test(@angular/build): prevent flakiness in incremental-watch e2e test

In watch mode, 'Application bundle generation complete.' can be logged before all files have finished being emitted to disk. Sampling 'files.length > 0' initially could capture a partial file count, causing the final count comparison to time out once all assets are fully written.

Update the test to only track JavaScript chunk files (.js), which prevents race conditions with unrelated asset emission and directly aligns with the test's intent of verifying chunk addition and removal for dynamic imports.

Author: alan-agius4

tests/e2e/tests/build/incremental-watch.ts

@@ -7,17 +7,17 @@ import { execAndWaitForOutputToMatch, waitForAnyProcessOutputToMatch } from '../
 
 const buildReadyRegEx = /Application bundle generation complete\./;
 
-async function getOutputFiles(
+async function getOutputChunks(
   dir: string,
-  predicate: (files: string[]) => boolean,
+  predicate: (chunks: string[]) => boolean,
   timeout = 10_000,
 ): Promise<string[]> {
   const start = Date.now();
   while (Date.now() - start < timeout) {
     try {
-      const files = await readdir(dir);
-      if (predicate(files)) {
-        return files;
+      const chunks = (await readdir(dir)).filter((file) => file.endsWith('.js'));
+      if (predicate(chunks)) {
+        return chunks;
       }
     } catch (err: any) {
       if (err?.code !== 'ENOENT') {
@@ -27,10 +27,10 @@ async function getOutputFiles(
     await setTimeout(50);
   }
 
-  const files = await readdir(dir);
-  assert(predicate(files), `Condition not met for files in ${dir}: ${JSON.stringify(files)}`);
+  const chunks = (await readdir(dir)).filter((file) => file.endsWith('.js'));
+  assert(predicate(chunks), `Condition not met for chunks in ${dir}: ${JSON.stringify(chunks)}`);
 
-  return files;
+  return chunks;
 }
 
 export default async function () {
@@ -46,9 +46,9 @@ export default async function () {
     ['build', '--watch', '--configuration=development'],
     buildReadyRegEx,
   );
-  const initialOutputFiles = await getOutputFiles(
+  const initialOutputChunks = await getOutputChunks(
     'dist/test-project/browser',
-    (files) => files.length > 0,
+    (chunks) => chunks.length > 0,
   );
 
   const originalMain = await readFile('src/main.ts');
@@ -66,12 +66,12 @@ export default async function () {
     ),
     appendToFile('src/main.ts', `\nimport('./a').then((m) => m.sayHi());`),
   ]);
-  const intermediateOutputFiles = await getOutputFiles(
+  const intermediateOutputChunks = await getOutputChunks(
     'dist/test-project/browser',
-    (files) => files.length > initialOutputFiles.length,
+    (chunks) => chunks.length > initialOutputChunks.length,
   );
   assert(
-    initialOutputFiles.length < intermediateOutputFiles.length,
+    initialOutputChunks.length < intermediateOutputChunks.length,
     'Additional chunks should be present',
   );
 
@@ -80,13 +80,13 @@ export default async function () {
     waitForAnyProcessOutputToMatch(buildReadyRegEx),
     writeFile('src/main.ts', originalMain),
   ]);
-  const finalOutputFiles = await getOutputFiles(
+  const finalOutputChunks = await getOutputChunks(
     'dist/test-project/browser',
-    (files) => files.length === initialOutputFiles.length,
+    (chunks) => chunks.length === initialOutputChunks.length,
   );
   assert.equal(
-    initialOutputFiles.length,
-    finalOutputFiles.length,
+    initialOutputChunks.length,
+    finalOutputChunks.length,
     'Final chunk count should be equal to initial chunk count.',
   );
 }