fix: improved webpack version check (#638)

Author: cap-Bernardito

src/index.js

@@ -1,6 +1,6 @@
 /* eslint-disable class-methods-use-this */
 
-import webpack, { version as webpackVersion } from 'webpack';
+import webpack from 'webpack';
 
 import { validate } from 'schema-utils';
 
@@ -103,7 +103,9 @@ class MiniCssExtractPlugin {
 
   /** @param {import("webpack").Compiler} compiler */
   apply(compiler) {
-    const isWebpack4 = compiler.webpack ? false : webpackVersion[0] === '4';
+    const isWebpack4 = compiler.webpack
+      ? false
+      : typeof compiler.resolvers !== 'undefined';
 
     if (!isWebpack4) {
       const { splitChunks } = compiler.options.optimization;

src/loader.js

@@ -1,7 +1,6 @@
 import path from 'path';
 
 import loaderUtils from 'loader-utils';
-import { version as webpackVersion } from 'webpack';
 import NodeTemplatePlugin from 'webpack/lib/node/NodeTemplatePlugin';
 import NodeTargetPlugin from 'webpack/lib/node/NodeTargetPlugin';
 import LibraryTemplatePlugin from 'webpack/lib/LibraryTemplatePlugin';
@@ -103,7 +102,9 @@ export function pitch(request) {
 
   let source;
 
-  const isWebpack4 = childCompiler.webpack ? false : webpackVersion[0] === '4';
+  const isWebpack4 = childCompiler.webpack
+    ? false
+    : typeof childCompiler.resolvers !== 'undefined';
 
   if (isWebpack4) {
     childCompiler.hooks.afterCompile.tap(pluginName, (compilation) => {