fix(ext/napi): napi_is_buffer tests for ArrayBufferView (#27956)

use correct type check

Fixes: #27951

Author: devsnek

ext/napi/node_api.rs

@@ -400,18 +400,8 @@ fn napi_is_buffer(
   check_arg!(env, value);
   check_arg!(env, result);
 
-  let buffer_constructor =
-    v8::Local::new(&mut env.scope(), &env.buffer_constructor);
-
-  let Some(is_buffer) = value
-    .unwrap()
-    .instance_of(&mut env.scope(), buffer_constructor.into())
-  else {
-    return napi_set_last_error(env, napi_generic_failure);
-  };
-
   unsafe {
-    *result = is_buffer;
+    *result = value.unwrap().is_array_buffer_view();
   }
 
   napi_clear_last_error(env)

tests/napi/src/typedarray.rs

@@ -144,10 +144,26 @@ extern "C" fn test_external(
   typedarray
 }
 
+extern "C" fn test_is_buffer(
+  env: napi_env,
+  info: napi_callback_info,
+) -> napi_value {
+  let (args, argc, _) = napi_get_callback_info!(env, info, 1);
+  assert_eq!(argc, 1);
+
+  let mut is_buffer: bool = false;
+  assert_napi_ok!(napi_is_buffer(env, args[0], &mut is_buffer));
+
+  let mut result: napi_value = std::ptr::null_mut();
+  assert_napi_ok!(napi_get_boolean(env, is_buffer, &mut result));
+  result
+}
+
 pub fn init(env: napi_env, exports: napi_value) {
   let properties = &[
     napi_new_property!(env, "test_external", test_external),
     napi_new_property!(env, "test_multiply", test_multiply),
+    napi_new_property!(env, "test_is_buffer", test_is_buffer),
   ];
 
   assert_napi_ok!(napi_define_properties(

tests/napi/typedarray_test.js

@@ -1,5 +1,6 @@
 // Copyright 2018-2025 the Deno authors. MIT license.
 
+import { Buffer } from "node:buffer";
 import { assert, assertEquals, loadTestLibrary } from "./common.js";
 
 const typedarray = loadTestLibrary();
@@ -28,6 +29,14 @@ Deno.test("napi typedarray float64", function () {
   assertEquals(Math.round(10 * doubleResult[2]) / 10, -6.6);
 });
 
+Deno.test("napi_is_buffer", () => {
+  assert(!typedarray.test_is_buffer(5));
+  assert(!typedarray.test_is_buffer([]));
+  assert(typedarray.test_is_buffer(new Uint8Array()));
+  assert(typedarray.test_is_buffer(new Uint32Array()));
+  assert(typedarray.test_is_buffer(new Buffer([])));
+});
+
 // TODO(bartlomieju): this test causes segfaults when used with jemalloc.
 // Node documentation provides a hint that this function is not supported by
 // other runtime like electron.