[Bug #1569790] mailbox.Maildir.get_folder() loses factory information

Both the Maildir and MH classes had this bug; the patch fixes both classes
and adds a test.

Will backport to 25-maint.

Lib/mailbox.py

@@ -367,12 +367,14 @@ class Maildir(Mailbox):
 
     def get_folder(self, folder):
         """Return a Maildir instance for the named folder."""
-        return Maildir(os.path.join(self._path, '.' + folder), create=False)
+        return Maildir(os.path.join(self._path, '.' + folder),
+                       factory=self._factory,
+                       create=False)
 
     def add_folder(self, folder):
         """Create a folder and return a Maildir instance representing it."""
         path = os.path.join(self._path, '.' + folder)
-        result = Maildir(path)
+        result = Maildir(path, factory=self._factory)
         maildirfolder_path = os.path.join(path, 'maildirfolder')
         if not os.path.exists(maildirfolder_path):
             os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY))
@@ -944,11 +946,13 @@ class MH(Mailbox):
 
     def get_folder(self, folder):
         """Return an MH instance for the named folder."""
-        return MH(os.path.join(self._path, folder), create=False)
+        return MH(os.path.join(self._path, folder),
+                  factory=self._factory, create=False)
 
     def add_folder(self, folder):
         """Create a folder and return an MH instance representing it."""
-        return MH(os.path.join(self._path, folder))
+        return MH(os.path.join(self._path, folder),
+                  factory=self._factory)
 
     def remove_folder(self, folder):
         """Delete the named folder, which must be empty."""

Lib/test/test_mailbox.py

@@ -673,6 +673,19 @@ class TestMaildir(TestMailbox):
         self._box.lock()
         self._box.unlock()
 
+    def test_folder (self):
+        # Test for bug #1569790: verify that folders returned by .get_folder()
+        # use the same factory function.
+        def dummy_factory (s):
+            return None
+        box = self._factory(self._path, factory=dummy_factory)
+        folder = box.add_folder('folder1')
+        self.assert_(folder._factory is dummy_factory)
+        
+        folder1_alias = box.get_folder('folder1')
+        self.assert_(folder1_alias._factory is dummy_factory)
+
+        
 
 class _TestMboxMMDF(TestMailbox):
 
@@ -789,7 +802,11 @@ class TestMH(TestMailbox):
 
     def test_get_folder(self):
         # Open folders
-        self._box.add_folder('foo.bar')
+        def dummy_factory (s):
+            return None
+        self._box = self._factory(self._path, dummy_factory)
+        
+        new_folder = self._box.add_folder('foo.bar')
         folder0 = self._box.get_folder('foo.bar')
         folder0.add(self._template % 'bar')
         self.assert_(os.path.isdir(os.path.join(self._path, 'foo.bar')))
@@ -797,6 +814,11 @@ class TestMH(TestMailbox):
         self.assert_(folder1.get_string(folder1.keys()[0]) == \
                      self._template % 'bar')
 
+        # Test for bug #1569790: verify that folders returned by .get_folder()
+        # use the same factory function.
+        self.assert_(new_folder._factory is self._box._factory)
+        self.assert_(folder0._factory is self._box._factory)
+
     def test_add_and_remove_folders(self):
         # Delete folders
         self._box.add_folder('one')

Misc/NEWS

@@ -96,6 +96,10 @@ Core and builtins
 Library
 -------
 
+- Bug #1569790: mailbox.py: Maildir.get_folder() and MH.get_folder()
+  weren't passing the message factory on to newly created Maildir/MH
+  objects.
+
 - Patch #1592250: Add elidge argument to Tkinter.Text.search.
 
 - Patch #838546: Make terminal become controlling in pty.fork()