fix: Worker hangs when posting "undefined" as message (#8920)

This commit fixes hang in web workers occuring when sending
"undefined" as message value. It is a temporary band-aid
until proper structured close is implemented.

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/cli/tests/workers_test.ts b/cli/tests/workers_test.ts
index 9cbc864bd..70ecbb828 100644
--- a/cli/tests/workers_test.ts
+++ b/cli/tests/workers_test.ts
@@ -385,6 +385,31 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "Worker post undefined",
+  fn: async function (): Promise<void> {
+    const promise = deferred();
+    const worker = new Worker(
+      new URL("./worker_post_undefined.ts", import.meta.url).href,
+      { type: "module" },
+    );
+
+    const handleWorkerMessage = (e: MessageEvent): void => {
+      console.log("main <- worker:", e.data);
+      worker.terminate();
+      promise.resolve();
+    };
+
+    worker.addEventListener("messageerror", () => console.log("message error"));
+    worker.addEventListener("error", () => console.log("error"));
+    worker.addEventListener("message", handleWorkerMessage);
+
+    console.log("\npost from parent");
+    worker.postMessage(undefined);
+    await promise;
+  },
+});
+
 Deno.test("Worker inherits permissions", async function () {
   const promise = deferred();
   const worker = new Worker(