string_decoder: Migrate to use internal/errors

PR-URL: https://github.com/nodejs/node/pull/14682
Refs: https://github.com/nodejs/node/issues/11273
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/string_decoder.js

@@ -23,6 +23,7 @@
 
 const Buffer = require('buffer').Buffer;
 const internalUtil = require('internal/util');
+const errors = require('internal/errors');
 const isEncoding = Buffer[internalUtil.kIsEncodingSymbol];
 
 // Do not cache `Buffer.isEncoding` when checking encoding names as some
@@ -31,7 +32,7 @@ function normalizeEncoding(enc) {
   const nenc = internalUtil.normalizeEncoding(enc);
   if (typeof nenc !== 'string' &&
       (Buffer.isEncoding === isEncoding || !Buffer.isEncoding(enc)))
-    throw new Error(`Unknown encoding: ${enc}`);
+    throw new errors.TypeError('ERR_UNKNOWN_ENCODING', enc);
   return nenc || enc;
 }
 

test/parallel/test-string-decoder.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const inspect = require('util').inspect;
 const StringDecoder = require('string_decoder').StringDecoder;
@@ -124,13 +124,23 @@ assert.strictEqual(decoder.write(Buffer.from('3DD8', 'hex')), '');
 assert.strictEqual(decoder.write(Buffer.from('4D', 'hex')), '');
 assert.strictEqual(decoder.end(), '\ud83d');
 
-assert.throws(() => {
-  new StringDecoder(1);
-}, /^Error: Unknown encoding: 1$/);
+common.expectsError(
+  () => new StringDecoder(1),
+  {
+    code: 'ERR_UNKNOWN_ENCODING',
+    type: TypeError,
+    message: 'Unknown encoding: 1'
+  }
+);
 
-assert.throws(() => {
-  new StringDecoder('test');
-}, /^Error: Unknown encoding: test$/);
+common.expectsError(
+  () => new StringDecoder('test'),
+  {
+    code: 'ERR_UNKNOWN_ENCODING',
+    type: TypeError,
+    message: 'Unknown encoding: test'
+  }
+);
 
 // test verifies that StringDecoder will correctly decode the given input
 // buffer with the given encoding to the expected output. It will attempt all