gh-89727: Fix os.walk RecursionError on deep trees

Lib/test/support/__init__.py

@@ -2178,19 +2178,23 @@ def check_disallow_instantiation(testcase, tp, *args, **kwds):
     testcase.assertRaisesRegex(TypeError, msg, tp, *args, **kwds)
 
 @contextlib.contextmanager
+def temp_recursion_limit(limit):
+    """Temporarily change the recursion limit."""
+    original_limit = sys.getrecursionlimit()
+    try:
+        sys.setrecursionlimit(limit)
+        yield
+    finally:
+        sys.setrecursionlimit(original_limit)
+
 def infinite_recursion(max_depth=75):
     """Set a lower limit for tests that interact with infinite recursions
     (e.g test_ast.ASTHelpers_Test.test_recursion_direct) since on some
     debug windows builds, due to not enough functions being inlined the
     stack size might not handle the default recursion limit (1000). See
     bpo-11105 for details."""
+    return temp_recursion_limit(max_depth)
 
-    original_depth = sys.getrecursionlimit()
-    try:
-        sys.setrecursionlimit(max_depth)
-        yield
-    finally:
-        sys.setrecursionlimit(original_depth)
 
 def ignore_deprecations_from(module: str, *, like: str) -> object:
     token = object()

Lib/test/test_os.py

@@ -33,6 +33,7 @@
 from test.support import import_helper
 from test.support import os_helper
 from test.support import socket_helper
+from test.support import temp_recursion_limit
 from test.support import warnings_helper
 from platform import win32_is_iot
 
@@ -1471,6 +1472,12 @@ def test_walk_many_open_files(self):
                 self.assertEqual(next(it), expected)
             p = os.path.join(p, 'd')
 
+    def test_walk_above_recursion_limit(self):
+        os.makedirs(os.path.join(self.walk_path, *(['d'] * 50)))
+        with temp_recursion_limit(50):
+            all = list(self.walk(self.walk_path))
+        self.assertEqual(len(all), 54)
+
 
 @unittest.skipUnless(hasattr(os, 'fwalk'), "Test needs os.fwalk()")
 class FwalkTests(WalkTests):
@@ -1545,6 +1552,8 @@ def test_fd_leak(self):
 
     # fwalk() keeps file descriptors open
     test_walk_many_open_files = None
+    # fwalk() still uses recursion
+    test_walk_above_recursion_limit = None
 
 
 class BytesWalkTests(WalkTests):