add pretty message if port already in use(#927) (#932)

* add pretty message if port already use(#927)

* fix console async nature

* fix linter

* clean callbacks code

* Check package.json for the startup script

* fix path to package

* omit callback

* remove extra check, code execute in try block

* + reason for change start listen port of node http

* remove extra code for search package

bin/next-dev

@@ -2,9 +2,10 @@
 import 'source-map-support/register'
 import { resolve, join } from 'path'
 import parseArgs from 'minimist'
-import { existsSync } from 'fs'
+import { existsSync, readFileSync } from 'fs'
 import Server from '../server'
 import { printAndExit } from '../lib/utils'
+import pkgUp from 'pkg-up'
 
 process.env.NODE_ENV = process.env.NODE_ENV || 'development'
 
@@ -61,6 +62,15 @@ srv.start(argv.port)
   }
 })
 .catch((err) => {
-  console.error(err)
-  process.exit(1)
+  if (err.code === 'EADDRINUSE') {
+    let errorMessage = `Port ${argv.port} is already in use.`
+    const pkgAppPath = pkgUp.sync('.')
+    const appPackage = JSON.parse(readFileSync(pkgAppPath, 'utf8'))
+    const nextScript = Object.entries(appPackage.scripts).find(scriptLine => scriptLine[1] === 'next')
+    if (nextScript) errorMessage += `\nUse \`npm run ${nextScript[0]} -- -p <some other port>\`.`
+    console.error(errorMessage)
+  } else {
+    console.error(err)
+  }
+  process.nextTick(() => process.exit(1))
 })

package.json

@@ -70,6 +70,7 @@
     "mkdirp-then": "1.2.0",
     "mz": "2.6.0",
     "path-match": "1.2.4",
+    "pkg-up": "1.0.0",
     "react": "15.4.2",
     "react-dom": "15.4.2",
     "react-hot-loader": "3.0.0-beta.6",

server/index.js

@@ -119,10 +119,10 @@ export default class Server {
     await this.prepare()
     this.http = http.createServer(this.getRequestHandler())
     await new Promise((resolve, reject) => {
-      this.http.listen(port, (err) => {
-        if (err) return reject(err)
-        resolve()
-      })
+      // This code catches EADDRINUSE error if the port is already in use
+      this.http.on('error', reject)
+      this.http.on('listening', () => resolve())
+      this.http.listen(port)
     })
   }