https://github.com/python/cpython/commit/7dc2f33a07a9073a50c11464bfba312813bc3a6a
commit: 7dc2f33a07a9073a50c11464bfba312813bc3a6a
branch: 3.15
author: Miss Islington (bot) <[email protected]>
committer: bitdancer <[email protected]>
date: 2026-10-09T15:35:44-04:00
summary:

[3.15] gh-87720 Fix additional header refolding-quoting edge case (GH-134271) 
(#159069)

In this case, the higher level syntactic unit fit on the remainder of
the line in un-encoded format, and that higher level unit was
not a ptext or vtext, so the encoding check failed.  To fix this, we
look inside the current unit to see if has anything that was
originally encoded.
(cherry picked from commit 5a22a62b96a68c2dd31784c5e3427ad7b365388a)

Co-authored-by: R. David Murray <[email protected]>

files:
A Misc/NEWS.d/next/Library/2026-10-08-16-18-43.gh-issue-87720.Elqdl9.rst
M Lib/email/_header_value_parser.py
M Lib/test/test_email/test__header_value_parser.py

diff --git a/Lib/email/_header_value_parser.py 
b/Lib/email/_header_value_parser.py
index 792072ab9f6128..ee8bd23adba8a3 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -166,6 +166,14 @@ def comments(self):
             comments.extend(token.comments)
         return comments
 
+    def contains_token_type(self, *token_types):
+        if self.token_type in token_types:
+            return True
+        for t in self:
+            if t.contains_token_type(*token_types):
+                return True
+        return False
+
     def fold(self, *, policy):
         return _refold_parse_tree(self, policy=policy)
 
@@ -933,6 +941,9 @@ def pop_trailing_ws(self):
     def comments(self):
         return []
 
+    def contains_token_type(self, *token_types):
+        return self.token_type in token_types
+
     def __getnewargs__(self):
         return(str(self), self.token_type)
 
@@ -2916,7 +2927,7 @@ def _refold_with_ew(parse_tree, lines, maxlen, encoding, 
*, policy):
             continue
         tstr = str(part)
         if not want_encoding:
-            if part.token_type in ('ptext', 'vtext'):
+            if part.token_type == 'ptext' or part.contains_token_type('vtext'):
                 # Encode if tstr contains special characters.
                 want_encoding = not SPECIALSNL.isdisjoint(tstr)
             else:
diff --git a/Lib/test/test_email/test__header_value_parser.py 
b/Lib/test/test_email/test__header_value_parser.py
index 9d9fe418ee4d06..26e9249ba9e948 100644
--- a/Lib/test/test_email/test__header_value_parser.py
+++ b/Lib/test/test_email/test__header_value_parser.py
@@ -3336,6 +3336,11 @@ def 
test_address_list_with_specials_in_encoded_word(self):
              'A =?utf-8?q?v=C3=A9ry?= long name\n'
              ' containing =?utf-8?q?a=2C?= comma\n'
              ' <[email protected]>\n'),
+            ('=?utf-8?Q?a=2C=20123456789012345678901234567890123456?='
+                ' <[email protected]>',
+             '=?utf-8?q?a=2C?=\n'
+             ' 123456789012345678901234567890123456\n'
+             ' <[email protected]>\n'),
         ]
         for (to, folded) in cases:
             with self.subTest(to=to):
diff --git 
a/Misc/NEWS.d/next/Library/2026-10-08-16-18-43.gh-issue-87720.Elqdl9.rst 
b/Misc/NEWS.d/next/Library/2026-10-08-16-18-43.gh-issue-87720.Elqdl9.rst
new file mode 100644
index 00000000000000..a2df7654b31444
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-08-16-18-43.gh-issue-87720.Elqdl9.rst
@@ -0,0 +1,3 @@
+Fixed error in :mod:`email` new policies where header folding failed to
+detect the need to re-quote text obtained from encoded words in certain
+cases.

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