From 9f4ee6faa6d7f16d357957265d5181fbd77eeefe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Filipe=20La=C3=ADns?= <lains@riseup.net>
Date: Tue, 26 Oct 2021 01:19:35 +0100
Subject: [PATCH] bpo-45545: premptively fail on contextlib.chdir if we can't
 chdir back
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Signed-off-by: Filipe Laíns <lains@riseup.net>
---
 Lib/contextlib.py                                          | 7 ++++++-
 .../next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst  | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst

diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index ee722585057..e8188105fde 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -774,7 +774,12 @@ class chdir(AbstractContextManager):
         self._old_cwd = []
 
     def __enter__(self):
-        self._old_cwd.append(os.getcwd())
+        # try to chdir to the current cwd so that we preemptively fail if we are
+        # unnable to chdir back to it, see bpo-45545
+        old_cwd = os.getcwd()
+        os.chdir(old_cwd)
+
+        self._old_cwd.append(old_cwd)
         os.chdir(self.path)
 
     def __exit__(self, *excinfo):
diff --git a/Misc/NEWS.d/next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst b/Misc/NEWS.d/next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst
new file mode 100644
index 00000000000..e1fdbacfaaf
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-10-26-01-22-33.bpo-45545.QvsfXK.rst
@@ -0,0 +1,2 @@
+Premptively fail in :func:`contextdir.chdir` if we can't change back to the
+original directory.