From 63a5559f0d8aa772361db350fb41d74d21ba679a Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Thu, 22 Oct 2020 11:29:14 -0400
Subject: [PATCH] fix(@angular-devkit/build-webpack): fully close Webpack 5
 compiler

The Webpack 5 compiler now contains a close function that should be called when the compiler is finished.

(cherry picked from commit dc3cdae7b9038c7bd2e477aeda04d9a96368ef4f)
---
 .../build_webpack/src/webpack/index.ts          | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/packages/angular_devkit/build_webpack/src/webpack/index.ts b/packages/angular_devkit/build_webpack/src/webpack/index.ts
index 6fc1f3751e4a..f4624e0a8605 100644
--- a/packages/angular_devkit/build_webpack/src/webpack/index.ts
+++ b/packages/angular_devkit/build_webpack/src/webpack/index.ts
@@ -52,6 +52,12 @@ export function runWebpack(
 
   return createWebpack({ ...config, watch: false }).pipe(
     switchMap(webpackCompiler => new Observable<BuildResult>(obs => {
+      // Webpack 5 has a compiler level close function
+      // The close function will crash if caching is disabled
+      const compilerClose = webpackCompiler.options.cache !== false
+        ? (webpackCompiler as { close?(callback: () => void): void }).close
+        : undefined;
+
       const callback = (err?: Error, stats?: webpack.Stats) => {
         if (err) {
           return obs.error(err);
@@ -71,7 +77,11 @@ export function runWebpack(
         } as unknown as BuildResult);
 
         if (!config.watch) {
-          obs.complete();
+          if (compilerClose) {
+            compilerClose(() => obs.complete());
+          } else {
+            obs.complete();
+          }
         }
       };
 
@@ -81,7 +91,10 @@ export function runWebpack(
           const watching = webpackCompiler.watch(watchOptions, callback);
 
           // Teardown logic. Close the watcher when unsubscribed from.
-          return () => watching.close(() => { });
+          return () => {
+            watching.close(() => { });
+            compilerClose?.(() => { });
+          };
         } else {
           webpackCompiler.run(callback);
         }