fix(server): fix setupExitSignals usage (#2181)

* fix(server): pass server data to exit signal setup as object
* test(server): add exit signal tests
* style(test): fix lint problem

Author: knagaitsev

bin/webpack-dev-server.js

@@ -19,8 +19,14 @@ const getVersions = require('../lib/utils/getVersions');
 constoptions=require('./options');
 
 letserver;
-
-setupExitSignals(server);
+constserverData={
+server: null,
+};
+// we must pass an object that contains the server object as a property so that
+// we can update this server property later, and setupExitSignals will be able to
+// recognize that the server has been instantiated, because we will set
+// serverData.server to the new server object.
+setupExitSignals(serverData);
 
 // Prefer the local installation of webpack-dev-server
 if(importLocal(__filename)){
@@ -98,6 +104,7 @@ function startDevServer(config, options) {
 
 try{
 server=newServer(compiler,options,log);
+serverData.server=server;
 }catch(err){
 if(err.name==='ValidationError'){
 log.error(colors.error(options.stats.colors,err.message));

lib/utils/setupExitSignals.js

@@ -2,11 +2,11 @@
 
 constsignals=['SIGINT','SIGTERM'];
 
-functionsetupExitSignals(server){
+functionsetupExitSignals(serverData){
 signals.forEach((signal)=>{
 process.on(signal,()=>{
-if(server){
-server.close(()=>{
+if(serverData.server){
+serverData.server.close(()=>{
 // eslint-disable-next-line no-process-exit
 process.exit();
 });

test/server/utils/setupExitSignals.test.js

@@ -0,0 +1,57 @@
+'use strict';
+
+constsetupExitSignals=require('../../../lib/utils/setupExitSignals');
+
+describe('setupExitSignals',()=>{
+letserver;
+letexitSpy;
+constsignals=['SIGINT','SIGTERM'];
+
+beforeAll(()=>{
+exitSpy=jest.spyOn(process,'exit').mockImplementation(()=>{});
+server={
+close: jest.fn((callback)=>{
+callback();
+}),
+};
+});
+
+afterEach(()=>{
+exitSpy.mockReset();
+server.close.mockClear();
+signals.forEach((signal)=>{
+process.removeAllListeners(signal);
+});
+});
+
+signals.forEach((signal)=>{
+it(`should exit process (${signal}, server never defined)`,(done)=>{
+setupExitSignals({
+server: null,
+});
+process.emit(signal);
+setTimeout(()=>{
+expect(exitSpy.mock.calls.length).toEqual(1);
+done();
+},1000);
+});
+
+it(`should close server, then exit process (${signal}, server defined before signal)`,(done)=>{
+constserverData={
+server: null,
+};
+setupExitSignals(serverData);
+
+setTimeout(()=>{
+serverData.server=server;
+process.emit(signal);
+},500);
+
+setTimeout(()=>{
+expect(server.close.mock.calls.length).toEqual(1);
+expect(exitSpy.mock.calls.length).toEqual(1);
+done();
+},1500);
+});
+});
+});