Worker: report close code 0 when the parent terminates a Web Worker

src/jsc/web_worker.rs

@@ -863,8 +863,10 @@ impl WebWorker {
         let promise = match vm.as_mut().load_entry_point_for_web_worker(path) {
             Ok(p) => p,
             Err(_) => {
-                // process.exit() may have run during load; don't clobber its code.
-                if !self.exit_called.load(Ordering::Relaxed) {
+                // Neither a process.exit() during load nor the parent's terminate() is a load failure.
+                if !self.exit_called.load(Ordering::Relaxed)
+                    && !self.termination_requested_by_parent()
+                {
                     vm.as_mut().exit_handler.exit_code = 1;
                 }
                 self.flush_logs(vm);
@@ -1093,6 +1095,14 @@ impl WebWorker {
             && !self.exit_called.load(Ordering::Relaxed)
     }
 
+    /// The parent's `terminate()` asked this thread to stop. Worker thread. Taken under the
+    /// `vm_handle` lock that `request_termination` holds while it sets both flags, so a thread
+    /// that already saw `requested_terminate` never reads a stale `false` here.
+    fn termination_requested_by_parent(&self) -> bool {
+        let _handle = self.vm_handle.lock();
+        self.terminated_by_parent.load(Ordering::Relaxed)
+    }
+
     /// process.exit() inside the worker. Worker-thread only.
     ///
     /// Takes `&self` (not `&mut self`) because `request_termination` /

test/js/web/workers/worker.test.ts

@@ -510,6 +510,24 @@ describe("web worker", () => {
       w.terminate();
     });
 
+    // The 'close' code is what the worker passed to process.exit(), or 0. A worker stopped by its
+    // parent did not choose one, whether terminate() lands while the entry module is still
+    // evaluating or once its loop is idle.
+    test.each([
+      // The first message is posted from the entry's top-level code, which then never yields.
+      ["busy evaluating its entry module", "postMessage('up'); for (;;) {}"],
+      // A reply to a parent message comes from the worker's event loop, after the entry has loaded.
+      ["idle in its event loop", "self.onmessage = () => postMessage('up'); setInterval(() => {}, 1000)"],
+    ])("close code is 0 after terminate() of a worker that is %s", async (_, body) => {
+      const w = new Worker("data:text/javascript," + encodeURIComponent(body));
+      w.postMessage("ping");
+      await once(w, "message");
+      const closed = once(w, "close");
+      w.terminate();
+      const [event] = await closed;
+      expect({ code: event.code, wasClean: event.wasClean }).toEqual({ code: 0, wasClean: true });
+    });
+
     // As in browsers and Node: not an error, the message is dropped.
     test("postMessage() to a terminated worker is a no-op", async () => {
       const w = new Worker("data:text/javascript,postMessage('up')");
@@ -679,6 +697,8 @@ describe("web worker", () => {
     // after the request must release, not build script values under it.
     test("terminate() while fs.readFile completions keep arriving", async () => {
       using dir = tempDir("worker-readfile-churn", { "f.bin": Buffer.alloc(65536, 7) });
+      // Each round boots 4 workers; a debug build spends ~0.5s per round, so it runs fewer.
+      const rounds = isDebug ? 4 : 12;
       await using proc = Bun.spawn({
         cmd: [
           bunExe(),
@@ -687,7 +707,7 @@ describe("web worker", () => {
              let n = 0; (function pump(){ while (n < 16) { n++; readFile(\${JSON.stringify(process.argv[1])}, () => { n--; setImmediate(pump) }) } })();
              postMessage("busy")\`;
            const url = URL.createObjectURL(new Blob([src]));
-           for (let r = 0; r < 12; r++) await Promise.all(Array.from({ length: 4 }, (_, i) => new Promise(res => {
+           for (let r = 0; r < ${rounds}; r++) await Promise.all(Array.from({ length: 4 }, (_, i) => new Promise(res => {
              const w = new Worker(url); w.addEventListener("close", res); w.onmessage = () => setTimeout(() => w.terminate(), (r + i) % 10) })));
            console.log("PASS");`,
           path.join(String(dir), "f.bin"),