fix(@angular/build): enhance build logs and output location for library builder

Align library builder logs with the application builder format by logging:
- `Library bundle generation complete. [X seconds] - <timestamp>` on build completion
- `Output location: <outputPath>` for successful builds
- `Watch mode enabled. Watching for file changes...` after initial build when watch mode is active

Author: alan-agius4

packages/angular/build/src/builders/library/builder.ts

@@ -118,10 +118,6 @@ export async function* executeLibraryBuilder(
     }
 
     if (isWatchMode) {
-      if (progress) {
-        logger.info('Watch mode enabled. Watching for file changes...');
-      }
-
       const { setupWatcher } = await import('../../utils/watcher');
       watcher = await setupWatcher({
         workspaceRoot,
@@ -158,6 +154,10 @@ export async function* executeLibraryBuilder(
       return;
     }
 
+    if (progress) {
+      logger.info('Watch mode enabled. Watching for file changes...');
+    }
+
     yield* runWatchLoop(
       watcher,
       normalizedOptions,
@@ -190,11 +190,11 @@ async function executeBuild(
   buildAction: typeof import('./pipeline/build-action').buildAction,
 ): Promise<BuilderOutput> {
   const startTime = process.hrtime.bigint();
-  const { context, watchedCompilationFiles, isWatchMode } = actionContext;
+  const { context, watchedCompilationFiles, isWatchMode, options } = actionContext;
 
   try {
     await withProgress(message, () => buildAction(actionContext));
-    logBuildResult(context.logger, startTime, true);
+    logBuildResult(context.logger, startTime, true, options.outputPath);
     if (isWatchMode) {
       logCumulativeDurations();
     }
@@ -343,14 +343,23 @@ async function* runWatchLoop(
 /**
  * Logs the build completion time and status.
  */
-function logBuildResult(logger: logging.LoggerApi, startTime: bigint, success: boolean): void {
-  const durationMs = Number(process.hrtime.bigint() - startTime) / 1_000_000;
-  const durationSec = (durationMs / 1000).toFixed(2);
+function logBuildResult(
+  logger: logging.LoggerApi,
+  startTime: bigint,
+  success: boolean,
+  outputPath?: string,
+): void {
+  const buildTime = Number(process.hrtime.bigint() - startTime) / 10 ** 9;
+  const message =
+    `Library bundle generation ${success ? 'complete' : 'failed'}.` +
+    ` [${buildTime.toFixed(3)} seconds] - ${new Date().toISOString()}`;
 
   if (success) {
-    logger.info(`Build at: ${new Date().toISOString()} - Time: ${durationMs.toFixed(0)}ms`);
-    logger.info(`Built Angular library in ${durationSec}s.`);
+    logger.info(message);
+    if (outputPath) {
+      logger.info(`Output location: ${outputPath}\n`);
+    }
   } else {
-    logger.error(`Build failed after ${durationSec}s.`);
+    logger.error(message);
   }
 }

packages/angular/build/src/builders/library/tests/behavior/build_spec.ts

@@ -139,5 +139,55 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
         tslib: '^2.0.0',
       });
     });
+
+    it('should log completion and output location', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result, logs } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+      expect(logs).toContain(
+        jasmine.objectContaining({
+          level: 'info',
+          message: jasmine.stringMatching(
+            /Library bundle generation complete\. \[\d+\.\d{3} seconds\] - \d{4}-\d{2}-\d{2}T/,
+          ),
+        }),
+      );
+      expect(logs).toContain(
+        jasmine.objectContaining({
+          level: 'info',
+          message: jasmine.stringMatching(/Output location: .*dist[/\\]lib/),
+        }),
+      );
+    });
+
+    it('should log failure on build error', async () => {
+      await harness.writeFile(
+        'projects/lib/src/public-api.ts',
+        `export const title: number = 'invalid type';`,
+      );
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result, logs } = await harness.executeOnce();
+      expect(result?.success).toBeFalse();
+      expect(logs).toContain(
+        jasmine.objectContaining({
+          level: 'error',
+          message: jasmine.stringMatching(
+            /Library bundle generation failed\. \[\d+\.\d{3} seconds\] - \d{4}-\d{2}-\d{2}T/,
+          ),
+        }),
+      );
+      expect(logs).not.toContain(
+        jasmine.objectContaining({
+          message: jasmine.stringMatching(/Output location:/),
+        }),
+      );
+    });
   });
 });