feat: add ObjectTemplate::set_immutable_proto() (#977)

This commit exposes SetImmutableProto().

src/binding.cc

@@ -1122,6 +1122,10 @@ void v8__ObjectTemplate__SetAccessorProperty(const v8::ObjectTemplate& self,
       ptr_to_local(&key), ptr_to_local(&getter), ptr_to_local(&setter), attr);
 }
 
+void v8__ObjectTemplate__SetImmutableProto(const v8::ObjectTemplate& self) {
+  return ptr_to_local(&self)->SetImmutableProto();
+}
+
 const v8::Object* v8__Object__New(v8::Isolate* isolate) {
   return local_to_ptr(v8::Object::New(isolate));
 }

src/template.rs

@@ -100,6 +100,7 @@ extern "C" {
     setter: *const FunctionTemplate,
     attr: PropertyAttribute,
   );
+  fn v8__ObjectTemplate__SetImmutableProto(this: *const ObjectTemplate);
 }
 
 impl Template {
@@ -362,4 +363,10 @@ impl ObjectTemplate {
       )
     }
   }
+
+  /// Makes the ObjectTemplate for an immutable prototype exotic object,
+  /// with an immutable proto.
+  pub fn set_immutable_proto(&self) {
+    unsafe { v8__ObjectTemplate__SetImmutableProto(self) };
+  }
 }

tests/test_api.rs

@@ -1456,6 +1456,36 @@ fn object_template_from_function_template() {
   }
 }
 
+#[test]
+fn object_template_immutable_proto() {
+  let _setup_guard = setup();
+  let isolate = &mut v8::Isolate::new(Default::default());
+  {
+    let scope = &mut v8::HandleScope::new(isolate);
+    let object_templ = v8::ObjectTemplate::new(scope);
+    object_templ.set_immutable_proto();
+    let context = v8::Context::new_from_template(scope, object_templ);
+    let scope = &mut v8::ContextScope::new(scope, context);
+    let source = r#"
+      {
+        let r = 0;
+
+        try {
+          Object.setPrototypeOf(globalThis, {});
+        } catch {
+          r = 42;
+        }
+
+        String(r);
+      }
+    "#;
+    let actual = eval(scope, source).unwrap();
+    let expected = v8::String::new(scope, "42").unwrap();
+
+    assert!(actual == expected);
+  }
+}
+
 #[test]
 fn function_template_signature() {
   let _setup_guard = setup();