh-116811: Ensure MetadataPathFinder.invalidate_caches is reachable when delegated through PathFinder. (#116812)

* Make MetadataPathFinder a proper classmethod.

* In PathFinder.invalidate_caches, also invoke MetadataPathFinder.invalidate_caches.

* Add blurb

3 files changed, 6 insertions, 0 deletions

diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index 46ddcee..b26be85 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1470,6 +1470,9 @@ class PathFinder:
         # https://bugs.python.org/issue45703
         _NamespacePath._epoch += 1
 
+        from importlib.metadata import MetadataPathFinder
+        MetadataPathFinder.invalidate_caches()
+
     @staticmethod
     def _path_hooks(path):
         """Search sys.path_hooks for a finder for 'path'."""
diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
index c612fbe..41c2a4a6 100644
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -797,6 +797,7 @@ class MetadataPathFinder(DistributionFinder):
             path.search(prepared) for path in map(FastPath, paths)
         )
 
+    @classmethod
     def invalidate_caches(cls) -> None:
         FastPath.__new__.cache_clear()
 
diff --git a/Misc/NEWS.d/next/Library/2024-03-14-10-01-23.gh-issue-116811._h5iKP.rst b/Misc/NEWS.d/next/Library/2024-03-14-10-01-23.gh-issue-116811._h5iKP.rst
new file mode 100644
index 0000000..0016863
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-03-14-10-01-23.gh-issue-116811._h5iKP.rst
@@ -0,0 +1,2 @@
+In ``PathFinder.invalidate_caches``, delegate to
+``MetadataPathFinder.invalidate_caches``.