From 44d48efe53dcf2939c0b1b83d54dd52e9811ff32 Mon Sep 17 00:00:00 2001
From: lojhan <viniciuslojhan@gmail.com>
Date: Sun, 5 Apr 2026 17:51:09 -0300
Subject: [PATCH] fix: preserve native Event/dispatchEvent in jsdom setup for
 Deno compatibility
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Under isolation:process, Deno spawns a per-test subprocess and fires
dispatchLoadEvent() on exit using its own native Event constructor.
setupJsdomEnvironment() was unconditionally overwriting globalThis.Event
with jsdom's implementation, causing setTarget() to receive undefined:

  TypeError: Cannot set properties of undefined (setting 'target')
    at setTarget (ext:deno_web/02_event.js:97:29)

Apply the same save/restore pattern already present in
setupHappyDomEnvironment(): capture the runtime's native Event,
CustomEvent, and dispatchEvent before constructing JSDOM, then
restore them after. isolation:none is unaffected as no subprocess
teardown occurs. Fixes all 24 matrix combinations (24/24 ✅).
---
 src/dom-env.ts | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/dom-env.ts b/src/dom-env.ts
index 34859c5..81f2e9d 100644
--- a/src/dom-env.ts
+++ b/src/dom-env.ts
@@ -82,6 +82,15 @@ export const setupJsdomEnvironment = async (
       );
     }
 
+    // Save native event primitives before jsdom replaces them.
+    // Deno's runtime teardown fires dispatchLoadEvent() on process exit using
+    // its own native Event constructor — if jsdom's Event is installed instead,
+    // setTarget() receives undefined and throws "Cannot set properties of
+    // undefined (setting 'target')".
+    const existingDispatchEvent = globalThis.dispatchEvent;
+    const existingEvent = globalThis.Event;
+    const existingCustomEvent = globalThis.CustomEvent;
+
     const { JSDOM } = mod;
     const dom = new JSDOM('', {
       url: options.runtimeOptions.domUrl,
@@ -96,11 +105,20 @@ export const setupJsdomEnvironment = async (
     defineGlobal('Node', dom.window.Node);
     defineGlobal('Text', dom.window.Text);
     defineGlobal('SVGElement', dom.window.SVGElement);
-    defineGlobal('Event', dom.window.Event);
-    defineGlobal('CustomEvent', dom.window.CustomEvent);
     defineGlobal('MutationObserver', dom.window.MutationObserver);
     defineGlobal('requestAnimationFrame', dom.window.requestAnimationFrame);
     defineGlobal('cancelAnimationFrame', dom.window.cancelAnimationFrame);
+
+    // Prefer the runtime's native Event constructors so that Deno's internal
+    // event dispatch (e.g. load/beforeunload) continues to work correctly.
+    defineGlobal('Event', typeof existingEvent === 'function' ? existingEvent : dom.window.Event);
+    defineGlobal('CustomEvent', typeof existingCustomEvent === 'function' ? existingCustomEvent : dom.window.CustomEvent);
+
+    if (typeof existingDispatchEvent === 'function') {
+      globalThis.dispatchEvent = existingDispatchEvent;
+    } else {
+      globalThis.dispatchEvent = dom.window.dispatchEvent.bind(dom.window) as unknown as typeof globalThis.dispatchEvent;
+    }
   }
 
   applyReactActEnvironment(Boolean(options.enableReactActEnvironment));