From f2dc25826f25e590472d41dc94fe7d6185f4c405 Mon Sep 17 00:00:00 2001
From: RedYetiDev <38299977+RedYetiDev@users.noreply.github.com>
Date: Thu, 26 Sep 2024 18:00:24 -0400
Subject: [PATCH] buffer: correctly apply prototype to cloned `File` / `Blob`

---
 lib/internal/blob.js                         |  1 +
 lib/internal/file.js                         |  1 +
 test/parallel/test-structuredClone-global.js | 13 +++++++++++++
 3 files changed, 15 insertions(+)

diff --git a/lib/internal/blob.js b/lib/internal/blob.js
index 0c38cd02c4a944..bb9a7d043759d0 100644
--- a/lib/internal/blob.js
+++ b/lib/internal/blob.js
@@ -386,6 +386,7 @@ class Blob {
 }
 
 function TransferableBlob(handle, length, type = '') {
+  ObjectSetPrototypeOf(this, Blob.prototype);
   markTransferMode(this, true, false);
   this[kHandle] = handle;
   this[kType] = type;
diff --git a/lib/internal/file.js b/lib/internal/file.js
index 65fec6dfd0c627..46dc96fa1bc6aa 100644
--- a/lib/internal/file.js
+++ b/lib/internal/file.js
@@ -130,6 +130,7 @@ class File extends Blob {
 
 function TransferableFile(handle, length, type = '') {
   FunctionPrototypeApply(TransferableBlob, this, [handle, length, type]);
+  ObjectSetPrototypeOf(this, File.prototype);
 }
 
 ObjectSetPrototypeOf(TransferableFile.prototype, File.prototype);
diff --git a/test/parallel/test-structuredClone-global.js b/test/parallel/test-structuredClone-global.js
index 50fcf6047828a8..34b6abe32d3fcf 100644
--- a/test/parallel/test-structuredClone-global.js
+++ b/test/parallel/test-structuredClone-global.js
@@ -30,6 +30,19 @@ for (const StreamClass of [ReadableStream, WritableStream, TransformStream]) {
   assert.ok(extendedTransfer instanceof StreamClass);
 }
 
+for (const Transferrable of [File, Blob]) {
+  const a2 = Transferrable === File ? '' : {};
+  const original = new Transferrable([], a2);
+  const transfer = structuredClone(original);
+  assert.strictEqual(Object.getPrototypeOf(transfer), Transferrable.prototype);
+  assert.ok(transfer instanceof Transferrable);
+
+  const extendedOriginal = new (class extends Transferrable {})([], a2);
+  const extendedTransfer = structuredClone(extendedOriginal);
+  assert.strictEqual(Object.getPrototypeOf(extendedTransfer), Transferrable.prototype);
+  assert.ok(extendedTransfer instanceof Transferrable);
+}
+
 {
   // See: https://github.com/nodejs/node/issues/49940
   const cloned = structuredClone({}, {