gh-69602-html5-encoding-alias

Doc/library/codecs.rst

@@ -1310,7 +1310,7 @@ particular, the following variants typically exist:
 |                 |                                |                                |
 |                 |                                | .. versionadded:: 3.5          |
 +-----------------+--------------------------------+--------------------------------+
-| mac_cyrillic    | maccyrillic                    | Belarusian, Bulgarian,         |
+| mac_cyrillic    | maccyrillic, x-mac-cyrillic    | Belarusian, Bulgarian,         |
 |                 |                                | Macedonian, Russian, Serbian   |
 +-----------------+--------------------------------+--------------------------------+
 | mac_greek       | macgreek                       | Greek                          |

Lib/encodings/aliases.py

@@ -502,6 +502,7 @@
 
     # mac_cyrillic codec
     'maccyrillic'        : 'mac_cyrillic',
+    'x_mac_cyrillic'     : 'mac_cyrillic',
 
     # mac_greek codec
     'macgreek'           : 'mac_greek',

Lib/test/test_codecs.py

@@ -2247,6 +2247,15 @@ def test_basic(self):
 
 
 class BasicUnicodeTest(unittest.TestCase, MixInCheckStateHandling):
+    def test_html5_aliases(self):
+        for alias, encoding in (
+            ('windows-874', 'cp874'),
+            ('x-mac-cyrillic', 'mac_cyrillic'),
+        ):
+            with self.subTest(alias=alias):
+                self.assertEqual(codecs.lookup(alias).name,
+                                 codecs.lookup(encoding).name)
+
     def test_basics(self):
         s = "abc123"  # all codecs should be able to encode these
         for encoding in all_unicode_encodings:

Misc/NEWS.d/next/Library/2026-09-20-15-14-50.gh-issue-69602.Fk3mQ9.rst

@@ -0,0 +1 @@
+Add ``x-mac-cyrillic`` as an alias for the ``mac_cyrillic`` codec.