gh-118643: Fix AttributeError in the email module (GH-119099)

Fix regression introduced in gh-100884: AttributeError when re-fold a long
address list.

Also fix more cases of incorrect encoding of the address separator in the
address list missed in gh-100884.

Lib/email/_header_value_parser.py

@@ -956,6 +956,7 @@ class _InvalidEwError(errors.HeaderParseError):
 DOT = ValueTerminal('.', 'dot')
 ListSeparator = ValueTerminal(',', 'list-separator')
 ListSeparator.as_ew_allowed = False
+ListSeparator.syntactic_break = False
 RouteComponentMarker = ValueTerminal('@', 'route-component-marker')
 
 #
@@ -2844,7 +2845,9 @@ def _refold_parse_tree(parse_tree, *, policy):
             if not hasattr(part, 'encode'):
                 # It's not a Terminal, do each piece individually.
                 parts = list(part) + parts
-            else:
+                want_encoding = False
+                continue
+            elif part.as_ew_allowed:
                 # It's a terminal, wrap it as an encoded word, possibly
                 # combining it with previously encoded words if allowed.
                 if (last_ew is not None and
@@ -2858,8 +2861,14 @@ def _refold_parse_tree(parse_tree, *, policy):
                 # so clear it now.
                 leading_whitespace = ''
                 last_charset = charset
-            want_encoding = False
-            continue
+                want_encoding = False
+                continue
+            else:
+                # It's a terminal which should be kept non-encoded
+                # (e.g. a ListSeparator).
+                last_ew = None
+                want_encoding = False
+                # fall through
 
         if len(tstr) <= maxlen - len(lines[-1]):
             lines[-1] += tstr

Lib/test/test_email/test__header_value_parser.py

@@ -3077,9 +3077,17 @@ def test_address_list_with_unicode_names_in_quotes(self):
                 ' =?utf-8?q?bei=C3=9Ft_bei=C3=9Ft?= <biter@example.com>\n')
 
     def test_address_list_with_list_separator_after_fold(self):
-        to = '0123456789' * 8 + '@foo, ä <foo@bar>'
+        a = 'x' * 66 + '@example.com'
+        to = f'{a}, "Hübsch Kaktus" <beautiful@example.com>'
         self._test(parser.get_address_list(to)[0],
-                   '0123456789' * 8 + '@foo,\n =?utf-8?q?=C3=A4?= <foo@bar>\n')
+            f'{a},\n =?utf-8?q?H=C3=BCbsch?= Kaktus <beautiful@example.com>\n')
+
+        a = '.' * 79
+        to = f'"{a}" <xyz@example.com>, "Hübsch Kaktus" <beautiful@example.com>'
+        self._test(parser.get_address_list(to)[0],
+            f'{a}\n'
+            ' <xyz@example.com>, =?utf-8?q?H=C3=BCbsch?= Kaktus '
+            '<beautiful@example.com>\n')
 
     # XXX Need tests with comments on various sides of a unicode token,
     # and with unicode tokens in the comments.  Spaces inside the quotes

Misc/NEWS.d/next/Library/2024-05-16-17-31-46.gh-issue-118643.hAWH4C.rst

@@ -0,0 +1,2 @@
+Fix an AttributeError in the :mod:`email` module when re-fold a long address
+list. Also fix more cases of incorrect encoding of the address separator in the address list.