#1693546: don't add quotes around RFC 2231 encoded values.

The RFC is bit hard to understand on this point, but the examples
clearly show that parameter values that are encoded according
to its charset/language rules don't have surrounding quotes, and
the ABNF does not allow for quotes.  So when we produce such
encoded values, we no longer add quotes.

Lib/email/message.py

@@ -66,17 +66,19 @@ def _formatparam(param, value=None, quote=True):
     if value is not None and len(value) > 0:
         # A tuple is used for RFC 2231 encoded parameter values where items
         # are (charset, language, value).  charset is a string, not a Charset
-        # instance.
+        # instance.  RFC 2231 encoded values are never quoted, per RFC.
         if isinstance(value, tuple):
             # Encode as per RFC 2231
             param += '*'
             value = utils.encode_rfc2231(value[2], value[0], value[1])
+            return '%s=%s' % (param, value)
         else:
             try:
                 value.encode('ascii')
             except UnicodeEncodeError:
                 param += '*'
                 value = utils.encode_rfc2231(value, 'utf-8', '')
+                return '%s=%s' % (param, value)
         # BAW: Please check this.  I think that if quote is set it should
         # force quoting even if not necessary.
         if quote or tspecials.search(value):

Lib/email/test/test_email.py

@@ -534,7 +534,7 @@ class TestMessageAPI(TestEmailBase):
         msg.add_header('Content-Disposition', 'attachment',
             filename="Fußballer.ppt")
         self.assertEqual(
-            'attachment; filename*="utf-8\'\'Fu%C3%9Fballer.ppt"',
+            'attachment; filename*=utf-8\'\'Fu%C3%9Fballer.ppt',
             msg['Content-Disposition'])
 
     def test_nonascii_add_header_via_triple(self):
@@ -542,7 +542,23 @@ class TestMessageAPI(TestEmailBase):
         msg.add_header('Content-Disposition', 'attachment',
             filename=('iso-8859-1', '', 'Fußballer.ppt'))
         self.assertEqual(
-            'attachment; filename*="iso-8859-1\'\'Fu%DFballer.ppt"',
+            'attachment; filename*=iso-8859-1\'\'Fu%DFballer.ppt',
+            msg['Content-Disposition'])
+
+    def test_ascii_add_header_with_tspecial(self):
+        msg = Message()
+        msg.add_header('Content-Disposition', 'attachment',
+            filename="windows [filename].ppt")
+        self.assertEqual(
+            'attachment; filename="windows [filename].ppt"',
+            msg['Content-Disposition'])
+
+    def test_nonascii_add_header_with_tspecial(self):
+        msg = Message()
+        msg.add_header('Content-Disposition', 'attachment',
+            filename="Fußballer [filename].ppt")
+        self.assertEqual(
+            "attachment; filename*=utf-8''Fu%C3%9Fballer%20%5Bfilename%5D.ppt",
             msg['Content-Disposition'])
 
 
@@ -3643,7 +3659,7 @@ To: bbb@zzz.org
 Subject: This is a test message
 Date: Fri, 4 May 2001 14:05:44 -0400
 Content-Type: text/plain; charset=us-ascii;
- title*="us-ascii'en'This%20is%20even%20more%20%2A%2A%2Afun%2A%2A%2A%20isn%27t%20it%21"
+ title*=us-ascii'en'This%20is%20even%20more%20%2A%2A%2Afun%2A%2A%2A%20isn%27t%20it%21
 
 
 Hi,
@@ -3673,7 +3689,7 @@ To: bbb@zzz.org
 Subject: This is a test message
 Date: Fri, 4 May 2001 14:05:44 -0400
 Content-Type: text/plain; charset="us-ascii";
- title*="us-ascii'en'This%20is%20even%20more%20%2A%2A%2Afun%2A%2A%2A%20isn%27t%20it%21"
+ title*=us-ascii'en'This%20is%20even%20more%20%2A%2A%2Afun%2A%2A%2A%20isn%27t%20it%21
 
 
 Hi,
@@ -3688,6 +3704,32 @@ Do you like this message?
         msg = self._msgobj('msg_32.txt')
         eq(msg.get_content_charset(), 'us-ascii')
 
+    def test_rfc2231_parse_rfc_quoting(self):
+        m = textwrap.dedent('''\
+            Content-Disposition: inline;
+            \tfilename*0*=''This%20is%20even%20more%20;
+            \tfilename*1*=%2A%2A%2Afun%2A%2A%2A%20;
+            \tfilename*2="is it not.pdf"
+
+            ''')
+        msg = email.message_from_string(m)
+        self.assertEqual(msg.get_filename(),
+                         'This is even more ***fun*** is it not.pdf')
+        self.assertEqual(m, msg.as_string())
+
+    def test_rfc2231_parse_extra_quoting(self):
+        m = textwrap.dedent('''\
+            Content-Disposition: inline;
+            \tfilename*0*="''This%20is%20even%20more%20";
+            \tfilename*1*="%2A%2A%2Afun%2A%2A%2A%20";
+            \tfilename*2="is it not.pdf"
+
+            ''')
+        msg = email.message_from_string(m)
+        self.assertEqual(msg.get_filename(),
+                         'This is even more ***fun*** is it not.pdf')
+        self.assertEqual(m, msg.as_string())
+
     def test_rfc2231_no_language_or_charset(self):
         m = '''\
 Content-Transfer-Encoding: 8bit

Misc/NEWS

@@ -11,6 +11,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #1693546: fix email.message RFC 2231 parameter encoding to be in better
+  compliance (no "s around encoded values).
+
 - Improved the diff message in the unittest module's assertCountEqual().
 
 - Issue #1155362: email.utils.parsedate_tz now handles a missing space before