Remove file-locking in MH.pack() method.

This change looks massive but it's mostly a re-indenting after
removing some try...finally blocks.

Also adds a test case that does a pack() while the mailbox is locked; this
test would have turned up bugs in the original code on some platforms.

In both nmh and GNU Mailutils' implementation of MH-format mailboxes,
no locking is done of individual message files when renaming them.

The original mailbox.py code did do locking, which meant that message
files had to be opened.  This code was buggy on certain platforms
(found through reading the code); there were code paths that closed
the file object and then called _unlock_file() on it.

Will backport to 25-maint once I see how the buildbots react to this patch.

diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index c6b0fa00e3c13087f27b72c83c299e05878d200c..108d874fe09ea7c35948c5667b8aece223894da3 100755 (executable)
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -1054,27 +1054,13 @@ class MH(Mailbox):
         for key in self.iterkeys():
             if key - 1 != prev:
                 changes.append((key, prev + 1))
-                f = open(os.path.join(self._path, str(key)), 'r+')
-                try:
-                    if self._locked:
-                        _lock_file(f)
-                    try:
-                        if hasattr(os, 'link'):
-                            os.link(os.path.join(self._path, str(key)),
-                                    os.path.join(self._path, str(prev + 1)))
-                            if sys.platform == 'os2emx':
-                                # cannot unlink an open file on OS/2
-                                f.close()
-                            os.unlink(os.path.join(self._path, str(key)))
-                        else:
-                            f.close()
-                            os.rename(os.path.join(self._path, str(key)),
-                                      os.path.join(self._path, str(prev + 1)))
-                    finally:
-                        if self._locked:
-                            _unlock_file(f)
-                finally:
-                    f.close()
+                if hasattr(os, 'link'):
+                    os.link(os.path.join(self._path, str(key)),
+                            os.path.join(self._path, str(prev + 1)))
+                    os.unlink(os.path.join(self._path, str(key)))
+                else:
+                    os.rename(os.path.join(self._path, str(key)),
+                              os.path.join(self._path, str(prev + 1)))
             prev += 1
         self._next_key = prev + 1
         if len(changes) == 0:

diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index 2434dbc47f4dfbbdfae3f2c482de08dacd968556..97270d005129d4ba6aa5563cc447b246efeab18c 100644 (file)
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -887,6 +887,21 @@ class TestMH(TestMailbox):
         self.assert_(self._box.get_sequences() ==
                      {'foo':[1, 2, 3], 'unseen':[1], 'bar':[3], 'replied':[3]})
 
+        # Test case for packing while holding the mailbox locked.
+        key0 = self._box.add(msg1)
+        key1 = self._box.add(msg1)
+        key2 = self._box.add(msg1)
+        key3 = self._box.add(msg1)
+
+        self._box.remove(key0)
+        self._box.remove(key2)
+        self._box.lock()
+        self._box.pack()
+        self._box.unlock()
+        self.assert_(self._box.get_sequences() ==
+                     {'foo':[1, 2, 3, 4, 5],
+                      'unseen':[1], 'bar':[3], 'replied':[3]})
+        
     def _get_lock_path(self):
         return os.path.join(self._path, '.mh_sequences.lock')