From 7ea928c452e2baaa929e5a078d796ece3720e765 Mon Sep 17 00:00:00 2001
From: "Andrew M. Kuchling" <amk@amk.ca>
Date: Fri, 10 Nov 2006 13:15:58 +0000
Subject: [PATCH] [Patch #1514543] mailbox (Maildir): avoid losing messages on
 name clash

Two changes:

Where possible, use link()/remove() to move files into a directory; this
makes it easier to avoid overwriting an existing file.

Use _create_carefully() to create files in tmp/, which uses O_EXCL.
---
 Lib/mailbox.py | 27 ++++++++++++++++++++++-----
 Misc/NEWS      |  4 ++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 51c2ccc80f5..c6b0fa00e3c 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -255,7 +255,19 @@ class Maildir(Mailbox):
             suffix = ''
         uniq = os.path.basename(tmp_file.name).split(self.colon)[0]
         dest = os.path.join(self._path, subdir, uniq + suffix)
-        os.rename(tmp_file.name, dest)
+        try:
+            if hasattr(os, 'link'):
+                os.link(tmp_file.name, dest)
+                os.remove(tmp_file.name)
+            else:
+                os.rename(tmp_file.name, dest)
+        except OSError, e:
+            os.remove(tmp_file.name)
+            if e.errno == errno.EEXIST:
+                raise ExternalClashError('Name clash with existing message: %s'
+                                         % dest)
+            else:
+                raise
         if isinstance(message, MaildirMessage):
             os.utime(dest, (os.path.getatime(dest), message.get_date()))
         return uniq
@@ -431,12 +443,17 @@ class Maildir(Mailbox):
         except OSError, e:
             if e.errno == errno.ENOENT:
                 Maildir._count += 1
-                return open(path, 'wb+')
+                try:
+                    return _create_carefully(path)
+                except OSError, e:
+                    if e.errno != errno.EEXIST:
+                        raise
             else:
                 raise
-        else:
-            raise ExternalClashError('Name clash prevented file creation: %s' %
-                                     path)
+
+        # Fall through to here if stat succeeded or open raised EEXIST.
+        raise ExternalClashError('Name clash prevented file creation: %s' %
+                                 path)
 
     def _refresh(self):
         """Update table of contents mapping."""
diff --git a/Misc/NEWS b/Misc/NEWS
index d91e64dbc53..d41d7cc30f0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -140,6 +140,10 @@ Library
 - Bug #1575506: mailbox.py: Single-file mailboxes didn't re-lock
   properly in their flush() method.
 
+- Patch #1514543: mailbox.py: In the Maildir class, report errors if there's 
+  a filename clash instead of possibly losing a message.  (Patch by David
+  Watson.)
+
 - Patch #1514544: mailbox.py: Try to ensure that messages/indexes have
   been physically written to disk after calling .flush() or
   .close(). (Patch by David Watson.)