chore: Return better error on WDA startup timeout (#801)

lib/xcodebuild.js

@@ -405,12 +405,13 @@ class XcodeBuild {
     this.log.debug(`Waiting up to ${this.launchTimeout}ms for WebDriverAgent to start`);
     let currentStatus = null;
     try {
-      let retries = parseInt(`${this.launchTimeout / 500}`, 10);
+      const retries = Math.trunc(this.launchTimeout / 500);
       await retryInterval(retries, 1000, async () => {
         if (this._didProcessExit) {
           // there has been an error elsewhere and we need to short-circuit
-          return;
+          return currentStatus;
         }
+
         const proxyTimeout = this.noSessionProxy.timeout;
         this.noSessionProxy.timeout = 1000;
         try {
@@ -434,10 +435,11 @@ class XcodeBuild {
 
       this.log.debug(`WebDriverAgent successfully started after ${timer.getDuration().asMilliSeconds.toFixed(0)}ms`);
     } catch (err) {
-      // at this point, if we have not had any errors from xcode itself (reported
-      // elsewhere), we can let this go through and try to create the session
-      this.log.debug(err.message);
-      this.log.warn(`Getting status of WebDriverAgent on device timed out. Continuing`);
+      this.log.debug(err.stack);
+      throw new Error(
+        `We were not able to retrieve the /status response from the WebDriverAgent server after ${this.launchTimeout}ms timeout.` +
+        `Try to increase the value of 'appium:wdaLaunchTimeout' capability as a possible workaround.`
+      );
     }
     return currentStatus;
   }