Issue 7970: When email.Parser.Parser parses a MIME message of type

message/rfc822 it turns it into an object whose body consists of
a list containing a single Message object.  HeaderParser, on the
other hand, just copies the body as a string.  Generator.flatten
has a special handler for the message mime type that expected the
body to be the one item list.  This fails if the message was parsed
by HeaderParser.  So we now check to see if the body is a string
first, and if so just we just emit it.

Lib/email/generator.py

@@ -276,8 +276,16 @@ class Generator:
         # of length 1.  The zeroth element of the list should be the Message
         # object for the subpart.  Extract that object, stringify it, and
         # write it out.
-        g.flatten(msg.get_payload(0), unixfrom=False)
-        self._fp.write(s.getvalue())
+        # Except, it turns out, when it's a string instead, which happens when
+        # and only when HeaderParser is used on a message of mime type
+        # message/rfc822.  Such messages are generated by, for example,
+        # Groupwise when forwarding unadorned messages.  (Issue 7970.)  So
+        # in that case we just emit the string body.
+        payload = msg.get_payload()
+        if isinstance(payload, list):
+            g.flatten(msg.get_payload(0), unixfrom=False)
+            payload = s.getvalue()
+        self._fp.write(payload)
 
 
 

Lib/email/test/data/msg_46.txt

+Return-Path: <sender@example.net>
+Delivery-Date: Mon, 08 Feb 2010 14:05:16 +0100
+Received: from example.org (example.org [64.5.53.58])
+    by example.net (node=mxbap2) with ESMTP (Nemesis)
+    id UNIQUE for someone@example.com; Mon, 08 Feb 2010 14:05:16 +0100
+Date: Mon, 01 Feb 2010 12:21:16 +0100
+From: "Sender" <sender@example.net>
+To: <someone@example.com>
+Subject: GroupwiseForwardingTest
+Mime-Version: 1.0
+Content-Type: message/rfc822
+
+Return-path: <sender@example.net>
+Message-ID: <4B66B890.4070408@teconcept.de>
+Date: Mon, 01 Feb 2010 12:18:40 +0100
+From: "Dr. Sender" <sender@example.net>
+MIME-Version: 1.0
+To: "Recipient" <recipient@example.com>
+Subject: GroupwiseForwardingTest
+Content-Type: text/plain; charset=ISO-8859-15
+Content-Transfer-Encoding: 7bit
+
+Testing email forwarding with Groupwise 1.2.2010

Lib/email/test/test_email.py

@@ -179,6 +179,18 @@ class TestMessageAPI(TestEmailBase):
         self.assertRaises(Errors.HeaderParseError,
                           msg.set_boundary, 'BOUNDARY')
 
+    def test_message_rfc822_only(self):
+        # Issue 7970: message/rfc822 not in multipart parsed by
+        # HeaderParser caused an exception when flattened.
+        fp = openfile(findfile('msg_46.txt'))
+        msgdata = fp.read()
+        parser = email.Parser.HeaderParser()
+        msg = parser.parsestr(msgdata)
+        out = StringIO()
+        gen = email.Generator.Generator(out, True, 0)
+        gen.flatten(msg, False)
+        self.assertEqual(out.getvalue(), msgdata)
+
     def test_get_decoded_payload(self):
         eq = self.assertEqual
         msg = self._msgobj('msg_10.txt')

Misc/NEWS

@@ -15,6 +15,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #7970: email.Generator.flatten now correctly flattens message/rfc822
+  messages parsed by email.Parser.HeaderParser.
+
 - Issue #3426: ``os.path.abspath`` now returns unicode when its arg is unicode.
 
 - Issue #7633: In the decimal module, Context class methods (with the