From 9261a722c999e9f8b07cb9f7ac70c7d9c62dac07 Mon Sep 17 00:00:00 2001
From: Michael Anthony Leon <fbmal7@fb.com>
Date: Thu, 11 Nov 2021 18:48:30 -0800
Subject: [PATCH] Implement Object.hasOwn

Summary: Implement `hasOwn` according to the language specs [here](https://tc39.es/proposal-accessible-object-hasownproperty/).

Reviewed By: avp

Differential Revision: D32287266

fbshipit-source-id: 22a8520adfa09a193696a68459c475005a29b752
---
 include/hermes/VM/NativeFunctions.def   |  1 +
 include/hermes/VM/PredefinedStrings.def |  1 +
 lib/VM/JSLib/Object.cpp                 | 64 ++++++++++++++++++-------
 test/hermes/object-functions.js         | 33 +++++++++++++
 4 files changed, 81 insertions(+), 18 deletions(-)

diff --git a/include/hermes/VM/NativeFunctions.def b/include/hermes/VM/NativeFunctions.def
index 2716f7feaa9..68cc54e5b0e 100644
--- a/include/hermes/VM/NativeFunctions.def
+++ b/include/hermes/VM/NativeFunctions.def
@@ -203,6 +203,7 @@ NATIVE_FUNCTION(objectGetOwnPropertyDescriptors)
 NATIVE_FUNCTION(objectGetOwnPropertyNames)
 NATIVE_FUNCTION(objectGetOwnPropertySymbols)
 NATIVE_FUNCTION(objectGetPrototypeOf)
+NATIVE_FUNCTION(objectHasOwn)
 NATIVE_FUNCTION(objectIs)
 NATIVE_FUNCTION(objectIsExtensible)
 NATIVE_FUNCTION(objectIsFrozen)
diff --git a/include/hermes/VM/PredefinedStrings.def b/include/hermes/VM/PredefinedStrings.def
index ee7b3683889..23cb244ce1f 100644
--- a/include/hermes/VM/PredefinedStrings.def
+++ b/include/hermes/VM/PredefinedStrings.def
@@ -31,6 +31,7 @@ STR(toString, "toString")
 STR(description, "description")
 STR(toLocaleString, "toLocaleString")
 STR(hasOwnProperty, "hasOwnProperty")
+STR(hasOwn, "hasOwn")
 STR(isPrototypeOf, "isPrototypeOf")
 STR(propertyIsEnumerable, "propertyIsEnumerable")
 STR(valueOf, "valueOf")
diff --git a/lib/VM/JSLib/Object.cpp b/lib/VM/JSLib/Object.cpp
index 263e04b3a31..4c3862142f6 100644
--- a/lib/VM/JSLib/Object.cpp
+++ b/lib/VM/JSLib/Object.cpp
@@ -160,6 +160,13 @@ Handle<JSObject> createObjectConstructor(Runtime *runtime) {
       ctx,
       objectGetOwnPropertySymbols,
       1);
+  defineMethod(
+      runtime,
+      cons,
+      Predefined::getSymbolID(Predefined::hasOwn),
+      ctx,
+      objectHasOwn,
+      1);
   defineMethod(
       runtime,
       cons,
@@ -1262,24 +1269,8 @@ objectPrototypeValueOf(void *, Runtime *runtime, NativeArgs args) {
   return res;
 }
 
-/// ES11.0 19.1.3.2
-CallResult<HermesValue>
-objectPrototypeHasOwnProperty(void *, Runtime *runtime, NativeArgs args) {
-  /// 1. Let P be ? ToPropertyKey(V).
-  auto PRes = toPropertyKey(runtime, args.getArgHandle(0));
-  if (LLVM_UNLIKELY(PRes == ExecutionStatus::EXCEPTION)) {
-    return ExecutionStatus::EXCEPTION;
-  }
-  Handle<> P = *PRes;
-
-  /// 2. Let O be ? ToObject(this value).
-  auto ORes = toObject(runtime, args.getThisHandle());
-  if (LLVM_UNLIKELY(ORes == ExecutionStatus::EXCEPTION)) {
-    return ExecutionStatus::EXCEPTION;
-  }
-  Handle<JSObject> O = runtime->makeHandle<JSObject>(ORes.getValue());
-
-  /// 3. Return ? HasOwnProperty(O, P).
+static CallResult<HermesValue>
+objectHasOwnHelper(Runtime *runtime, Handle<JSObject> O, Handle<> P) {
   ComputedPropertyDescriptor desc;
   MutableHandle<SymbolID> tmpPropNameStorage{runtime};
   CallResult<bool> hasProp = JSObject::getOwnComputedDescriptor(
@@ -1306,6 +1297,43 @@ objectPrototypeHasOwnProperty(void *, Runtime *runtime, NativeArgs args) {
   return HermesValue::encodeBoolValue(false);
 }
 
+/// ES11.0 19.1.3.2
+CallResult<HermesValue>
+objectPrototypeHasOwnProperty(void *, Runtime *runtime, NativeArgs args) {
+  /// 1. Let P be ? ToPropertyKey(V).
+  auto PRes = toPropertyKey(runtime, args.getArgHandle(0));
+  if (LLVM_UNLIKELY(PRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+
+  /// 2. Let O be ? ToObject(this value).
+  auto ORes = toObject(runtime, args.getThisHandle());
+  if (LLVM_UNLIKELY(ORes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  /// 3. Return ? HasOwnProperty(O, P).
+  Handle<JSObject> O = runtime->makeHandle<JSObject>(ORes.getValue());
+  return objectHasOwnHelper(runtime, O, *PRes);
+}
+
+CallResult<HermesValue>
+objectHasOwn(void *, Runtime *runtime, NativeArgs args) {
+  /// 1. Let O be ? ToObject(O).
+  auto ORes = toObject(runtime, args.getArgHandle(0));
+  if (LLVM_UNLIKELY(ORes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  Handle<JSObject> O = runtime->makeHandle<JSObject>(ORes.getValue());
+
+  /// 2. Let P be ? ToPropertyKey(P).
+  auto PRes = toPropertyKey(runtime, args.getArgHandle(1));
+  if (LLVM_UNLIKELY(PRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  /// 3. Return ? HasOwnProperty(O, P).
+  return objectHasOwnHelper(runtime, O, *PRes);
+}
+
 CallResult<HermesValue>
 objectPrototypeIsPrototypeOf(void *, Runtime *runtime, NativeArgs args) {
   if (LLVM_UNLIKELY(!args.getArg(0).isObject())) {
diff --git a/test/hermes/object-functions.js b/test/hermes/object-functions.js
index 55a82ab7562..a3615c74aa6 100644
--- a/test/hermes/object-functions.js
+++ b/test/hermes/object-functions.js
@@ -175,6 +175,39 @@ try {
 }
 //CHECK: to_prim
 
+print('hasOwn');
+// CHECK-LABEL: hasOwn
+var obj = new Object();
+obj.prop = 'exists';
+
+function changeO() {
+  obj.newprop = obj.prop;
+  delete obj.prop;
+}
+
+print(Object.hasOwn(obj, 'prop'));
+//CHECK: true
+changeO();
+print(Object.hasOwn(obj, 'prop'));
+//CHECK: false
+print(Object.hasOwn(obj, 'newprop'));
+//CHECK: true
+print(Object.hasOwn(obj, 'new' + 'prop'));
+//CHECK: true
+obj[5] = 'exists';
+print(Object.hasOwn(obj, 5));
+//CHECK: true
+print(Object.hasOwn([1, 2], 0));
+//CHECK: true
+print(Object.hasOwn([1, 2], 2));
+//CHECK: false
+
+var child = Object.create(obj);
+print(Object.hasOwn(child, 'newprop'));
+//CHECK: false
+print(Object.hasOwn(child, 5));
+//CHECK: false
+
 print('defineProperties');
 // CHECK-LABEL: defineProperties
 var a = [];