python · serhiy-storchaka · Jan 10, 2024 · Dec 26, 2023
@@ -1141,10 +1141,24 @@ def __len__(self):
        """Return a count of messages in the mailbox."""
        return len(list(self.iterkeys()))

+    def _open_mh_sequences_file(self, text):
+        mode = '' if text else 'b'
+        kwargs = {'encoding': 'ASCII'} if text else {}
+        path = os.path.join(self._path, '.mh_sequences')
+        while True:
+            try:
+                return open(path, 'r+' + mode, **kwargs)
+            except FileNotFoundError:
+                pass
+            try:
+                return open(path, 'x+' + mode, **kwargs)
+            except FileExistsError:
+                pass
+
    def lock(self):
        """Lock the mailbox."""
        if not self._locked:
-            self._file = open(os.path.join(self._path, '.mh_sequences'), 'rb+')
+            self._file = self._open_mh_sequences_file(text=False)
            _lock_file(self._file)
            self._locked = True

@@ -1225,8 +1239,9 @@ def get_sequences(self):

    def set_sequences(self, sequences):
        """Set sequences using the given name-to-key-list dictionary."""
-        f = open(os.path.join(self._path, '.mh_sequences'), 'w', encoding='ASCII')
+        f = self._open_mh_sequences_file(text=True)
        try:
+            os.close(os.open(f.name, os.O_WRONLY | os.O_TRUNC))
            for name, keys in sequences.items():
                if len(keys) == 0:
                    continue

@@ -1360,6 +1360,15 @@ def test_no_dot_mh_sequences_file(self):
        box.set_sequences({})
        self.assertEqual(os.listdir(path), ['.mh_sequences'])

+    def test_lock_unlock_no_dot_mh_sequences_file(self):
+        path = os.path.join(self._path, 'foo.bar')
+        os.mkdir(path)
+        box = self._factory(path)
+        self.assertEqual(os.listdir(path), [])
+        box.lock()
+        box.unlock()
+        self.assertEqual(os.listdir(path), ['.mh_sequences'])
+
    def test_issue2625(self):
        msg0 = mailbox.MHMessage(self._template % 0)
        msg0.add_sequence('foo')