fix: use in-process Harness API for local plugin connections

src/channels/shared/harness-mux.mjs

@@ -0,0 +1,123 @@
+// The client owns callback ordering and reconnects. Hooks run immediately;
+// rejected hook promises also close this subscription, without adding a queue.
+function invoke(callback, value, onError) {
+  try {
+    const result = callback?.(value);
+    if (result && typeof result.then === 'function') Promise.resolve(result).catch(onError);
+  } catch (error) {
+    onError(error);
+  }
+}
+
+async function watchInProcessMux({ apiProxy, rpcId, signal, onOpen, onEnvelope }) {
+  const controller = new AbortController();
+  const close = () => controller.abort(signal.reason);
+  let iterator;
+  let pending;
+  let failure;
+  const fail = (error) => {
+    if (controller.signal.aborted) return;
+    failure = error;
+    close();
+  };
+  signal.addEventListener('abort', close, { once: true });
+  try {
+    iterator = apiProxy.events.mux({ rpcId, payload: {} }, controller.signal)[Symbol.asyncIterator]();
+    // mux registers listeners eagerly, but its generator installs abort/finally
+    // cleanup only on the first next(). Start it even if mux itself aborted us.
+    pending = Promise.resolve(iterator.next());
+    if (!controller.signal.aborted) invoke(onOpen, close, fail);
+    while (!controller.signal.aborted) {
+      const { value, done } = await pending;
+      if (done || controller.signal.aborted) break;
+      invoke(onEnvelope, {
+        type: 'server-request',
+        rpcId: value?.rpcId,
+        method: value?.payload?.type,
+        payload: value?.payload,
+      }, fail);
+      if (!controller.signal.aborted) pending = Promise.resolve(iterator.next());
+    }
+  } catch (error) {
+    fail(error);
+  } finally {
+    const cancelled = controller.signal.aborted;
+    signal.removeEventListener('abort', close);
+    // return() alone cannot wake an idle generator's pending next(). Abort
+    // first, then drain that read and return (discarding any queued replay).
+    close();
+    await pending?.catch(() => undefined);
+    try {
+      await iterator?.return?.();
+    } catch (error) {
+      if (!cancelled) failure ??= error;
+    }
+  }
+  if (failure) throw failure;
+}
+
+function watchWebSocketMux({ baseUrl, createWebSocket, signal, onOpen, onEnvelope, onMalformed }) {
+  const url = new URL('/api/events.mux', baseUrl);
+  url.protocol = url.protocol === 'https:' ? 'wss:' : 'ws:';
+  return new Promise((resolve, reject) => {
+    const socket = createWebSocket(url.toString());
+    let opened = false;
+    let finished = false;
+    const finish = (error) => {
+      if (finished) return;
+      finished = true;
+      socket.removeEventListener('open', handleOpen);
+      socket.removeEventListener('message', handleMessage);
+      socket.removeEventListener('close', handleClose);
+      socket.removeEventListener('error', handleError);
+      signal.removeEventListener('abort', handleAbort);
+      try {
+        if (socket.readyState === 0 || socket.readyState === 1) socket.close();
+      } catch {
+        // Some implementations reject closing while still connecting.
+      }
+      if (error && !signal.aborted) reject(error);
+      else resolve();
+    };
+    const close = () => finish();
+    const handleOpen = () => {
+      if (finished || opened) return;
+      opened = true;
+      invoke(onOpen, close, finish);
+    };
+    const handleMessage = (event) => {
+      if (finished) return;
+      let envelope;
+      try {
+        if (typeof event.data !== 'string') throw new Error('binary WebSocket frame');
+        envelope = JSON.parse(event.data);
+      } catch (error) {
+        invoke(onMalformed, error, () => undefined);
+        return;
+      }
+      invoke(onEnvelope, envelope, finish);
+    };
+    const handleClose = () => finish(opened ? undefined : new Error(
+      'Harness event mux WebSocket closed before opening',
+    ));
+    const handleError = () => finish(new Error(opened
+      ? 'Harness event mux WebSocket failed'
+      : 'Harness event mux WebSocket failed before opening'));
+    const handleAbort = () => finish();
+    socket.addEventListener('open', handleOpen);
+    socket.addEventListener('message', handleMessage);
+    socket.addEventListener('close', handleClose, { once: true });
+    socket.addEventListener('error', handleError, { once: true });
+    signal.addEventListener('abort', handleAbort, { once: true });
+    if (signal.aborted) handleAbort();
+  });
+}
+
+/** Watch one mux subscription; an explicit URL retains the HTTP/WS transport. */
+export async function watchHarnessMux(options) {
+  if (options.signal.aborted) return;
+  if (options.baseUrl !== undefined && options.baseUrl !== null) {
+    return watchWebSocketMux(options);
+  }
+  return watchInProcessMux(options);
+}