refactor(@angular-devkit/build-angular): decouple karma builder from webpack plugin callbacks

Decouples the Karma builder from the Webpack plugin by removing the custom
`successCb` and `failureCb` callback mechanism. The builder now idiomaticallly
listens to the standard Karma `run_complete` event on the server instance
to emit builder results.

Author: clydin

packages/angular_devkit/build_angular/src/builders/karma/browser_builder.ts

@@ -8,7 +8,7 @@
 
 import { purgeStaleBuildCache } from '@angular/build/private';
 import type { BuilderContext, BuilderOutput } from '@angular-devkit/architect';
-import type { Config, ConfigOptions, Server } from 'karma';
+import type { ConfigOptions, Server } from 'karma';
 import * as path from 'node:path';
 import type { Configuration } from 'webpack';
 import { getCommonConfig, getStylesConfig } from '../../tools/webpack/configs';
@@ -83,11 +83,11 @@ export function execute(
         logger: context.logger,
       };
 
-      const parsedKarmaConfig = (await karma.config.parseConfig(
+      const parsedKarmaConfig = await karma.config.parseConfig(
         options.karmaConfig && path.resolve(context.workspaceRoot, options.karmaConfig),
         transforms.karmaOptions ? transforms.karmaOptions(karmaOptions) : karmaOptions,
         { promiseConfig: true, throwErrors: true },
-      )) as KarmaConfigOptions;
+      );
 
       if (isCancelled) {
         return;
@@ -109,21 +109,16 @@ export function execute(
         }
       };
 
-      // Pass onto Karma to emit BuildEvents.
-      parsedKarmaConfig.buildWebpack ??= {};
-      if (typeof parsedKarmaConfig.buildWebpack === 'object') {
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        (parsedKarmaConfig.buildWebpack as any).failureCb ??= () => enqueue({ success: false });
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        (parsedKarmaConfig.buildWebpack as any).successCb ??= () => enqueue({ success: true });
-      }
-
       // Close the stream once the Karma server returns.
-      karmaServer = new karma.Server(parsedKarmaConfig as Config, (exitCode) => {
+      karmaServer = new karma.Server(parsedKarmaConfig, (exitCode) => {
         enqueue({ success: exitCode === 0 });
         close();
       });
 
+      karmaServer.on('run_complete', (_, results) => {
+        enqueue({ success: results.exitCode === 0 });
+      });
+
       await karmaServer.start();
     },
     async cancel() {

packages/angular_devkit/build_angular/src/tools/webpack/plugins/karma/karma.ts

@@ -25,8 +25,6 @@ const KARMA_APPLICATION_PATH = '_karma_webpack_';
 let blocked: any[] = [];
 let isBlocked = false;
 let webpackMiddleware: any;
-let successCb: () => void;
-let failureCb: () => void;
 
 const init: any = (config: any, emitter: any) => {
   if (!config.buildWebpack) {
@@ -37,8 +35,6 @@ const init: any = (config: any, emitter: any) => {
   }
   const options = config.buildWebpack.options as BuildOptions;
   const logger: logging.Logger = config.buildWebpack.logger || createConsoleLogger();
-  successCb = config.buildWebpack.successCb;
-  failureCb = config.buildWebpack.failureCb;
 
   // Add a reporter that fixes sourcemap urls.
   if (normalizeSourceMaps(options.sourceMap).scripts) {
@@ -132,9 +128,6 @@ const init: any = (config: any, emitter: any) => {
 
       // Finish Karma run early in case of compilation error.
       emitter.emit('run_complete', [], { exitCode: 1 });
-
-      // Emit a failure build event if there are compilation errors.
-      failureCb();
     }
   });
 
@@ -224,14 +217,6 @@ const eventReporter: any = function (this: any, baseReporterDecorator: any, conf
 
   muteDuplicateReporterLogging(this, config);
 
-  this.onRunComplete = function (_browsers: any, results: any) {
-    if (results.exitCode === 0) {
-      successCb();
-    } else {
-      failureCb();
-    }
-  };
-
   // avoid duplicate failure message
   this.specFailure = () => {};
 };