From 5af46f3d4e8264c50ffd635dbb395199670e70b7 Mon Sep 17 00:00:00 2001
From: Yutian Li <hotpxless@gmail.com>
Date: Thu, 9 May 2024 14:04:58 -0400
Subject: [PATCH] Fix crashing under squashfuse_ll read-only mounts (#12301)

Fixes #12300
---
 AUTHORS                          | 1 +
 changelog/12300.bugfix.rst       | 1 +
 src/_pytest/assertion/rewrite.py | 5 ++++-
 testing/test_assertrewrite.py    | 5 +++++
 4 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 changelog/12300.bugfix.rst

diff --git a/AUTHORS b/AUTHORS
index 4619cf1bc..54ed85fc7 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -441,6 +441,7 @@ Yao Xiao
 Yoav Caspi
 Yuliang Shao
 Yusuke Kadowaki
+Yutian Li
 Yuval Shimon
 Zac Hatfield-Dodds
 Zachary Kneupper
diff --git a/changelog/12300.bugfix.rst b/changelog/12300.bugfix.rst
new file mode 100644
index 000000000..6c1624820
--- /dev/null
+++ b/changelog/12300.bugfix.rst
@@ -0,0 +1 @@
+Fixed handling of 'Function not implemented' error under squashfuse_ll, which is a different way to say that the mountpoint is read-only.
diff --git a/src/_pytest/assertion/rewrite.py b/src/_pytest/assertion/rewrite.py
index b6f14aa92..3d5df0d6c 100644
--- a/src/_pytest/assertion/rewrite.py
+++ b/src/_pytest/assertion/rewrite.py
@@ -1171,7 +1171,10 @@ def try_makedirs(cache_dir: Path) -> bool:
         return False
     except OSError as e:
         # as of now, EROFS doesn't have an equivalent OSError-subclass
-        if e.errno == errno.EROFS:
+        #
+        # squashfuse_ll returns ENOSYS "OSError: [Errno 38] Function not
+        # implemented" for a read-only error
+        if e.errno in {errno.EROFS, errno.ENOSYS}:
             return False
         raise
     return True
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index bedf6e276..82c7055b9 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -1972,6 +1972,11 @@ def test_try_makedirs(monkeypatch, tmp_path: Path) -> None:
     monkeypatch.setattr(os, "makedirs", partial(fake_mkdir, exc=err))
     assert not try_makedirs(p)
 
+    err = OSError()
+    err.errno = errno.ENOSYS
+    monkeypatch.setattr(os, "makedirs", partial(fake_mkdir, exc=err))
+    assert not try_makedirs(p)
+
     # unhandled OSError should raise
     err = OSError()
     err.errno = errno.ECHILD