fix(@angular/build): copy assets replaced by a rename in watch mode

When an asset is replaced by renaming another file over it, as editors with atomic
save do, the native file watcher on Linux reports the asset as added instead of
modified. The incremental build only copied existing assets that were reported as
modified, so the output kept the previous contents of the asset.

Existing assets reported as added are now copied as well. The new spec disables
polling so that the native watcher is used.

Author: MeAkib

packages/angular/build/src/builders/application/build-action.ts

@@ -321,7 +321,8 @@ function* emitOutputResults(
     if (!previousAssetsInfo.has(destination)) {
       incrementalResult.added.push(destination);
       incrementalResult.background = false;
-    } else if (changes.modified.has(source)) {
+    } else if (changes.modified.has(source) || changes.added.has(source)) {
+      // A file replaced by a rename (e.g. an atomic save) can be reported as added.
       incrementalResult.modified.push(destination);
       incrementalResult.background = false;
     } else {

packages/angular/build/src/builders/application/tests/behavior/rebuild-assets_spec.ts

@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
+import { rename } from 'node:fs/promises';
 import { buildApplication } from '../../index';
 import { APPLICATION_BUILDER_INFO, BASE_OPTIONS, describeBuilder } from '../setup';
 
@@ -43,6 +44,39 @@ describeBuilder(buildApplication, APPLICATION_BUILDER_INFO, (harness) => {
       ]);
     });
 
+    it('emits an asset replaced by renaming another file over it', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        assets: [
+          {
+            glob: '**/*',
+            input: 'public',
+          },
+        ],
+        watch: true,
+        // Polling reports a replaced file as modified, while native watchers can report it as added.
+        poll: undefined,
+      });
+
+      await harness.executeWithCases([
+        async ({ result }) => {
+          expect(result?.success).toBeTrue();
+          harness.expectFile('dist/browser/asset.txt').content.toContain('foo');
+
+          // Editors with atomic save write a temporary file and rename it over the original.
+          await harness.writeFile('asset.txt.tmp', 'bar');
+          await rename(
+            harness.resolvePath('asset.txt.tmp'),
+            harness.resolvePath('public/asset.txt'),
+          );
+        },
+        ({ result }) => {
+          expect(result?.success).toBeTrue();
+          harness.expectFile('dist/browser/asset.txt').content.toContain('bar');
+        },
+      ]);
+    });
+
     it('remove deleted asset from output', async () => {
       await Promise.all([
         harness.writeFile('public/asset-two.txt', 'bar'),