feat: Pure JS custom host objects

Avoids substantial slowdown caused by host objects with embedder fields.

* Depends on: denoland/rusty_v8#1322
* Depends on: denoland/rusty_v8#1324
* Deno bug: denoland/deno#12067

core/01_core.js

@@ -800,6 +800,14 @@ for (let i = 0; i < 10; i++) {
  op_shutdown: shutdown,
  } = ensureFastOps();
 
+ const hostObjectBrand = SymbolFor("Deno.core.hostObject");
+
+ function createHostObject() {
+ const o = ObjectCreate(null);
+ o[hostObjectBrand] = hostObjectBrand;
+ return o;
+ }
+
  // Extra Deno.core.* exports
  const core = ObjectAssign(globalThis.Deno.core, {
  asyncStub,
@@ -842,7 +850,8 @@ for (let i = 0; i < 10; i++) {
  source,
  specifier,
  ) => ops.op_eval_context(source, specifier),
- createHostObject: () => ops.op_create_host_object(),
+ createHostObject,
+ hostObjectBrand,
  encode: (text) => ops.op_encode(text),
  decode: (buffer) => ops.op_decode(buffer),
  serialize: (

core/ops_builtin.rs

@@ -57,7 +57,6 @@ crate::extension!(
  ops_builtin_v8::op_set_has_tick_scheduled,
  ops_builtin_v8::op_eval_context,
  ops_builtin_v8::op_queue_microtask,
- ops_builtin_v8::op_create_host_object,
  ops_builtin_v8::op_encode,
  ops_builtin_v8::op_decode,
  ops_builtin_v8::op_serialize,

core/ops_builtin_v8.rs

@@ -132,15 +132,6 @@ pub fn op_queue_microtask(
  scope.enqueue_microtask(cb);
 }
 
-#[op2(core)]
-pub fn op_create_host_object<'a>(
- scope: &mut v8::HandleScope<'a>,
-) -> v8::Local<'a, v8::Object> {
- let template = v8::ObjectTemplate::new(scope);
- template.set_internal_field_count(1);
- template.new_instance(scope).unwrap()
-}
-
 #[op2(core)]
 pub fn op_encode<'a>(
  scope: &mut v8::HandleScope<'a>,
@@ -254,6 +245,23 @@ impl<'a> v8::ValueSerializerImpl for SerializeDeserialize<'a> {
  }
  }
 
+ fn has_custom_host_object(
+ &mut self,
+ _scope: &mut v8::HandleScope,
+ ) -> bool {
+ true
+ }
+
+ fn is_host_object<'s>(
+ &mut self,
+ scope: &mut v8::HandleScope<'s>,
+ object: v8::Local<'s, v8::Object>,
+ ) -> Option<bool> {
+ let key = v8::String::new(scope, "Deno.core.hostObject").unwrap();
+ let symbol = v8::Symbol::for_key(scope, key);
+ object.has_own_property(scope, symbol.into())
+ }
+
  fn write_host_object<'s>(
  &mut self,
  scope: &mut v8::HandleScope<'s>,