Raise when trying to acquire in R/O or missing folder

src/filelock/_soft.py

@@ -1,7 +1,11 @@
 import os
+import sys
+from errno import EACCES, ENOENT, EPERM
 
 from ._api import BaseFileLock
 
+PermissionError = PermissionError if sys.version_info[0] == 3 else OSError
+
 
 class SoftFileLock(BaseFileLock):
     """Simply watches the existence of the lock file."""
@@ -10,8 +14,11 @@ def _acquire(self):
         open_mode = os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_TRUNC
         try:
             fd = os.open(self._lock_file, open_mode)
-        except OSError:
-            pass
+        except OSError as exception:
+            if exception.errno in (EPERM, EACCES, ENOENT):
+                raise
+            if sys.platform == "win32" and not os.access(self._lock_file, os.W_OK):
+                raise PermissionError("Permission denied")
         else:
             self._lock_file_fd = fd
 

src/filelock/_windows.py

@@ -1,4 +1,5 @@
 import os
+from errno import EACCES, ENOENT, EPERM
 
 from ._api import BaseFileLock
 
@@ -15,8 +16,9 @@ def _acquire(self):
         open_mode = os.O_RDWR | os.O_CREAT | os.O_TRUNC
         try:
             fd = os.open(self._lock_file, open_mode)
-        except OSError:
-            pass
+        except OSError as exception:
+            if exception.errno in (EPERM, EACCES, ENOENT):
+                raise
         else:
             try:
                 msvcrt.locking(fd, msvcrt.LK_NBLCK, 1)

tests/test_filelock.py

@@ -3,11 +3,15 @@
 import logging
 import sys
 import threading
+from contextlib import contextmanager
+from stat import S_IWGRP, S_IWOTH, S_IWUSR
 
 import pytest
 
 from filelock import FileLock, SoftFileLock, Timeout
 
+PermissionError = PermissionError if sys.version_info[0] == 3 else OSError
+
 
 @pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
 def test_simple(lock_type, tmp_path, caplog):
@@ -29,6 +33,52 @@ def test_simple(lock_type, tmp_path, caplog):
     assert [r.levelno for r in caplog.records] == [logging.DEBUG, logging.DEBUG, logging.DEBUG, logging.DEBUG]
 
 
+@contextmanager
+def make_ro(path):
+    write = S_IWUSR | S_IWGRP | S_IWOTH
+    path.chmod(path.stat().st_mode & ~write)
+    yield
+    path.chmod(path.stat().st_mode | write)
+
+
+@pytest.fixture()
+def tmp_path_ro(tmp_path):
+    with make_ro(tmp_path):
+        yield tmp_path
+
+
+@pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
+@pytest.mark.skipif(sys.platform == "win32", reason="Windows does not have read only folders")
+def test_ro_folder(lock_type, tmp_path_ro):
+    lock = lock_type(str(tmp_path_ro / "a"))
+    with pytest.raises(PermissionError, match="Permission denied"):
+        lock.acquire()
+
+
+@pytest.fixture()
+def tmp_file_ro(tmp_path):
+    filename = tmp_path / "a"
+    filename.write_text("")
+    with make_ro(filename):
+        yield filename
+
+
+@pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
+def test_ro_file(lock_type, tmp_file_ro):
+    lock = lock_type(str(tmp_file_ro))
+    with pytest.raises(PermissionError, match="Permission denied"):
+        lock.acquire()
+
+
+@pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
+def test_missing_directory(lock_type, tmp_path_ro):
+    lock_path = tmp_path_ro / "a" / "b"
+    lock = lock_type(str(lock_path))
+
+    with pytest.raises(OSError, match="No such file or directory:"):
+        lock.acquire()
+
+
 @pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
 def test_nested_context_manager(lock_type, tmp_path):
     # lock is not released before the most outer with statement that locked the lock, is left

whitelist.txt

@@ -3,12 +3,18 @@ autodoc
 autosectionlabel
 caplog
 creat
+eacces
+enoent
+eperm
 exc
 fcntl
 filelock
 fmt
 intersphinx
 intervall
+iwgrp
+iwoth
+iwusr
 levelno
 lk
 lockfile
@@ -18,6 +24,7 @@ nitpicky
 param
 pygments
 rdwr
+ro
 skipif
 src
 tmp