faster iOS device connection

Summary:
First connection attempt to iOS device was only made after 3000ms. This caused all iOS devices only show up after this delay.
Now, the devices are queried immediately.

Reviewed By: passy

Differential Revision: D9613057

fbshipit-source-id: a14e3f02576ec5e159f4002bf68efe53236dcc50

src/dispatcher/iOSDevice.js

@@ -9,7 +9,10 @@ import type {ChildProcess} from 'child_process';
 import type {Store} from '../reducers/index.js';
 import type Logger from '../fb-stubs/Logger.js';
 
+import {promisify} from 'util';
 import child_process from 'child_process';
+const exec = promisify(child_process.exec);
+const execFile = promisify(child_process.execFile);
 import IOSDevice from '../devices/IOSDevice';
 
 type iOSSimulatorDevice = {|
@@ -22,43 +25,20 @@ type iOSSimulatorDevice = {|
 type IOSDeviceMap = {[id: string]: Array<iOSSimulatorDevice>};
 
 // start port forwarding server for real device connections
-const portForwarder: ChildProcess = child_process.exec(
+const portForwarder: ChildProcess = exec(
   'PortForwardingMacApp.app/Contents/MacOS/PortForwardingMacApp -portForward=8088 -multiplexChannelPort=8078',
 );
 window.addEventListener('beforeunload', () => {
   portForwarder.kill();
 });
 
-function querySimulatorDevices(): Promise<IOSDeviceMap> {
+function querySimulatorDevices(store: Store): Promise<IOSDeviceMap> {
-  return new Promise((resolve, reject) => {
-    child_process.execFile(
-      'xcrun',
-      ['simctl', 'list', 'devices', '--json'],
-      {encoding: 'utf8'},
-      (err, stdout) => {
-        if (err) {
-          reject(err);
-        }
-
-        try {
-          const {devices} = JSON.parse(stdout.toString());
-          resolve(devices);
-        } catch (err) {
-          reject(err);
-        }
-      },
-    );
-  });
-}
-
-export default (store: Store, logger: Logger) => {
-  // monitoring iOS devices only available on MacOS.
-  if (process.platform !== 'darwin') {
-    return;
-  }
-  const simulatorUpdateInterval = setInterval(() => {
   const {connections} = store.getState();
-    querySimulatorDevices()
+
+  return execFile('xcrun', ['simctl', 'list', 'devices', '--json'], {
+    encoding: 'utf8',
+  })
+    .then(({stdout}) => JSON.parse(stdout).devices)
     .then((simulatorDevices: IOSDeviceMap) => {
       const simulators: Array<iOSSimulatorDevice> = Object.values(
         simulatorDevices,
@@ -81,11 +61,7 @@ export default (store: Store, logger: Logger) => {
           // create device
           store.dispatch({
             type: 'REGISTER_DEVICE',
-              payload: new IOSDevice(
+            payload: new IOSDevice(simulator.udid, 'emulator', simulator.name),
-                simulator.udid,
-                'emulator',
-                simulator.name,
-              ),
           });
         } else if (!isRunning && currentDeviceIDs.has(simulator.udid)) {
           deviceIDsToRemove.add(simulator.udid);
@@ -99,10 +75,22 @@ export default (store: Store, logger: Logger) => {
           payload: deviceIDsToRemove,
         });
       }
-      })
+    });
-      .catch(err => {
+}
+
+export default (store: Store, logger: Logger) => {
+  // monitoring iOS devices only available on MacOS.
+  if (process.platform !== 'darwin') {
+    return;
+  }
+  querySimulatorDevices(store)
+    .then(() => {
+      const simulatorUpdateInterval = setInterval(() => {
+        querySimulatorDevices(store).catch(err => {
           console.error(err);
           clearInterval(simulatorUpdateInterval);
         });
       }, 3000);
+    })
+    .catch(console.error);
 };