fix(@angular-devkit/build-angular): dispose Sass worker resources on Webpack shutdown

Sass Worker instances and resource requests are now cleaned up when the Webpack compiler is shutdown. This removes the need to unreference the workers upon creation.

Fixes #20985

Author: clydin

packages/angular_devkit/build_angular/src/sass/sass-service.ts

@@ -118,13 +118,12 @@ export class SassWorkerImplementation {
   /**
    * Shutdown the Sass render worker.
    * Executing this method will stop any pending render requests.
-   *
-   * The worker is unreferenced upon creation and will not block application exit. This method
-   * is only needed if early cleanup is needed.
    */
   close(): void {
     for (const worker of this.workers) {
-      void worker.terminate();
+      try {
+        void worker.terminate();
+      } catch {}
     }
     this.requests.clear();
   }
@@ -207,7 +206,6 @@ export class SassWorkerImplementation {
       },
     );
 
-    worker.unref();
     mainImporterPort.unref();
 
     return worker;

packages/angular_devkit/build_angular/src/webpack/configs/styles.ts

@@ -108,7 +108,7 @@ export function getStylesConfig(wco: WebpackConfigOptions): webpack.Configuratio
     );
   }
 
-  let sassImplementation: {} | undefined;
+  let sassImplementation: SassWorkerImplementation | undefined;
   try {
     sassImplementation = require('node-sass');
     wco.logger.warn(
@@ -117,6 +117,13 @@ export function getStylesConfig(wco: WebpackConfigOptions): webpack.Configuratio
     );
   } catch {
     sassImplementation = new SassWorkerImplementation();
+    extraPlugins.push({
+      apply(compiler) {
+        compiler.hooks.shutdown.tap('sass-worker', () => {
+          sassImplementation?.close();
+        });
+      }
+    });
   }
 
   const assetNameTemplate = assetNameTemplateFactory(hashFormat);