gh-151788: Address review — OSError fallback and tone down NEWS

- Wrap entry.is_dir()/is_symlink() in try/except OSError, falling back to
  False to exactly mirror os.path.isdir()/islink() (matches os.walk()).
- Reword the NEWS entry to avoid speedup-multiplier claims; describe it as
  improving list_directory() on systems with slow stat calls.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mjbommar

Lib/http/server.py

@@ -902,13 +902,22 @@ def list_directory(self, path):
         for entry in entries:
             name = entry.name
             displayname = linkname = name
-            # Append / for directories or @ for symbolic links.
-            # Use cached os.DirEntry methods to avoid a stat() per entry,
-            # which is costly on network filesystems such as NFS.
-            if entry.is_dir():
+            # Append / for directories or @ for symbolic links. Use the cached
+            # os.DirEntry methods to avoid a stat() per entry. Fall back to
+            # False on OSError to mirror os.path.isdir()/islink(), whose result
+            # would otherwise differ (e.g. a symlink to an unreadable target).
+            try:
+                is_dir = entry.is_dir()
+            except OSError:
+                is_dir = False
+            try:
+                is_symlink = entry.is_symlink()
+            except OSError:
+                is_symlink = False
+            if is_dir:
                 displayname = name + "/"
                 linkname = name + "/"
-            if entry.is_symlink():
+            if is_symlink:
                 displayname = name + "@"
                 # Note: a link to a directory displays with @ and links with /
             r.append('<li><a href="%s">%s</a></li>'

Misc/NEWS.d/next/Library/2026-06-20-09-00-26.gh-issue-151788.Gr8IxK.rst

@@ -1,4 +1,5 @@
-Speed up :class:`http.server.SimpleHTTPRequestHandler` directory listings by
-using :func:`os.scandir` instead of :func:`os.listdir` plus an :func:`os.stat`
-call per entry. This is faster on all filesystems and especially on network
-filesystems such as NFS.
+:class:`http.server.SimpleHTTPRequestHandler` now builds directory listings
+with :func:`os.scandir` instead of :func:`os.listdir` followed by an
+:func:`os.stat` call per entry. This improves the performance of
+:meth:`~http.server.SimpleHTTPRequestHandler.list_directory` on systems with
+slow ``stat`` calls, such as network filesystems.