[3.12] gh-120930: Remove extra blank occuring in wrapped encoded words in email headers (GH-121747) (GH-121964)

gh-120930: Remove extra blank occuring in wrapped encoded words in email headers (GH-121747)
(cherry picked from commit cecacee)

Co-authored-by: Matthieu Caneill <matthieucan@users.noreply.github.com>

Author: miss-islington

Lib/email/_header_value_parser.py

@@ -2988,6 +2988,7 @@ def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset,
             excess = len(encoded_word) - remaining_space
         lines[-1] += encoded_word
         to_encode = to_encode[len(to_encode_word):]
+        leading_whitespace = ''
 
         if to_encode:
             lines.append(' ')

Lib/test/test_email/test_generator.py

@@ -294,6 +294,19 @@ def test_defaults_handle_spaces_between_encoded_words_when_folded(self):
         g.flatten(msg)
         self.assertEqual(s.getvalue(), expected)
 
+    def test_defaults_handle_spaces_when_encoded_words_is_folded_in_middle(self):
+        source = ('A very long long long long long long long long long long long long '
+                  'long long long long long long long long long long long súmmäry')
+        expected = ('Subject: A very long long long long long long long long long long long long\n'
+                    ' long long long long long long long long long long long =?utf-8?q?s=C3=BAmm?=\n'
+                    ' =?utf-8?q?=C3=A4ry?=\n\n').encode('ascii')
+        msg = EmailMessage()
+        msg['Subject'] = source
+        s = io.BytesIO()
+        g = BytesGenerator(s)
+        g.flatten(msg)
+        self.assertEqual(s.getvalue(), expected)
+
     def test_defaults_handle_spaces_at_start_of_subject(self):
         source = " Уведомление"
         expected = b"Subject:  =?utf-8?b?0KPQstC10LTQvtC80LvQtdC90LjQtQ==?=\n\n"

Misc/NEWS.d/next/Library/2024-07-14-11-18-28.gh-issue-120930.Kuo4L0.rst

@@ -0,0 +1,2 @@
+Fixed a bug introduced by gh-92081 that added an incorrect extra
+blank to encoded words occurring in wrapped headers.