n-api: add `napi_detach_arraybuffer`

As ArrayBuffer#detach is an ecma spec operation
([Section 24.1.1.3](https://tc39.es/ecma262/#sec-detacharraybuffer)),
it might be good to have it in N-API.

Fixes https://github.com/nodejs/node/issues/29674

PR-URL: https://github.com/nodejs/node/pull/29768
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>

2 files changed, 37 insertions, 0 deletions

diff --git a/test/js-native-api/test_typedarray/test.js b/test/js-native-api/test_typedarray/test.js
index 91e17ecbe8..5f51383254 100644
--- a/test/js-native-api/test_typedarray/test.js
+++ b/test/js-native-api/test_typedarray/test.js
@@ -74,3 +74,21 @@ nonByteArrayTypes.forEach((currentType) => {
     console.log(`start of offset ${currentType}`);
   }, RangeError);
 });
+
+// Test detaching
+arrayTypes.forEach((currentType) => {
+  const buffer = Reflect.construct(currentType, [8]);
+  assert.throws(
+    () => test_typedarray.Detach(buffer),
+    /A detachable arraybuffer was expected/);
+});
+{
+  const buffer = test_typedarray.External();
+  assert.ok(externalResult instanceof Int8Array);
+  assert.strictEqual(externalResult.length, 3);
+  assert.strictEqual(externalResult.byteLength, 3);
+  test_typedarray.Detach(buffer);
+  assert.ok(externalResult instanceof Int8Array);
+  assert.strictEqual(buffer.length, 0);
+  assert.strictEqual(buffer.byteLength, 0);
+}
diff --git a/test/js-native-api/test_typedarray/test_typedarray.c b/test/js-native-api/test_typedarray/test_typedarray.c
index 98480a4ea2..9d7d394fca 100644
--- a/test/js-native-api/test_typedarray/test_typedarray.c
+++ b/test/js-native-api/test_typedarray/test_typedarray.c
@@ -1,3 +1,4 @@
+#define NAPI_EXPERIMENTAL
 #include <js_native_api.h>
 #include <string.h>
 #include "../common.h"
@@ -165,12 +166,30 @@ static napi_value CreateTypedArray(napi_env env, napi_callback_info info) {
   return output_array;
 }
 
+static napi_value Detach(napi_env env, napi_callback_info info) {
+  size_t argc = 1;
+  napi_value args[1];
+  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));
+  NAPI_ASSERT(env, argc == 1, "Wrong number of arguments.");
+
+  bool is_typedarray;
+  NAPI_CALL(env, napi_is_typedarray(env, args[0], &is_typedarray));
+  NAPI_ASSERT(env, is_typedarray, "Wrong type of arguments. Expects a typedarray as first argument.");
+
+  napi_value arraybuffer;
+  NAPI_CALL(env, napi_get_typedarray_info(env, args[0], NULL, NULL, NULL, &arraybuffer, NULL));
+  NAPI_CALL(env, napi_detach_arraybuffer(env, arraybuffer));
+
+  return NULL;
+}
+
 EXTERN_C_START
 napi_value Init(napi_env env, napi_value exports) {
   napi_property_descriptor descriptors[] = {
     DECLARE_NAPI_PROPERTY("Multiply", Multiply),
     DECLARE_NAPI_PROPERTY("External", External),
     DECLARE_NAPI_PROPERTY("CreateTypedArray", CreateTypedArray),
+    DECLARE_NAPI_PROPERTY("Detach", Detach),
   };
 
   NAPI_CALL(env, napi_define_properties(