From b566d184fedcd0fae3de19a54adfa5ce09466cc1 Mon Sep 17 00:00:00 2001
From: Benjamin Gruenbaum <benjamingr@gmail.com>
Date: Mon, 7 Dec 2020 22:22:58 +0200
Subject: [PATCH] refactor(cli/rt): deduplicate code (#8649)

---
 cli/rt/01_web_util.js             |  4 +--
 cli/rt/99_main.js                 | 43 +++----------------------------
 cli/tests/034_onload/main.ts      |  3 +++
 docs/runtime/program_lifecycle.md |  3 ++-
 4 files changed, 10 insertions(+), 43 deletions(-)

diff --git a/cli/rt/01_web_util.js b/cli/rt/01_web_util.js
index 3076993ff3..a9573a71db 100644
--- a/cli/rt/01_web_util.js
+++ b/cli/rt/01_web_util.js
@@ -128,11 +128,11 @@
     wrappedHandler.handler = handler;
     return wrappedHandler;
   }
-  function defineEventHandler(emitter, name) {
+  function defineEventHandler(emitter, name, defaultValue = undefined) {
     // HTML specification section 8.1.5.1
     Object.defineProperty(emitter, `on${name}`, {
       get() {
-        return this[handlerSymbol]?.get(name)?.handler;
+        return this[handlerSymbol]?.get(name)?.handler ?? defaultValue;
       },
       set(value) {
         if (!this[handlerSymbol]) {
diff --git a/cli/rt/99_main.js b/cli/rt/99_main.js
index f582994c7f..40c9c636f5 100644
--- a/cli/rt/99_main.js
+++ b/cli/rt/99_main.js
@@ -31,6 +31,7 @@ delete Object.prototype.__proto__;
   const denoNs = window.__bootstrap.denoNs;
   const denoNsUnstable = window.__bootstrap.denoNsUnstable;
   const errors = window.__bootstrap.errors.errors;
+  const { defineEventHandler } = window.__bootstrap.webUtil;
 
   let windowIsClosing = false;
 
@@ -289,46 +290,8 @@ delete Object.prototype.__proto__;
     Object.setPrototypeOf(globalThis, Window.prototype);
     eventTarget.setEventTargetData(globalThis);
 
-    const handlerSymbol = Symbol("eventHandlers");
-
-    function makeWrappedHandler(handler) {
-      function wrappedHandler(...args) {
-        if (typeof wrappedHandler.handler !== "function") {
-          return;
-        }
-        return wrappedHandler.handler.call(this, ...args);
-      }
-      wrappedHandler.handler = handler;
-      return wrappedHandler;
-    }
-    // TODO(benjamingr) reuse when we can reuse code between web crates
-    // This function is very similar to `defineEventHandler` in `01_web_util.js`
-    // but it returns `null` instead of `undefined` is handler is not defined.
-    function defineEventHandler(emitter, name) {
-      // HTML specification section 8.1.5.1
-      Object.defineProperty(emitter, `on${name}`, {
-        get() {
-          return this[handlerSymbol]?.get(name)?.handler ?? null;
-        },
-        set(value) {
-          if (!this[handlerSymbol]) {
-            this[handlerSymbol] = new Map();
-          }
-          let handlerWrapper = this[handlerSymbol]?.get(name);
-          if (handlerWrapper) {
-            handlerWrapper.handler = value;
-          } else {
-            handlerWrapper = makeWrappedHandler(value);
-            this.addEventListener(name, handlerWrapper);
-          }
-          this[handlerSymbol].set(name, handlerWrapper);
-        },
-        configurable: true,
-        enumerable: true,
-      });
-    }
-    defineEventHandler(window, "load");
-    defineEventHandler(window, "unload");
+    defineEventHandler(window, "load", null);
+    defineEventHandler(window, "unload", null);
 
     const { args, noColor, pid, ppid, unstableFlag } = runtimeStart();
 
diff --git a/cli/tests/034_onload/main.ts b/cli/tests/034_onload/main.ts
index db6ca669a3..aca38869e1 100644
--- a/cli/tests/034_onload/main.ts
+++ b/cli/tests/034_onload/main.ts
@@ -1,6 +1,9 @@
 import { assert } from "../../../std/testing/asserts.ts";
 import "./imported.ts";
 
+assert(window.hasOwnProperty("onload"));
+assert(window.onload === null);
+
 const eventHandler = (e: Event): void => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in event handler (main)`);
diff --git a/docs/runtime/program_lifecycle.md b/docs/runtime/program_lifecycle.md
index f0ebbd4487..72e21c4f4b 100644
--- a/docs/runtime/program_lifecycle.md
+++ b/docs/runtime/program_lifecycle.md
@@ -75,4 +75,5 @@ defined in `imported.ts`.
 
 In other words, you can register multiple `window.addEventListener` `"load"` or
 `"unload"` events, but only the last loaded `window.onload` or `window.onunload`
-events will be executed.
+event handlers will be executed. It is preferable to use `addEventListener` when
+possible for this reason.