test: refactor testcases for surrogate codes

Since the readable web streams  already returns
USVString
The changes made to blob.js and consumers.js  are reverted
Test cases are added to check  surrogate to USVString conversion for
ReadablewebStreams Textdecoder and Blob

PR-URL: #40351
Fixes: #39804

lib/internal/blob.js

@@ -42,7 +42,6 @@ const {
 } = require('internal/util/types');
 
 const {
-  toUSVString,
   createDeferredPromise,
   customInspectSymbol: kInspect,
   emitExperimentalWarning,
@@ -317,8 +316,7 @@ class Blob {
       throw new ERR_INVALID_THIS('Blob');
 
     const dec = new TextDecoder();
-    const str = dec.decode(await this.arrayBuffer());
-    return toUSVString(str);
+    return dec.decode(await this.arrayBuffer());
   }
 
   /**

lib/stream/consumers.js

@@ -16,10 +16,6 @@ const {
   Buffer,
 } = require('buffer');
 
-const {
-  toUSVString
-} = require('internal/util');
-
 /**
  * @typedef {import('../internal/webstreams/readablestream').ReadableStream
  * } ReadableStream
@@ -70,7 +66,7 @@ async function text(stream) {
   // Flush the streaming TextDecoder so that any pending
   // incomplete multibyte characters are handled.
   str += dec.decode(undefined, { stream: false });
-  return toUSVString(str);
+  return str;
 }
 
 /**

test/parallel/test-blob.js

@@ -88,11 +88,11 @@ assert.throws(() => new Blob({}), {
 }
 
 {
-  const b = new Blob(['hello', Buffer.from('world\ud801')]);
-  assert.strictEqual(b.size, 13);
+  const b = new Blob(['hello', new Uint8Array([0xed,0xa0,0x88])]);
+  assert.strictEqual(b.size, 8);
   b.text().then(common.mustCall((text) => {
-    assert.strictEqual(text, 'helloworld\ufffd');
-    assert.strictEqual(text.length, 11);
+    assert.strictEqual(text, 'hello\ufffd\ufffd\ufffd');
+    assert.strictEqual(text.length, 8);
   }));
 }
 

test/parallel/test-whatwg-encoding-custom-textdecoder.js

@@ -191,3 +191,18 @@ if (common.hasIntl) {
     }
   );
 }
+
+// Test TextDecoder for surrogate code points
+{
+  const decoder = new TextDecoder();
+  const chunk = Buffer.from([0x66, 0x6f, 0x6f, 0xed, 0xa0, 0x80]); // foo + U+D800
+  const str = decoder.decode(chunk);
+  assert.strictEqual(str, 'foo\ufffd\ufffd\ufffd');
+}
+
+{
+  const decoder = new TextDecoder();
+  const chunk = Buffer.from('\ud807');
+  const str = decoder.decode(chunk);
+  assert.strictEqual(str, '\ufffd');
+}