Merge branch 'main' into gh-73991-rmtree

Lib/os.py

@@ -281,9 +281,8 @@ def renames(old, new):
 
 __all__.extend(["makedirs", "removedirs", "renames"])
 
-# Private sentinel that can be passed to os.walk() to classify all symlinks as
-# files, and walk into every path classified as a directory (potentially after
-# user modification in topdown mode). Used by pathlib.Path.walk().
+# Private sentinel that makes walk() classify all symlinks and junctions as
+# regular files.
 _walk_symlinks_as_files = object()
 
 def walk(top, topdown=True, onerror=None, followlinks=False):
@@ -501,11 +500,38 @@ def _fwalk(stack, isbytes, topdown, onerror, follow_symlinks):
         # necessary, it can be adapted to only require O(1) FDs, see issue
         # #13734.
 
+        action, value = stack.pop()
+        if action == _fwalk_close:
+            close(value)
+            return
+        elif action == _fwalk_yield:
+            yield value
+            return
+        assert action == _fwalk_walk
+        isroot, dirfd, toppath, topname, entry = value
         try:
-            scandir_it = scandir(topfd)
-        except OSError as error:
-            error.filename = toppath
-            raise
+            if not follow_symlinks:
+                # Note: To guard against symlink races, we use the standard
+                # lstat()/open()/fstat() trick.
+                if entry is None:
+                    orig_st = stat(topname, follow_symlinks=False, dir_fd=dirfd)
+                else:
+                    orig_st = entry.stat(follow_symlinks=False)
+            topfd = open(topname, O_RDONLY | O_NONBLOCK, dir_fd=dirfd)
+        except OSError as err:
+            if isroot:
+                raise
+            if onerror is not None:
+                onerror(err)
+            return
+        stack.append((_fwalk_close, topfd))
+        if not follow_symlinks:
+            if isroot and not st.S_ISDIR(orig_st.st_mode):
+                return
+            if not path.samestat(orig_st, stat(topfd)):
+                return
+
+        scandir_it = scandir(topfd)
         dirs = []
         nondirs = []
         entries = None if topdown or follow_symlinks else []
@@ -533,36 +559,15 @@ def _fwalk(stack, isbytes, topdown, onerror, follow_symlinks):
         else:
             stack.append((_fwalk_yield, (toppath, dirs, nondirs, topfd)))
 
-        for name in dirs if entries is None else zip(dirs, entries):
-            try:
-                if not follow_symlinks:
-                    if topdown:
-                        orig_st = stat(name, dir_fd=topfd, follow_symlinks=False)
-                    else:
-                        assert entries is not None
-                        name, entry = name
-                        orig_st = entry.stat(follow_symlinks=False)
-                dirfd = open(name, O_RDONLY | O_NONBLOCK, dir_fd=topfd)
-            except OSError as err:
-                if onerror is not None:
-                    onerror(err)
-                continue
-            try:
-                if follow_symlinks or path.samestat(orig_st, stat(dirfd)):
-                    dirpath = path.join(toppath, name)
-                    yield from _fwalk(dirfd, dirpath, isbytes,
-                                      topdown, onerror, follow_symlinks)
-            finally:
-                try:
-                    close(dirfd)
-                except OSError as err:
-                    err.filename = path.join(toppath, name)
-                    if onerror is not None:
-                        onerror(err)
-                    continue
-
-        if not topdown:
-            yield toppath, dirs, nondirs, topfd
+        toppath = path.join(toppath, toppath[:0])  # Add trailing slash.
+        if entries is None:
+            stack.extend(
+                (_fwalk_walk, (False, topfd, toppath + name, name, None))
+                for name in dirs[::-1])
+        else:
+            stack.extend(
+                (_fwalk_walk, (False, topfd, toppath + name, name, entry))
+                for name, entry in zip(dirs[::-1], entries[::-1]))
 
     __all__.append("fwalk")