From 2304a695f5c6cea9054863ea229aa0cbd82103c6 Mon Sep 17 00:00:00 2001
From: Aaron O'Mullan <aaron.omullan@gmail.com>
Date: Mon, 4 Oct 2021 15:39:32 +0200
Subject: [PATCH] perf(webidl): optimize createRecordConverter() (#12286)

Cuts self-time by ~6x, 172ns/iter => 22ns/iter benched on 1M Response builds / HeadersInit calls
---
 ext/webidl/00_webidl.js | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/ext/webidl/00_webidl.js b/ext/webidl/00_webidl.js
index 08de5aba6605f..1bf9d776f4f2b 100644
--- a/ext/webidl/00_webidl.js
+++ b/ext/webidl/00_webidl.js
@@ -9,6 +9,7 @@
 "use strict";
 
 ((window) => {
+  const core = window.Deno.core;
   const {
     ArrayBuffer,
     ArrayBufferIsView,
@@ -48,6 +49,7 @@
     ObjectGetOwnPropertyDescriptor,
     ObjectGetOwnPropertyDescriptors,
     ObjectGetPrototypeOf,
+    ObjectPrototypeHasOwnProperty,
     ObjectIs,
     PromisePrototypeThen,
     PromiseReject,
@@ -844,8 +846,21 @@
           opts,
         );
       }
-      const keys = ReflectOwnKeys(V);
       const result = {};
+      // Fast path for common case (not a Proxy)
+      if (!core.isProxy(V)) {
+        for (const key in V) {
+          if (!ObjectPrototypeHasOwnProperty(V, key)) {
+            continue;
+          }
+          const typedKey = keyConverter(key, opts);
+          const value = V[key];
+          const typedValue = valueConverter(value, opts);
+          result[typedKey] = typedValue;
+        }
+      }
+      // Slow path if Proxy (e.g: in WPT tests)
+      const keys = ReflectOwnKeys(V);
       for (const key of keys) {
         const desc = ObjectGetOwnPropertyDescriptor(V, key);
         if (desc !== undefined && desc.enumerable === true) {