gh-66515: mailbox.MH now supports folders withou the ".mh_sequences" file (GH-804)

(for example Claws Mail IMAP-cache folders).

1 files changed, 6 insertions, 3 deletions

diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 574c014..0e1d49b 100644
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -1198,7 +1198,11 @@ class MH(Mailbox):
     def get_sequences(self):
         """Return a name-to-key-list dictionary to define each sequence."""
         results = {}
-        with open(os.path.join(self._path, '.mh_sequences'), 'r', encoding='ASCII') as f:
+        try:
+            f = open(os.path.join(self._path, '.mh_sequences'), 'r', encoding='ASCII')
+        except FileNotFoundError:
+            return results
+        with f:
             all_keys = set(self.keys())
             for line in f:
                 try:
@@ -1221,9 +1225,8 @@ class MH(Mailbox):
 
     def set_sequences(self, sequences):
         """Set sequences using the given name-to-key-list dictionary."""
-        f = open(os.path.join(self._path, '.mh_sequences'), 'r+', encoding='ASCII')
+        f = open(os.path.join(self._path, '.mh_sequences'), 'w', encoding='ASCII')
         try:
-            os.close(os.open(f.name, os.O_WRONLY | os.O_TRUNC))
             for name, keys in sequences.items():
                 if len(keys) == 0:
                     continue