refactor(@angular-devkit/build-angular): refactor the DevServerBuilder to be extendable, so you can override the webpack configuration

Author: mdasberg

packages/angular_devkit/build_angular/src/dev-server/index.ts

@@ -111,9 +111,7 @@ export class DevServerBuilder implements Builder<DevServerBuilderOptions> {
       // Replace the assets in options with the normalized version.
       tap((assetPatternObjects => browserOptions.assets = assetPatternObjects)),
       concatMap(() => new Observable(obs => {
-        const browserBuilder = new BrowserBuilder(this.context);
-        const webpackConfig = browserBuilder.buildWebpackConfig(
-          root, projectRoot, host, browserOptions as NormalizedBrowserBuilderSchema);
+        const webpackConfig = this.buildWebpackConfig(root, projectRoot, host, browserOptions);
         const statsConfig = getWebpackStatsConfig(browserOptions.verbose);
 
         let webpackDevServerConfig: WebpackDevServerConfigurationOptions;
@@ -233,6 +231,19 @@ export class DevServerBuilder implements Builder<DevServerBuilderOptions> {
       })));
   }
 
+  buildWebpackConfig(
+    root: Path,
+    projectRoot: Path,
+    host: virtualFs.Host<fs.Stats>,
+    browserOptions: BrowserBuilderSchema,
+  ) {
+    const browserBuilder = new BrowserBuilder(this.context);
+    const webpackConfig = browserBuilder.buildWebpackConfig(
+      root, projectRoot, host, browserOptions as NormalizedBrowserBuilderSchema);
+
+    return webpackConfig;
+  }
+
   private _buildServerConfig(
     root: Path,
     projectRoot: Path,
@@ -465,5 +476,4 @@ export class DevServerBuilder implements Builder<DevServerBuilderOptions> {
   }
 }
 
-
 export default DevServerBuilder;