fix(@angular/build): align library watch asset matching with initial build and deduplicate outputs

- Respect `asset.followSymlinks` in watch mode by using `lstatSync` when `!asset.followSymlinks` and `statSync` when `asset.followSymlinks` is `true`.
- Normalize `asset.glob` and `asset.ignore` patterns in `createAssetMatchers` to match `tinyglobby` semantics (stripping trailing slashes, expanding directory patterns with `/**`, normalizing POSIX paths, skipping empty strings, and passing `windows: false`).
- Deduplicate collected and resolved assets by destination `path` so later asset configurations override earlier ones without concurrent `fs.cp` operations to the same output destination.
- Queue nested emitted assets for deletion when a deleted parent directory is reported in watch mode.

Author: alan-agius4

packages/angular/build/src/builders/library/pipeline/assets.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { statSync } from 'node:fs';
+import { lstatSync, statSync } from 'node:fs';
 import path from 'node:path';
 import picomatch from 'picomatch';
 import type { NormalizedAssetsPattern } from '../../../utils';
@@ -38,6 +38,22 @@ export interface AssetMatcher {
   isMatch: picomatch.Matcher;
 }
 
+/**
+ * Normalizes a glob pattern to match `tinyglobby` semantics by stripping trailing slashes,
+ * expanding directory patterns with `/**`, and normalizing POSIX segments.
+ *
+ * @param pattern The raw glob pattern string.
+ * @returns The normalized POSIX glob pattern.
+ */
+function normalizeGlobPattern(pattern: string): string {
+  let result = pattern.endsWith('/') ? pattern.slice(0, -1) : pattern;
+  if (pattern.endsWith('/') || !picomatch.scan(result).isGlob) {
+    result += '/**';
+  }
+
+  return path.posix.normalize(result);
+}
+
 /**
  * Compiles picomatch matchers and POSIX input prefixes for each asset configuration.
  *
@@ -46,9 +62,13 @@ export interface AssetMatcher {
  */
 export function createAssetMatchers(assets: NormalizedAssetsPattern[]): readonly AssetMatcher[] {
   return assets.map((asset) => {
-    const isMatch = picomatch(asset.glob, {
+    const ignore = [...DEFAULT_ASSET_IGNORE, ...(asset.ignore ?? [])]
+      .filter((pattern) => pattern.length > 0)
+      .map(normalizeGlobPattern);
+    const isMatch = picomatch(asset.glob ? path.posix.normalize(asset.glob) : [], {
       dot: true,
-      ignore: [...DEFAULT_ASSET_IGNORE, ...(asset.ignore ?? [])],
+      windows: false,
+      ignore,
     });
     const prefix = asset.input.endsWith('/') ? asset.input : `${asset.input}/`;
 
@@ -79,21 +99,32 @@ export async function collectAssetsToEmit(
 
   if (modifiedFiles) {
     const matchers = assetMatchers ?? createAssetMatchers(assets);
-    const filesToEmit: DiskOutputFile[] = [];
-    const filesToDelete: string[] = [];
+    const filesToEmit = new Map<string, { file: DiskOutputFile; matcherIndex: number }>();
+    const filesToDelete = new Set<string>();
 
     for (const file of modifiedFiles) {
-      let isFile: boolean | undefined;
-
-      if (emittedAssets.has(file)) {
-        isFile = statSync(file, { throwIfNoEntry: false })?.isFile() ?? false;
-        if (!isFile) {
-          filesToDelete.push(file);
+      let isFileStat: boolean | undefined;
+      let isFileLstat: boolean | undefined;
+
+      if (!emittedAssets.has(file) && emittedAssets.size > 0) {
+        const dirPrefix = file.endsWith('/') ? file : `${file}/`;
+        let isDeletedDir: boolean | undefined;
+        for (const emittedFile of emittedAssets.keys()) {
+          if (emittedFile.startsWith(dirPrefix)) {
+            if (!(isDeletedDir ??= !statSync(file, { throwIfNoEntry: false })?.isDirectory())) {
+              break;
+            }
+            filesToDelete.add(emittedFile);
+          }
+        }
+        if (isDeletedDir !== undefined) {
           continue;
         }
       }
 
-      for (const { asset, prefix, isMatch } of matchers) {
+      let matched = false;
+      for (let matcherIndex = 0; matcherIndex < matchers.length; matcherIndex++) {
+        const { asset, prefix, isMatch } = matchers[matcherIndex];
         if (!file.startsWith(prefix)) {
           continue;
         }
@@ -103,24 +134,41 @@ export async function collectAssetsToEmit(
           continue;
         }
 
-        isFile ??= statSync(file, { throwIfNoEntry: false })?.isFile() ?? false;
+        const isFile = asset.followSymlinks
+          ? (isFileStat ??= statSync(file, { throwIfNoEntry: false })?.isFile() ?? false)
+          : (isFileLstat ??= lstatSync(file, { throwIfNoEntry: false })?.isFile() ?? false);
         if (!isFile) {
-          break;
+          continue;
         }
 
-        filesToEmit.push(createDiskOutputFile(file, path.posix.join(asset.output, relative)));
+        matched = true;
+        const outputFile = createDiskOutputFile(file, path.posix.join(asset.output, relative));
+        const existing = filesToEmit.get(outputFile.path);
+        if (!existing || matcherIndex >= existing.matcherIndex) {
+          filesToEmit.set(outputFile.path, { file: outputFile, matcherIndex });
+        }
+      }
+
+      if (emittedAssets.has(file) && !matched) {
+        filesToDelete.add(file);
       }
     }
 
-    return { filesToEmit, filesToDelete };
+    return {
+      filesToEmit: Array.from(filesToEmit.values(), ({ file }) => file),
+      filesToDelete: Array.from(filesToDelete),
+    };
   }
 
   const resolvedAssets = await resolveAssets(assets, workspaceRoot);
+  const filesToEmit = new Map<string, DiskOutputFile>();
+  for (const { source, destination } of resolvedAssets) {
+    const outputFile = createDiskOutputFile(source, destination);
+    filesToEmit.set(outputFile.path, outputFile);
+  }
 
   return {
-    filesToEmit: resolvedAssets.map(({ source, destination }) =>
-      createDiskOutputFile(source, destination),
-    ),
+    filesToEmit: Array.from(filesToEmit.values()),
     filesToDelete: [],
   };
 }

packages/angular/build/src/builders/library/pipeline/assets_spec.ts

@@ -0,0 +1,179 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import assert from 'node:assert';
+import { mkdir, mkdtemp, rm, symlink, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+import { toPosixPath } from '../../../utils/path';
+import { collectAssetsToEmit, createAssetMatchers } from './assets';
+
+describe('library pipeline assets', () => {
+  let tempRoot: string;
+
+  beforeEach(async () => {
+    const baseTmpDir = process.env['TEST_TMPDIR'];
+    assert(baseTmpDir, 'TEST_TMPDIR is not set');
+    tempRoot = toPosixPath(await mkdtemp(path.join(baseTmpDir, 'angular-cli-assets-spec-')));
+  });
+
+  afterEach(async () => {
+    await rm(tempRoot, { recursive: true, force: true });
+  });
+
+  describe('createAssetMatchers', () => {
+    it('should normalize patterns, expand directories in ignore, and skip empty strings', () => {
+      const matchers = createAssetMatchers([
+        {
+          glob: './**/*.txt',
+          input: `${tempRoot}/assets`,
+          output: 'assets',
+          ignore: ['', 'ignored-dir', './ignored-dir-2/', 'specific.txt'],
+        },
+      ]);
+
+      expect(matchers).toHaveSize(1);
+      const [matcher] = matchers;
+
+      expect(matcher.isMatch('keep.txt')).toBeTrue();
+      expect(matcher.isMatch('nested/keep.txt')).toBeTrue();
+      expect(matcher.isMatch('.hidden.txt')).toBeTrue();
+      expect(matcher.isMatch('specific.txt')).toBeFalse();
+      expect(matcher.isMatch('ignored-dir/file.txt')).toBeFalse();
+      expect(matcher.isMatch('ignored-dir/sub/file.txt')).toBeFalse();
+      expect(matcher.isMatch('ignored-dir-2/file.txt')).toBeFalse();
+      expect(matcher.isMatch('.gitkeep')).toBeFalse();
+      expect(matcher.isMatch('nested/.DS_Store')).toBeFalse();
+    });
+
+    it('should not throw when glob is an empty string', () => {
+      const matchers = createAssetMatchers([
+        {
+          glob: '',
+          input: `${tempRoot}/assets`,
+          output: 'assets',
+        },
+      ]);
+
+      expect(matchers).toHaveSize(1);
+      expect(matchers[0].isMatch('any.txt')).toBeFalse();
+    });
+  });
+
+  describe('collectAssetsToEmit', () => {
+    it('should deduplicate resolved assets by destination path with later patterns overriding earlier ones', async () => {
+      const defaultDir = `${tempRoot}/lib`;
+      const customDir = `${tempRoot}/docs`;
+      await mkdir(defaultDir, { recursive: true });
+      await mkdir(customDir, { recursive: true });
+
+      const defaultReadme = `${defaultDir}/README.md`;
+      const customReadme = `${customDir}/README.md`;
+      await writeFile(defaultReadme, '# Default');
+      await writeFile(customReadme, '# Custom');
+
+      const assets = [
+        { glob: 'README.md', input: defaultDir, output: '.' },
+        { glob: 'README.md', input: customDir, output: '.' },
+      ];
+
+      const initialResult = await collectAssetsToEmit(assets, tempRoot, new Map());
+      expect(initialResult.filesToEmit).toEqual([
+        {
+          origin: 'disk',
+          source: customReadme,
+          path: 'README.md',
+        },
+      ]);
+
+      // Watch mode: even if customReadme appears before defaultReadme in modifiedFiles,
+      // the later asset pattern (customReadme) should still take precedence.
+      const watchResult = await collectAssetsToEmit(
+        assets,
+        tempRoot,
+        new Map(),
+        new Set([customReadme, defaultReadme]),
+      );
+      expect(watchResult.filesToEmit).toEqual([
+        {
+          origin: 'disk',
+          source: customReadme,
+          path: 'README.md',
+        },
+      ]);
+    });
+
+    it('should respect followSymlinks in watch mode', async () => {
+      const assetsDir = `${tempRoot}/assets`;
+      await mkdir(assetsDir, { recursive: true });
+
+      const targetFile = `${tempRoot}/external.txt`;
+      const symlinkFile = `${assetsDir}/linked.txt`;
+      await writeFile(targetFile, 'external');
+      await symlink(targetFile, symlinkFile);
+
+      const assetsNoFollow = [
+        { glob: '**/*.txt', input: assetsDir, output: 'out', followSymlinks: false },
+      ];
+      const noFollowResult = await collectAssetsToEmit(
+        assetsNoFollow,
+        tempRoot,
+        new Map(),
+        new Set([symlinkFile]),
+      );
+      expect(noFollowResult.filesToEmit).toEqual([]);
+
+      const assetsFollow = [
+        { glob: '**/*.txt', input: assetsDir, output: 'out', followSymlinks: true },
+      ];
+      const followResult = await collectAssetsToEmit(
+        assetsFollow,
+        tempRoot,
+        new Map(),
+        new Set([symlinkFile]),
+      );
+      expect(followResult.filesToEmit).toEqual([
+        {
+          origin: 'disk',
+          source: symlinkFile,
+          path: 'out/linked.txt',
+        },
+      ]);
+    });
+
+    it('should queue nested emitted assets for deletion when a deleted directory is reported in watch mode', async () => {
+      const assetsDir = `${tempRoot}/assets`;
+      const subDir = `${assetsDir}/sub`;
+      const keepDir = `${assetsDir}/keep-dir`;
+      await mkdir(keepDir, { recursive: true });
+
+      const nestedFileA = `${subDir}/a.txt`;
+      const nestedFileB = `${subDir}/deep/b.txt`;
+      const keepFile = `${keepDir}/keep.txt`;
+      await writeFile(keepFile, 'keep');
+
+      const emittedAssets = new Map<string, Set<string>>([
+        [nestedFileA, new Set(['out/sub/a.txt'])],
+        [nestedFileB, new Set(['out/sub/deep/b.txt'])],
+        [keepFile, new Set(['out/keep-dir/keep.txt'])],
+      ]);
+
+      const assets = [{ glob: '**/*.txt', input: assetsDir, output: 'out' }];
+
+      // subDir does not exist on disk; keepDir still exists on disk
+      const result = await collectAssetsToEmit(
+        assets,
+        tempRoot,
+        emittedAssets,
+        new Set([subDir, keepDir]),
+      );
+
+      expect(result.filesToEmit).toEqual([]);
+      expect(result.filesToDelete).toEqual([nestedFileA, nestedFileB]);
+    });
+  });
+});