refactor(@angular-devkit/build-angular): improve check port

Author: tiaguinho

packages/angular_devkit/build_angular/src/angular-cli-files/utilities/check-port.ts

@@ -5,39 +5,34 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-
-import { Observable } from 'rxjs';
 const net = require('net');
 
-function getPort(options: any, callback: any, basePort = 49152) {
-  const port = options.port || basePort;
-  const server = net.createServer();
-  server.once('error', 
-    (err: any) => options.port === 0 
-    ? getPort(options, callback, basePort+1)
-    : callback(err, null)
-  );
-  server.once('listening', () => {
-    server.close();
-    callback(null, port);
-  });
-  server.listen(port, options.host);
-}
-
-export function checkPort(port: number, host: string): Observable<number> {
-  return new Observable(obs => {
-    // tslint:disable:no-any
-    getPort({ port, host }, (err: any, foundPort: number) => {
-      if (err) {
-        obs.error(err);
-      } else if (port !== foundPort && port !== 0) {
-        // If the port isn't available and we weren't looking for any port, throw error.
-        obs.error(`Port ${port} is already in use. Use '--port' to specify a different port.`);
-      } else {
-        // Otherwise, our found port is good.
-        obs.next(foundPort);
-        obs.complete();
+export function checkPort(port: number, host: string, basePort = 49152): Promise<number> {
+  return new Promise<number>((resolve, reject) => {
+    function _getPort(portNumber: number) {
+      if (portNumber > 65535) {
+        reject(new Error(`There is no port available.`));
       }
-    });
+
+      const server = net.createServer();
+
+      server.once('error', err => {
+        if (port !== 0 && err.code === 'EADDRINUSE') {
+          // If the port isn't available and we weren't looking for any port, throw error.
+          reject(`Port ${port} is already in use. Use '--port' to specify a different port.`);
+        } else if (port === 0) {
+          reject(err);
+        }
+
+        _getPort(portNumber + 1);
+      })
+      .once('listening', () => {
+        server.close();
+        resolve(portNumber);
+      })
+      .listen(portNumber, host);
+    }
+
+    _getPort(port || basePort);
   });
 }