feat: skip successful Metro server requests if --verbose not set (#291)

Summary:
---------
Metro server can become too verbose if there are a lot of assets due to morgan verbosely logging every request. Trying to make use of `verbose` flag to allow users skipping successful requests if 'verbose' is set to false (default)

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Test Plan:
----------
1. run `react-native start`
Expected Result: no console output on a successful request
2. run `react-native start --verbose`
Expected Result: console output for every request

<!-- Write your test plan here (**REQUIRED**). If you changed any code, please provide us with clear instructions on how you verified your changes work. Bonus points for screenshots and videos! Increase test coverage whenever possible. -->

Author: vancehu

packages/cli/src/commands/server/runServer.js

@@ -8,16 +8,14 @@
  */
 
 import Metro from 'metro';
-
 import {Terminal} from 'metro-core';
-
 import morgan from 'morgan';
 import path from 'path';
+import logger from '../../tools/logger';
 import type {ContextT} from '../../tools/types.flow';
 import messageSocket from './messageSocket';
 import webSocketProxy from './webSocketProxy';
 import MiddlewareManager from './middleware/MiddlewareManager';
-
 import loadMetroConfig from '../../tools/loadMetroConfig';
 
 export type Args = {|
@@ -62,7 +60,14 @@ async function runServer(argv: Array<string>, ctx: ContextT, args: Args) {
     watchFolders: metroConfig.watchFolders,
   });
 
-  middlewareManager.getConnectInstance().use(morgan('combined'));
+  middlewareManager.getConnectInstance().use(
+    morgan(
+      'combined',
+      !logger.isVerbose() && {
+        skip: (req, res) => res.statusCode < 400,
+      },
+    ),
+  );
 
   metroConfig.watchFolders.forEach(
     middlewareManager.serveStatic.bind(middlewareManager),

packages/cli/src/tools/logger.js

@@ -40,6 +40,8 @@ const setVerbose = (level: boolean) => {
   verbose = level;
 };
 
+const isVerbose = () => verbose;
+
 export default {
   success,
   info,
@@ -48,4 +50,5 @@ export default {
   debug,
   log,
   setVerbose,
+  isVerbose,
 };