gh-53144: Improve charset support in the email package (GH-149942)

Defer to the codecs module for all aliases.
Use MIME/IANA names for all IANA registered charsets.
Fix email.contentmanager.set_text_content().

diff --git a/Lib/email/charset.py b/Lib/email/charset.py
index c4b246455f86c64a281ec222b3eb07e7408d60bd..5981791820e740c2181331b0f786f3def99af373 100644 (file)
--- a/Lib/email/charset.py
+++ b/Lib/email/charset.py
@@ -9,6 +9,7 @@ __all__ = [
     'add_codec',
     ]
 
+import codecs
 from functools import partial
 
 import email.base64mime
@@ -58,37 +59,71 @@ CHARSETS = {
     'shift_jis':   (BASE64,    None,    'iso-2022-jp'),
     'iso-2022-jp': (BASE64,    None,    None),
     'koi8-r':      (BASE64,    BASE64,  None),
-    'utf-8':       (SHORTEST,  BASE64, 'utf-8'),
     }
 
-# Aliases for other commonly-used names for character sets.  Map
-# them to the real ones used in email.
+# Map Python codec names to their corresponding MIME/IANA names.
 ALIASES = {
-    'latin_1': 'iso-8859-1',
-    'latin-1': 'iso-8859-1',
-    'latin_2': 'iso-8859-2',
-    'latin-2': 'iso-8859-2',
-    'latin_3': 'iso-8859-3',
-    'latin-3': 'iso-8859-3',
-    'latin_4': 'iso-8859-4',
-    'latin-4': 'iso-8859-4',
-    'latin_5': 'iso-8859-9',
-    'latin-5': 'iso-8859-9',
-    'latin_6': 'iso-8859-10',
-    'latin-6': 'iso-8859-10',
-    'latin_7': 'iso-8859-13',
-    'latin-7': 'iso-8859-13',
-    'latin_8': 'iso-8859-14',
-    'latin-8': 'iso-8859-14',
-    'latin_9': 'iso-8859-15',
-    'latin-9': 'iso-8859-15',
-    'latin_10':'iso-8859-16',
-    'latin-10':'iso-8859-16',
-    'cp949':   'ks_c_5601-1987',
-    'euc_jp':  'euc-jp',
-    'euc_kr':  'euc-kr',
-    'ascii':   'us-ascii',
-    }
+    'ascii': 'us-ascii',
+    'big5hkscs': 'big5-hkscs',
+    'cp037': 'ibm037',
+    'cp1026': 'ibm1026',
+    'cp1140': 'ibm01140',
+    'cp1250': 'windows-1250',
+    'cp1251': 'windows-1251',
+    'cp1252': 'windows-1252',
+    'cp1253': 'windows-1253',
+    'cp1254': 'windows-1254',
+    'cp1255': 'windows-1255',
+    'cp1256': 'windows-1256',
+    'cp1257': 'windows-1257',
+    'cp1258': 'windows-1258',
+    'cp273': 'ibm273',
+    'cp424': 'ibm424',
+    'cp437': 'ibm437',
+    'cp500': 'ibm500',
+    'cp775': 'ibm775',
+    'cp850': 'ibm850',
+    'cp852': 'ibm852',
+    'cp855': 'ibm855',
+    'cp857': 'ibm857',
+    'cp858': 'ibm00858',
+    'cp860': 'ibm860',
+    'cp861': 'ibm861',
+    'cp862': 'ibm862',
+    'cp863': 'ibm863',
+    'cp864': 'ibm864',
+    'cp865': 'ibm865',
+    'cp866': 'ibm866',
+    'cp869': 'ibm869',
+    'cp874': 'windows-874',
+    'euc_jp': 'euc-jp',
+    'euc_kr': 'euc-kr',
+    'hz': 'hz-gb-2312',
+    'iso2022_jp': 'iso-2022-jp',
+    'iso2022_jp_2': 'iso-2022-jp-2',
+    'iso2022_kr': 'iso-2022-kr',
+    'iso8859-1': 'iso-8859-1',
+    'iso8859-10': 'iso-8859-10',
+    'iso8859-11': 'iso-8859-11',
+    'iso8859-13': 'iso-8859-13',
+    'iso8859-14': 'iso-8859-14',
+    'iso8859-15': 'iso-8859-15',
+    'iso8859-16': 'iso-8859-16',
+    'iso8859-2': 'iso-8859-2',
+    'iso8859-3': 'iso-8859-3',
+    'iso8859-4': 'iso-8859-4',
+    'iso8859-5': 'iso-8859-5',
+    'iso8859-6': 'iso-8859-6',
+    'iso8859-7': 'iso-8859-7',
+    'iso8859-8': 'iso-8859-8-i',
+    'iso8859-9': 'iso-8859-9',
+    'kz1048': 'kz-1048',
+    'mac-roman': 'macintosh',
+
+    # CP949 is not registered in IANA. KS_C_5601-1987 is not the same,
+    # but the closest registered option.
+    'cp949': 'ks_c_5601-1987',
+}
 
 
 # Map charsets to their Unicode codec strings.
@@ -215,7 +250,18 @@ class Charset:
             raise errors.CharsetError(input_charset)
         input_charset = input_charset.lower()
         # Set the input charset after filtering through the aliases
-        self.input_charset = ALIASES.get(input_charset, input_charset)
+        # For backward compatibility, try ALIASES first to let the user
+        # override it.
+        if input_charset in ALIASES:
+            input_charset = ALIASES[input_charset]
+        else:
+            try:
+                input_codec = codecs.lookup(input_charset).name
+            except LookupError:
+                pass
+            else:
+                input_charset = ALIASES.get(input_codec, input_codec)
+        self.input_charset = input_charset
         # We can try to guess which encoding and conversion to use by the
         # charset_map dictionary.  Try that first, but let the user override
         # it.

diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index 13fcb9787f1f32056cf9d0ed6c0452b2f710a470..faf2626bccce6519cd4354160c1802af37833da0 100644 (file)
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -173,11 +173,11 @@ def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
                      disposition=None, filename=None, cid=None,
                      params=None, headers=None):
     _prepare_set(msg, 'text', subtype, headers)
+
+    charset = email.charset.Charset(charset).input_charset
     cte, payload = _encode_text(string, charset, cte, msg.policy)
     msg.set_payload(payload)
-    msg.set_param('charset',
-                  email.charset.ALIASES.get(charset, charset),
-                  replace=True)
+    msg.set_param('charset', charset, replace=True)
     msg['Content-Transfer-Encoding'] = cte
     _finalize_set(msg, disposition, filename, cid, params)
 raw_data_manager.add_set_handler(str, set_text_content)

diff --git a/Lib/test/test_email/test_asian_codecs.py b/Lib/test/test_email/test_asian_codecs.py
index 85979ffd8169a753bd6842e55f32350dc27380dd..59013f087199e3a17fe6c59a376733cc1524c2f7 100644 (file)
--- a/Lib/test/test_email/test_asian_codecs.py
+++ b/Lib/test/test_email/test_asian_codecs.py
@@ -83,15 +83,15 @@ Japanese =?iso-2022-jp?b?GyRCRnxLXDhsGyhC?= =?iso-2022-jp?b?GyRCRnxLXDhsGyhC?=
         h.append(s, Charset('big5hkscs'))
         eq(h.encode(), """\
 Chinese =?gb2312?b?1tDOxA==?= =?gbk?b?1tDOxA==?= =?gb18030?b?1tDOxA==?=
- =?hz?b?fntWUE5Efn0=?= =?big5?b?pKSk5Q==?= =?big5hkscs?b?pKSk5Q==?=""")
+ =?hz-gb-2312?b?fntWUE5Efn0=?= =?big5?b?pKSk5Q==?= =?big5-hkscs?b?pKSk5Q==?=""")
         eq(decode_header(h.encode()),
            [(b'Chinese ', None),
             (b'\xd6\xd0\xce\xc4', 'gb2312'),
             (b'\xd6\xd0\xce\xc4', 'gbk'),
             (b'\xd6\xd0\xce\xc4', 'gb18030'),
-            (b'~{VPND~}', 'hz'),
+            (b'~{VPND~}', 'hz-gb-2312'),
             (b'\xa4\xa4\xa4\xe5', 'big5'),
-            (b'\xa4\xa4\xa4\xe5', 'big5hkscs'),
+            (b'\xa4\xa4\xa4\xe5', 'big5-hkscs'),
            ])
 
     def test_korean_codecs(self):

diff --git a/Lib/test/test_email/test_contentmanager.py b/Lib/test/test_email/test_contentmanager.py
index dceb54f15e48f4ebf8cad31ddff622c4a7f96ac6..bc0e5d3561815917c3a434d6eafcd53744880ac2 100644 (file)
--- a/Lib/test/test_email/test_contentmanager.py
+++ b/Lib/test/test_email/test_contentmanager.py
@@ -342,6 +342,19 @@ class TestRawDataManager(TestEmailBase):
         self.assertEqual(m.get_payload(decode=True).decode('utf-8'), content)
         self.assertEqual(m.get_content(), content)
 
+    def test_set_text_charset_cp949(self):
+        m = self._make_message()
+        content = "\ud55c\uad6d\uc5b4\n\uac02\n"
+        raw_data_manager.set_content(m, content, charset='cp949')
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="ks_c_5601-1987"
+            Content-Transfer-Encoding: base64
+
+            x9Gxub7uCoFBCg==
+            """))
+        self.assertEqual(m.get_payload(decode=True).decode('ks_c_5601-1987'), content)
+        self.assertEqual(m.get_content(), content)
+
     def test_set_text_plain_long_line_heuristics(self):
         m = self._make_message()
         content = ("Simple but long message that is over 78 characters"

diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index d2c2261edbe04e156a0bac2545ecffdde96168d4..19555d87085e176841ca1f688847c93d4795b505 100644 (file)
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -4970,6 +4970,128 @@ class TestCharset(unittest.TestCase):
         except KeyError:
             pass
 
+    def test_attributes(self):
+        from email import charset
+        c = Charset()
+        self.assertEqual(c.input_charset, 'us-ascii')
+        self.assertEqual(c.header_encoding, None)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'us-ascii')
+        self.assertEqual(c.input_codec, None)
+        self.assertEqual(c.output_codec, None)
+
+        c = Charset('us-ascii')
+        self.assertEqual(c.input_charset, 'us-ascii')
+        self.assertEqual(c.header_encoding, None)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'us-ascii')
+        self.assertEqual(c.input_codec, None)
+        self.assertEqual(c.output_codec, None)
+
+        c = Charset('utf8')
+        self.assertEqual(c.input_charset, 'utf-8')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'utf-8')
+        self.assertEqual(c.input_codec, 'utf-8')
+        self.assertEqual(c.output_codec, 'utf-8')
+
+        c = Charset('latin1')
+        self.assertEqual(c.input_charset, 'iso-8859-1')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'iso-8859-1')
+        self.assertEqual(c.input_codec, 'iso-8859-1')
+        self.assertEqual(c.output_codec, 'iso-8859-1')
+
+        c = Charset('latin9')
+        self.assertEqual(c.input_charset, 'iso-8859-15')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'iso-8859-15')
+        self.assertEqual(c.input_codec, 'iso-8859-15')
+        self.assertEqual(c.output_codec, 'iso-8859-15')
+
+        c = Charset('cyrillic')
+        self.assertEqual(c.input_charset, 'iso-8859-5')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'iso-8859-5')
+        self.assertEqual(c.input_codec, 'iso-8859-5')
+        self.assertEqual(c.output_codec, 'iso-8859-5')
+
+        c = Charset('cp1251')
+        self.assertEqual(c.input_charset, 'windows-1251')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'windows-1251')
+        self.assertEqual(c.input_codec, 'windows-1251')
+        self.assertEqual(c.output_codec, 'windows-1251')
+
+        c = Charset('cp1252')
+        self.assertEqual(c.input_charset, 'windows-1252')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'windows-1252')
+        self.assertEqual(c.input_codec, 'windows-1252')
+        self.assertEqual(c.output_codec, 'windows-1252')
+
+        c = Charset('eucjp')
+        self.assertEqual(c.input_charset, 'euc-jp')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'iso-2022-jp')
+        self.assertEqual(c.input_codec, 'euc-jp')
+        self.assertEqual(c.output_codec, 'iso-2022-jp')
+
+        c = Charset('cp949')
+        self.assertEqual(c.input_charset, 'ks_c_5601-1987')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'ks_c_5601-1987')
+        self.assertEqual(c.input_codec, 'ks_c_5601-1987')
+        self.assertEqual(c.output_codec, 'ks_c_5601-1987')
+
+        c = Charset('gb2312')
+        self.assertEqual(c.input_charset, 'gb2312')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'gb2312')
+        self.assertEqual(c.input_codec, 'gb2312')
+        self.assertEqual(c.output_codec, 'gb2312')
+
+        c = Charset('big5')
+        self.assertEqual(c.input_charset, 'big5')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'big5')
+        self.assertEqual(c.input_codec, 'big5')
+        self.assertEqual(c.output_codec, 'big5')
+
+    def test_user_charsets(self):
+        from email import charset
+        c = Charset('fake0')
+        self.assertEqual(c.input_charset, 'fake0')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'fake0')
+        self.assertEqual(c.input_codec, 'fake0')
+        self.assertEqual(c.output_codec, 'fake0')
+
+        charset.add_alias('fake1', 'mime-fake')
+        charset.add_alias('output-mime-fake', 'output-mime-fake-alias')
+        charset.add_codec('mime-fake', 'fakecodec')
+        charset.add_codec('output-mime-fake-alias', 'outputfakecodec')
+        charset.add_charset('mime-fake', charset.QP, None, 'output-mime-fake')
+
+        c = Charset('fake1')
+        self.assertEqual(c.input_charset, 'mime-fake')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'output-mime-fake-alias')
+        self.assertEqual(c.input_codec, 'fakecodec')
+        self.assertEqual(c.output_codec, 'outputfakecodec')
+
     def test_codec_encodeable(self):
         eq = self.assertEqual
         # Make sure us-ascii = no Unicode conversion
@@ -5010,6 +5132,11 @@ class TestCharset(unittest.TestCase):
         self.assertEqual(str(charset), 'us-ascii')
         self.assertRaises(errors.CharsetError, Charset, 'asc\xffii')
 
+    def test_bytes_charset_name(self):
+        charset = Charset(b'us-ascii')
+        self.assertEqual(str(charset), 'us-ascii')
+        self.assertRaises(errors.CharsetError, Charset, b'asc\xffii')
+
 
 
 # Test multilingual MIME headers.

diff --git a/Misc/NEWS.d/next/Library/2026-05-17-12-37-59.gh-issue-53144.c5tr1p.rst b/Misc/NEWS.d/next/Library/2026-05-17-12-37-59.gh-issue-53144.c5tr1p.rst
new file mode 100644 (file)
index 0000000..283a5ba
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-17-12-37-59.gh-issue-53144.c5tr1p.rst
@@ -0,0 +1,2 @@
+The :mod:`email` package now supports all aliases of Python codecs and uses
+MIME/IANA names for all IANA registered charsets.