lib: correct windows-1252 decoding in TextDecoder

lib/internal/encoding.js

@@ -28,7 +28,6 @@
 const kDecoder = Symbol('decoder');
 const kFatal = Symbol('kFatal');
 const kUTF8FastPath = Symbol('kUTF8FastPath');
-const kLatin1FastPath = Symbol('kLatin1FastPath');
 const kIgnoreBOM = Symbol('kIgnoreBOM');
 
 const {
@@ -55,7 +54,7 @@
   encodeIntoResults,
   encodeUtf8String,
   decodeUTF8,
   decodeLatin1,
 } = binding;
 
 const { Buffer } = require('buffer');
@@ -420,10 +419,9 @@
       this[kFatal] = Boolean(options?.fatal);
       // Only support fast path for UTF-8.
       this[kUTF8FastPath] = enc === 'utf-8';
-      this[kLatin1FastPath] = enc === 'windows-1252';
       this[kHandle] = undefined;
 
-      if (!this[kUTF8FastPath] && !this[kLatin1FastPath]) {
+      if (!this[kUTF8FastPath]) {
         this.#prepareConverter();
       }
     }
@@ -440,16 +438,11 @@
       validateDecoder(this);
 
       this[kUTF8FastPath] &&= !(options?.stream);
-      this[kLatin1FastPath] &&= !(options?.stream);
 
       if (this[kUTF8FastPath]) {
         return decodeUTF8(input, this[kIgnoreBOM], this[kFatal]);
       }
 
-      if (this[kLatin1FastPath]) {
-        return decodeLatin1(input, this[kIgnoreBOM], this[kFatal]);
-      }
-
       this.#prepareConverter();
 
       validateObject(options, 'options', kValidateObjectAllowObjectsAndNull);

test/parallel/test-whatwg-encoding-custom-windows-1252.js

@@ -0,0 +1,85 @@
+'use strict';
+
+// Tests for Windows-1252 encoding, specifically the 0x80-0x9F range
+// where it differs from ISO-8859-1 (Latin-1).
+// Refs: https://github.com/nodejs/node/issues/56542
+// Refs: https://encoding.spec.whatwg.org/#windows-1252
+
+require('../common');
+
+const assert = require('assert');
+
+// Test specific case from issue #56542
+{
+  const decoder = new TextDecoder('windows-1252');
+  const decoded = decoder.decode(new Uint8Array([0x92]));
+  assert.strictEqual(
+    decoded.charCodeAt(0),
+    0x2019,
+    'Byte 0x92 should decode to U+2019 (') not U+0092'
+  );
+  assert.strictEqual(decoded, '\u2019', 'Expected right single quotation mark');
+}
+
+// Test all 32 characters in the 0x80-0x9F range where Windows-1252
+// differs from ISO-8859-1. These mappings are defined by the WHATWG
+// Encoding Standard.
+// Source: https://encoding.spec.whatwg.org/#index-windows-1252
+{
+  const testCases = [
+    [0x80, 0x20AC, '€'],  // EURO SIGN
+    [0x81, 0x0081, '\u0081'],  // Undefined (maps to itself)
+    [0x82, 0x201A, '‚'],  // SINGLE LOW-9 QUOTATION MARK
+    [0x83, 0x0192, 'ƒ'],  // LATIN SMALL LETTER F WITH HOOK
+    [0x84, 0x201E, '„'],  // DOUBLE LOW-9 QUOTATION MARK
+    [0x85, 0x2026, '…'],  // HORIZONTAL ELLIPSIS
+    [0x86, 0x2020, '†'],  // DAGGER
+    [0x87, 0x2021, '‡'],  // DOUBLE DAGGER
+    [0x88, 0x02C6, 'ˆ'],  // MODIFIER LETTER CIRCUMFLEX ACCENT
+    [0x89, 0x2030, '‰'],  // PER MILLE SIGN
+    [0x8A, 0x0160, 'Š'],  // LATIN CAPITAL LETTER S WITH CARON
+    [0x8B, 0x2039, '‹'],  // SINGLE LEFT-POINTING ANGLE QUOTATION MARK
+    [0x8C, 0x0152, 'Œ'],  // LATIN CAPITAL LIGATURE OE
+    [0x8D, 0x008D, '\u008D'],  // Undefined (maps to itself)
+    [0x8E, 0x017D, 'Ž'],  // LATIN CAPITAL LETTER Z WITH CARON
+    [0x8F, 0x008F, '\u008F'],  // Undefined (maps to itself)
+    [0x90, 0x0090, '\u0090'],  // Undefined (maps to itself)
+    [0x91, 0x2018, '''],  // LEFT SINGLE QUOTATION MARK
+    [0x92, 0x2019, '''],  // RIGHT SINGLE QUOTATION MARK
+    [0x93, 0x201C, '"'],  // LEFT DOUBLE QUOTATION MARK
+    [0x94, 0x201D, '"'],  // RIGHT DOUBLE QUOTATION MARK
+    [0x95, 0x2022, '•'],  // BULLET
+    [0x96, 0x2013, '–'],  // EN DASH
+    [0x97, 0x2014, '—'],  // EM DASH
+    [0x98, 0x02DC, '˜'],  // SMALL TILDE
+    [0x99, 0x2122, '™'],  // TRADE MARK SIGN
+    [0x9A, 0x0161, 'š'],  // LATIN SMALL LETTER S WITH CARON
+    [0x9B, 0x203A, '›'],  // SINGLE RIGHT-POINTING ANGLE QUOTATION MARK
+    [0x9C, 0x0153, 'œ'],  // LATIN SMALL LIGATURE OE
+    [0x9D, 0x009D, '\u009D'],  // Undefined (maps to itself)
+    [0x9E, 0x017E, 'ž'],  // LATIN SMALL LETTER Z WITH CARON
+    [0x9F, 0x0178, 'Ÿ'],  // LATIN CAPITAL LETTER Y WITH DIAERESIS
+  ];
+
+  const decoder = new TextDecoder('windows-1252');
+
+  for (const [byte, expectedCodePoint, expectedChar] of testCases) {
+    const decoded = decoder.decode(new Uint8Array([byte]));
+    const actualCodePoint = decoded.charCodeAt(0);
+
+    assert.strictEqual(
+      actualCodePoint,
+      expectedCodePoint,
+      `Byte 0x${byte.toString(16).toUpperCase()} should decode to ` +
+      `U+${expectedCodePoint.toString(16).toUpperCase().padStart(4, '0')} ` +
+      `but got U+${actualCodePoint.toString(16).toUpperCase().padStart(4, '0')}`
+    );
+
+    assert.strictEqual(
+      decoded,
+      expectedChar,
+      `Byte 0x${byte.toString(16).toUpperCase()} should decode to ` +
+      `${expectedChar} but got ${decoded}`
+    );
+  }
+}