gh-160306: Fix iso2022_jp_3 decoding of the JIS X 0213:2000 plane 2 mapping

Lib/test/test_multibytecodec.py

@@ -416,6 +416,23 @@ def test_streamwriter_strwrite(self):
         self.assertEqual(s.getvalue(), b'abcd')
 
 class Test_ISO2022(unittest.TestCase):
+    def test_jisx0213_plane2_mapping(self):
+        encoded = b'\x1b$(P};\x1b(B'
+        for encoding, char in (('iso2022_jp_3', '\u9b1d'),
+                               ('iso2022_jp_2004', '\u9b1c')):
+            with self.subTest(encoding=encoding):
+                self.assertEqual(char.encode(encoding), encoded)
+                self.assertEqual(encoded.decode(encoding), char)
+                self.assertEqual(char.encode(encoding).decode(encoding), char)
+                for split in range(len(encoded) + 1):
+                    with self.subTest(split=split):
+                        decoder = codecs.getincrementaldecoder(encoding)()
+                        decoded = decoder.decode(encoded[:split])
+                        decoded += decoder.decode(encoded[split:], final=True)
+                        self.assertEqual(decoded, char)
+                reader = codecs.getreader(encoding)(io.BytesIO(encoded))
+                self.assertEqual(reader.read(), char)
+
     def test_g2(self):
         iso2022jp2 = b'\x1b(B:hu4:unit\x1b.A\x1bNi de famille'
         uni = ':hu4:unit\xe9 de famille'

Misc/NEWS.d/next/Library/2026-10-26-21-20-00.gh-issue-160306.h7Lq2v.rst

@@ -0,0 +1,2 @@
+Fix the :mod:`!iso2022_jp_3` codec decoding the JIS X 0213:2000 plane 2
+character at row 93, cell 27 as U+9B1C instead of U+9B1D.

Modules/cjkcodecs/_codecs_iso2022.c

@@ -727,7 +727,7 @@ jisx0213_2000_2_decoder(const MultibyteCodec *codec, const unsigned char *data)
 {
     Py_UCS4 u;
     EMULATE_JISX0213_2000_DECODE_PLANE2_CHAR(config, u, data[0], data[1])
-    if (TRYMAP_DEC_ST(jisx0213_2_bmp, u, data[0], data[1]))
+    else if (TRYMAP_DEC_ST(jisx0213_2_bmp, u, data[0], data[1]))
         ;
     else if (TRYMAP_DEC_ST(jisx0213_2_emp, u, data[0], data[1]))
         u |= 0x20000;