From 996a87b168ea22592313803d1d068065e438787f Mon Sep 17 00:00:00 2001
From: Benjamin Gruenbaum <benjamingr@gmail.com>
Date: Mon, 9 Nov 2020 18:49:19 +0200
Subject: [PATCH] fix(op_crates/web): handler order when reassign (#8264)

---
 op_crates/web/02_abort_signal.js       | 27 +++++++++++++++++++-------
 op_crates/web/abort_controller_test.js | 18 +++++++++++++++++
 2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/op_crates/web/02_abort_signal.js b/op_crates/web/02_abort_signal.js
index 53745c52ba..5e8943161e 100644
--- a/op_crates/web/02_abort_signal.js
+++ b/op_crates/web/02_abort_signal.js
@@ -64,22 +64,35 @@
   }
 
   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;
+  }
   function defineEventHandler(emitter, name) {
     // HTML specification section 8.1.5.1
     Object.defineProperty(emitter, `on${name}`, {
       get() {
-        return this[handlerSymbol]?.get(name);
+        return this[handlerSymbol]?.get(name)?.handler;
       },
       set(value) {
-        const oldListener = this[handlerSymbol]?.get(name);
-        if (oldListener) {
-          this.removeEventListener(name, oldListener);
-        }
         if (!this[handlerSymbol]) {
           this[handlerSymbol] = new Map();
         }
-        this.addEventListener(name, value);
-        this[handlerSymbol].set(value);
+        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,
diff --git a/op_crates/web/abort_controller_test.js b/op_crates/web/abort_controller_test.js
index 4d37419860..a65bc69ff8 100644
--- a/op_crates/web/abort_controller_test.js
+++ b/op_crates/web/abort_controller_test.js
@@ -95,6 +95,23 @@ function abortSignalEventOrder() {
   assertEquals(arr[1], 2);
   assertEquals(arr[2], 3);
 }
+
+function abortSignalEventOrderComplex() {
+  const arr = [];
+  const controller = new AbortController();
+  const { signal } = controller;
+  signal.addEventListener("abort", () => arr.push(1));
+  signal.onabort = () => {
+    throw new Error();
+  };
+  signal.addEventListener("abort", () => arr.push(3));
+  signal.onabort = () => arr.push(2);
+  controller.abort();
+  assertEquals(arr[0], 1);
+  assertEquals(arr[1], 2);
+  assertEquals(arr[2], 3);
+}
+
 function abortSignalHandlerLocation() {
   const controller = new AbortController();
   const { signal } = controller;
@@ -109,6 +126,7 @@ function main() {
   controllerHasProperToString();
   abortSignalIllegalConstructor();
   abortSignalEventOrder();
+  abortSignalEventOrderComplex();
   abortSignalHandlerLocation();
 }