From d720d3db738d2cefe1a5537629f94c9689300f9b Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Tue, 16 Feb 2021 10:38:57 -0500
Subject: [PATCH] refactor(@angular-devkit/build-optimizer): improve
 transitional Webpack 5 compatibility

This change provides both Webpack 4 and 5 compatible types for the the build optimizer Webpack plugin.
---
 .../build_optimizer/src/_golden-api.d.ts           |  2 +-
 .../angular_devkit/build_optimizer/package.json    |  4 ++++
 .../src/build-optimizer/webpack-plugin.ts          |  6 +++---
 .../build_optimizer/src/webpack.d.ts               | 14 ++++++++++++++
 4 files changed, 22 insertions(+), 4 deletions(-)
 create mode 100644 packages/angular_devkit/build_optimizer/src/webpack.d.ts

diff --git a/etc/api/angular_devkit/build_optimizer/src/_golden-api.d.ts b/etc/api/angular_devkit/build_optimizer/src/_golden-api.d.ts
index 5482d25058..d366778a02 100644
--- a/etc/api/angular_devkit/build_optimizer/src/_golden-api.d.ts
+++ b/etc/api/angular_devkit/build_optimizer/src/_golden-api.d.ts
@@ -3,7 +3,7 @@ export declare function buildOptimizer(options: BuildOptimizerOptions): Transfor
 export declare const buildOptimizerLoaderPath: string;
 
 export declare class BuildOptimizerWebpackPlugin {
-    apply(compiler: Compiler): void;
+    apply(compiler: Compiler | WebpackFourCompiler): void;
 }
 
 export default function buildOptimizerLoader(this: {
diff --git a/packages/angular_devkit/build_optimizer/package.json b/packages/angular_devkit/build_optimizer/package.json
index a3c57413da..19031a1ddf 100644
--- a/packages/angular_devkit/build_optimizer/package.json
+++ b/packages/angular_devkit/build_optimizer/package.json
@@ -22,5 +22,9 @@
     "webpack": {
       "optional": true
     }
+  },
+  "devDependencies": {
+    "@types/webpack": "^4.41.22",
+    "webpack": "5.21.2"
   }
 }
diff --git a/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-plugin.ts b/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-plugin.ts
index 94d8a9f009..55a67c6e77 100644
--- a/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-plugin.ts
+++ b/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-plugin.ts
@@ -5,15 +5,15 @@
  * 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 { Compiler } from 'webpack';
+import { Compiler, WebpackFourCompiler } from 'webpack';
 
 interface ModuleData {
   resourceResolveData: { descriptionFileData?: { typings?: string } };
 }
 
 export class BuildOptimizerWebpackPlugin {
-  apply(compiler: Compiler) {
-    compiler.hooks.normalModuleFactory.tap('BuildOptimizerWebpackPlugin', nmf => {
+  apply(compiler: Compiler | WebpackFourCompiler) {
+    (compiler as Compiler).hooks.normalModuleFactory.tap('BuildOptimizerWebpackPlugin', nmf => {
       // tslint:disable-next-line: no-any
       nmf.hooks.module.tap('BuildOptimizerWebpackPlugin', (module, data) => {
         const { descriptionFileData } = (data as ModuleData).resourceResolveData;
diff --git a/packages/angular_devkit/build_optimizer/src/webpack.d.ts b/packages/angular_devkit/build_optimizer/src/webpack.d.ts
new file mode 100644
index 0000000000..c9ac20d20d
--- /dev/null
+++ b/packages/angular_devkit/build_optimizer/src/webpack.d.ts
@@ -0,0 +1,14 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * 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 * as webpack from 'webpack';
+import { Compiler as webpack4Compiler } from '@types/webpack';
+
+// Webpack 5 transition support types
+declare module 'webpack' {
+  export type WebpackFourCompiler = webpack4Compiler;
+}