feat(stickybits): fix sticky bits and add inheritable option

.github/workflows/test.yml

@@ -15,7 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         python: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
-        platform: [ubuntu-latest, macos-latest]
+        platform: [ubuntu-latest, macos-13] # intel mac only
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Checkout

src/shinny_filelock/_flockd.py

@@ -4,21 +4,28 @@
 
 
 @contextmanager
-def flocked(path, blocking=True, create_file=False, shared=False):
+def flocked(path, blocking=True, create_file=False, shared=False, inheritable=False):
     """
     :param path: file path
     :param blocking: blocking lock, default True
     :param create_file: create file if not exists, default False
     :param shared: shared lock, default False
+    :param inheritable: inherit lock after exec, default False
     """
     fd = -1
+    fd_flags = os.O_RDONLY | os.O_NOCTTY
+    fd_flags_with_create = fd_flags | os.O_CREAT
     try:
-        fd_flags = os.O_RDONLY | os.O_NOCTTY
-        if create_file:
-            fd_flags |= os.O_CREAT
-        fd = os.open(path, fd_flags)
+        # when stick bits set, os.O_CREAT will raise PermissionError
+        try:
+            fd = os.open(path, fd_flags_with_create if create_file else fd_flags)
+        except PermissionError:
+            # maybe file exists and sits in a directory with sticky bits
+            fd = os.open(path, fd_flags)
         if fd == -1:
             raise ValueError()
+        # default fd in non-inheritable. See PEP 446: https://peps.python.org/pep-0446/
+        os.set_inheritable(fd, inheritable)
         flags = fcntl.LOCK_SH if shared else fcntl.LOCK_EX
         if not blocking:
             flags |= fcntl.LOCK_NB

tests/test_flock.py

@@ -1,17 +1,20 @@
-# the inclusion of the tests module is not meant to offer best practices for
-# testing in general, but rather to support the `find_packages` example in
-# setup.py that excludes installing the "tests" package
+import subprocess
 import unittest
 
 from shinny_filelock import flocked
 
 from ._timeout import timeout
 
+local_path = "/tmp/shinny-filelock-test.lock"
+
 
 class TestSimple(unittest.TestCase):
 
+    def setUp(self):
+        self.addCleanup(subprocess.check_call, ["sudo", "rm", "-f", local_path])
+
     def test_non_blocking_lock(self):
-        local_path = "/tmp/test.lock"
+        # local_path = "/tmp/test.lock"
         with flocked(local_path, blocking=False, create_file=True):
             try:
                 with flocked(local_path, blocking=False, create_file=True):
@@ -20,7 +23,6 @@ def test_non_blocking_lock(self):
                 self.assertEqual(e.__class__, BlockingIOError)
 
     def test_blocking_lock(self):
-        local_path = "/tmp/test-block.lock"
         with flocked(local_path, blocking=True, create_file=True):
             try:
                 with timeout(2):
@@ -30,7 +32,6 @@ def test_blocking_lock(self):
                 self.assertEqual(e.__class__, TimeoutError)
 
     def test_blocking_with_non_blocking_lock(self):
-        local_path = "/tmp/test-mix.lock"
         with flocked(local_path, blocking=True, create_file=True):
             try:
                 with flocked(local_path, blocking=False, create_file=True):
@@ -39,13 +40,19 @@ def test_blocking_with_non_blocking_lock(self):
                 self.assertEqual(e.__class__, BlockingIOError)
 
     def test_file_not_exists(self):
-        local_path = "/tmp/test-not-exists.lock"
         try:
             with flocked(local_path, blocking=True):
                 pass
         except Exception as e:
             self.assertEqual(e.__class__, FileNotFoundError)
 
+    def test_lock_with_file_created_by_another_user(self):
+        # use sudo to create a file with sticky bits
+        with open(local_path, "w"):
+            subprocess.check_call(["sudo", "chown", "2222:3333", local_path])
+        with flocked(local_path, blocking=True, create_file=True):
+            pass
+
 
 if __name__ == '__main__':
     unittest.main()

tox.ini

@@ -44,3 +44,4 @@ commands =
 [flake8]
 exclude = .tox,*.egg,build,data
 select = E,W,F
+max-line-length = 120