From de25c81fd0860d0fb604d105534721d8b37a4abd Mon Sep 17 00:00:00 2001
From: Marcos Casagrande <marcos@denode.com>
Date: Mon, 2 Oct 2023 02:18:34 +0200
Subject: perf(ext/web): optimize DOMException (#20715)
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This PR optimizes `DOMException` constructor increasing performance of
all Web APIs that throw a `DOMException` (ie: `AbortSignal`)

**main**
```
cpu: 13th Gen Intel(R) Core(TM) i9-13900H
runtime: deno 1.37.1 (x86_64-unknown-linux-gnu)

new DOMException()            9.66 µs/iter     103,476.8   (8.47 µs … 942.71 µs)   9.62 µs  11.29 µs  14.04 µs
abort writeTextFileSync      16.45 µs/iter      60,775.5    (13.65 µs … 1.33 ms)  16.39 µs  20.59 µs  24.12 µs
abort readFile               16.25 µs/iter      61,542.2  (15.12 µs … 621.14 µs)  16.18 µs  19.59 µs  22.33 µs
```

**this PR**
```
cpu: 13th Gen Intel(R) Core(TM) i9-13900H
runtime: deno 1.37.1 (x86_64-unknown-linux-gnu)

benchmark                    time (avg)        iter/s             (min … max)       p75       p99      p995
----------------------------------------------------------------------------- -----------------------------
new DOMException()            2.37 µs/iter     421,657.0     (2.33 µs … 2.58 µs)   2.37 µs   2.58 µs   2.58 µs
abort writeTextFileSync        7.1 µs/iter     140,760.1     (6.94 µs … 7.68 µs)   7.13 µs   7.68 µs   7.68 µs
abort readFile                5.48 µs/iter     182,648.2      (5.3 µs … 5.69 µs)   5.56 µs   5.69 µs   5.69 µ
```

```js
Deno.bench("new DOMException()", () => {
  new DOMException();
});

Deno.bench("abort writeTextFileSync", () => {
  const ac = new AbortController();
  ac.abort();
  try {
    Deno.writeTextFileSync("/tmp/out", "x", { signal: ac.signal });
  } catch {}
});

Deno.bench("abort readFile", async () => {
  const ac = new AbortController();
  ac.abort();
  try {
    await Deno.readFile("/tmp/out", { signal: ac.signal });
  } catch {}
});
```
---
 ext/web/01_dom_exception.js | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

(limited to 'ext/web/01_dom_exception.js')

diff --git a/ext/web/01_dom_exception.js b/ext/web/01_dom_exception.js
index 31d2cdc29..54d47beaf 100644
--- a/ext/web/01_dom_exception.js
+++ b/ext/web/01_dom_exception.js
@@ -26,6 +26,7 @@ import { createFilteredInspectProxy } from "ext:deno_console/01_console.js";
 const _name = Symbol("name");
 const _message = Symbol("message");
 const _code = Symbol("code");
+const _error = Symbol("error");
 
 // Defined in WebIDL 4.3.
 // https://webidl.spec.whatwg.org/#idl-DOMException
@@ -111,21 +112,8 @@ class DOMException {
     this[_code] = code;
     this[webidl.brand] = webidl.brand;
 
-    const error = new Error(message);
-    error.name = "DOMException";
-    ObjectDefineProperty(this, "stack", {
-      value: error.stack,
-      writable: true,
-      configurable: true,
-    });
-
-    // `DOMException` isn't a native error, so `Error.prepareStackTrace()` is
-    // not called when accessing `.stack`, meaning our structured stack trace
-    // hack doesn't apply. This patches it in.
-    ObjectDefineProperty(this, "__callSiteEvals", {
-      value: ArrayPrototypeSlice(error.__callSiteEvals, 1),
-      configurable: true,
-    });
+    this[_error] = new Error(message);
+    this[_error].name = "DOMException";
   }
 
   get message() {
@@ -160,6 +148,26 @@ class DOMException {
   }
 }
 
+ObjectDefineProperty(DOMException.prototype, "stack", {
+  get() {
+    return this[_error].stack;
+  },
+  set(value) {
+    this[_error].stack = value;
+  },
+  configurable: true,
+});
+
+// `DOMException` isn't a native error, so `Error.prepareStackTrace()` is
+// not called when accessing `.stack`, meaning our structured stack trace
+// hack doesn't apply. This patches it in.
+ObjectDefineProperty(DOMException.prototype, "__callSiteEvals", {
+  get() {
+    return ArrayPrototypeSlice(this[_error].__callSiteEvals, 1);
+  },
+  configurable: true,
+});
+
 ObjectSetPrototypeOf(DOMException.prototype, ErrorPrototype);
 
 webidl.configurePrototype(DOMException);
-- 
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