refactor: do not use webpack directly (#3414)

Author: alexander-akait

lib/Server.js

@@ -86,7 +86,7 @@ class Server {
   }
 
   setupProgressPlugin() {
-    const { ProgressPlugin } = require('webpack');
+    const { ProgressPlugin } = this.compiler.webpack || require('webpack');
 
     new ProgressPlugin((percent, msg, addInfo, pluginName) => {
       percent = Math.floor(percent * 100);

lib/utils/DevServerPlugin.js

@@ -1,12 +1,8 @@
 'use strict';
 
-const webpack = require('webpack');
 const ipaddr = require('ipaddr.js');
 const getSocketClientPath = require('./getSocketClientPath');
 
-// @ts-ignore
-const EntryPlugin = webpack.EntryPlugin;
-
 class DevServerPlugin {
   /**
    * @param {?Object} options - Dev-Server options
@@ -252,10 +248,12 @@ class DevServerPlugin {
       additionalEntries.push(hotEntry);
     }
 
+    const webpack = compiler.webpack || require('webpack');
+
     // use a hook to add entries if available
-    if (EntryPlugin) {
+    if (typeof webpack.EntryPlugin !== 'undefined') {
       for (const additionalEntry of additionalEntries) {
-        new EntryPlugin(compiler.context, additionalEntry, {
+        new webpack.EntryPlugin(compiler.context, additionalEntry, {
           // eslint-disable-next-line no-undefined
           name: undefined,
         }).apply(compiler);