Make sure flipper server initialization errors are propagated properly

Summary:
This diff makes sure that errors are propagated similarly in flipper desktop and browser version, and that they are shown in either case.

Since in the browser version, the UI loads after the error happened, we'll store the error so that any client connecting in the future will read and report it.

Also added a `--failFast` flag to flipper-server, so that the process exits immediately if misconfigured, which is convenient in CI use cases and such

Reviewed By: nikoant

Differential Revision: D33348922

fbshipit-source-id: 0f584104f881141fde38da3f0031748415343ea2

desktop/flipper-server/src/index.tsx

@@ -7,6 +7,7 @@
  * @format
  */
 
+import process from 'process';
 import chalk from 'chalk';
 import path from 'path';
 import {startFlipperServer} from './startFlipperServer';
@@ -37,6 +38,12 @@ const argv = yargs
       type: 'boolean',
       default: true,
     },
+    failFast: {
+      describe:
+        'Exit the process immediately if the server cannot start, for example due to an incorrect configuration.',
+      type: 'boolean',
+      default: false,
+    },
   })
   .version('DEV')
   .help()
@@ -64,12 +71,19 @@ async function start() {
     staticDir,
     entry: 'index.web.dev.html',
   });
+  const flipperServer = await startFlipperServer(rootDir, staticDir);
+  if (argv.failFast) {
+    flipperServer.on('server-state', ({state}) => {
+      if (state === 'error') {
+        process.exit(1);
+      }
+    });
+  }
+  await flipperServer.connect();
 
-  const [flipperServer] = await Promise.all([
-    startFlipperServer(rootDir, staticDir),
-    argv.bundler ? startWebServerDev(app, server, socket, rootDir) : undefined,
-  ]);
-
+  if (argv.bundler) {
+    await startWebServerDev(app, server, socket, rootDir);
+  }
   startSocketServer(flipperServer, socket);
 }
 
@@ -85,6 +99,6 @@ start()
     }
   })
   .catch((e) => {
-    console.error(chalk.red('Server error: '), e);
+    console.error(chalk.red('Server startup error: '), e);
     process.exit(1);
   });