From bdccbbc8285acb60e34e5186c69cef100a4ee59e Mon Sep 17 00:00:00 2001
From: Meghan Denny <meghan@bun.sh>
Date: Tue, 11 Feb 2025 18:10:43 -0800
Subject: [PATCH] node: fix Buffer.from(arrayBuffer) (#17267)

---
 src/codegen/generate-classes.ts |  2 +-
 test/js/node/buffer.test.js     | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/codegen/generate-classes.ts b/src/codegen/generate-classes.ts
index 8d8f01be84..844a64c4c5 100644
--- a/src/codegen/generate-classes.ts
+++ b/src/codegen/generate-classes.ts
@@ -2281,7 +2281,7 @@ JSC_DEFINE_HOST_FUNCTION(Zig::jsFunctionInherits, (JSC::JSGlobalObject * globalO
     switch (id) {
 ${jsclasses
   .map(v => v[0])
-  .map((v, i) => `    case ${i}: return JSValue::encode(jsBoolean(cell->inherits<WebCore::JS${v}>()));`)
+  .map((v, i) => `    case ${i}: return JSValue::encode(jsBoolean(jsDynamicCast<WebCore::JS${v}*>(cell) != nullptr));`)
   .join("\n")}
     }
     return JSValue::encode(jsBoolean(false));
diff --git a/test/js/node/buffer.test.js b/test/js/node/buffer.test.js
index b19ae42cf2..8d5b2c27b3 100644
--- a/test/js/node/buffer.test.js
+++ b/test/js/node/buffer.test.js
@@ -2980,3 +2980,31 @@ it("should not trim utf-8 start bytes at end of string", () => {
   const buf2 = Buffer.from("36e1", "hex");
   expect(buf2.toString("utf-8")).toEqual("6\uFFFD");
 });
+
+it("Buffer.from(arrayBuffer)", () => {
+  const ab = Buffer.from([10, 11, 12, 13, 14, 15, 16, 17, 18, 19]).buffer;
+  const buf = Buffer.from(ab);
+  expect(buf.length).toBe(10);
+  expect(buf.buffer).toBe(ab);
+  expect(buf.byteOffset).toBe(0);
+  expect(buf.byteLength).toBe(10);
+  expect(buf[Symbol.iterator]().toArray()).toEqual([10, 11, 12, 13, 14, 15, 16, 17, 18, 19]);
+});
+it("Buffer.from(arrayBuffer, byteOffset)", () => {
+  const ab = Buffer.from([10, 11, 12, 13, 14, 15, 16, 17, 18, 19]).buffer;
+  const buf = Buffer.from(ab, 2);
+  expect(buf.length).toBe(8);
+  expect(buf.buffer).toBe(ab);
+  expect(buf.byteOffset).toBe(2);
+  expect(buf.byteLength).toBe(8);
+  expect(buf[Symbol.iterator]().toArray()).toEqual([12, 13, 14, 15, 16, 17, 18, 19]);
+});
+it("Buffer.from(arrayBuffer, byteOffset, length)", () => {
+  const ab = Buffer.from([10, 11, 12, 13, 14, 15, 16, 17, 18, 19]).buffer;
+  const buf = Buffer.from(ab, 3, 5);
+  expect(buf.length).toBe(5);
+  expect(buf.buffer).toBe(ab);
+  expect(buf.byteOffset).toBe(3);
+  expect(buf.byteLength).toBe(5);
+  expect(buf[Symbol.iterator]().toArray()).toEqual([13, 14, 15, 16, 17]);
+});