gh-153521: Preserve bytes message sets in imaplib (GH-153907)

Signed-off-by: cuishuang <imcusg@gmail.com>

Author: cuishuang

Lib/imaplib.py

@@ -168,6 +168,8 @@ def _seq_range(item):
 
 
 def _format_sequence_set(arg):
+    if isinstance(arg, (bytes, bytearray)):
+        return str(arg, 'ascii')
     if isinstance(arg, (int, str)):
         return str(arg)
     # A sequence of message numbers and ranges.

Lib/test/test_imaplib.py

@@ -292,6 +292,8 @@ def test_sequence_set(self):
         # A scalar is passed through as a string.
         self.assertEqual(m._sequence_set(5), '5')
         self.assertEqual(m._sequence_set('1:3,7'), '1:3,7')
+        self.assertEqual(m._sequence_set(b'1:3,7'), '1:3,7')
+        self.assertEqual(m._sequence_set(bytearray(b'1:3,7')), '1:3,7')
         # A sequence of numbers and ranges is formatted as a sequence set.
         self.assertEqual(m._sequence_set([1, 2, 5]), '1,2,5')
         self.assertEqual(m._sequence_set([1, (3, 5), (8, '*')]), '1,3:5,8:*')
@@ -333,6 +335,7 @@ def test_substitute(self):
                          r'(\Seen \Answered)')
         # '?s' formats a message sequence set.
         self.assertEqual(sub('?s', [[1, (3, 5), (8, '*')]]), '1,3:5,8:*')
+        self.assertEqual(sub('?s', [b'1:3,7']), '1:3,7')
         # '??' is a literal '?'.
         self.assertEqual(sub('a?? b', []), 'a? b')
 
@@ -1574,6 +1577,16 @@ def cmd_FETCH(self, tag, args):
         ])
         self.assertEqual(server.args, ['2:4', '(FLAGS)'])
 
+        # A preformatted message set may be passed as bytes.
+        typ, data = client.fetch(b'2:4', '(FLAGS)')
+        self.assertEqual(typ, 'OK')
+        self.assertEqual(data, [
+            br'2 (FLAGS (\Seen))',
+            br'3 (FLAGS (\Seen))',
+            br'4 (FLAGS (\Seen))',
+        ])
+        self.assertEqual(server.args, ['2:4', '(FLAGS)'])
+
         # A comma-separated set with an open range up to '*'.
         typ, data = client.fetch('1,3:*', '(FLAGS)')
         self.assertEqual(typ, 'OK')