refactor(@angular/build): simplify library asset resolution and watch handling

Use `resolveAssets` in `collectAssetsToEmit` and reuse collected assets in watch mode instead of running duplicate `picomatch` asset matchers via `checkAssetChanges`.

Author: alan-agius4

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

@@ -225,7 +225,7 @@ async function* runWatchLoop(
   hasModifiedWatchedFile: typeof import('./pipeline/build-action').hasModifiedWatchedFile,
   signal?: AbortSignal,
 ): AsyncIterableIterator<BuilderOutput> {
-  const { checkAssetChanges } = await import('./pipeline/assets');
+  const { collectAssetsToEmit } = await import('./pipeline/assets');
 
   const { workspaceRoot, packageJsonPath, assets, clearScreen } = options;
   const posixPackageJsonPath = toPosixPath(packageJsonPath);
@@ -304,11 +304,13 @@ async function* runWatchLoop(
       buildState.hasEntryPointsChanges ||
       hasModifiedWatchedFile(changedFiles, allWatchedFiles, posixPackageJsonPath);
 
-    if (
-      !hasSourceChanges &&
-      !hasPackageJsonChanges &&
-      !checkAssetChanges(assets, workspaceRoot, changedFiles)
-    ) {
+    const assetsToEmit = await collectAssetsToEmit(
+      assets,
+      workspaceRoot,
+      buildState.hasEmittedAssets ? changedFiles : undefined,
+    );
+
+    if (!hasSourceChanges && !hasPackageJsonChanges && assetsToEmit.length === 0) {
       continue;
     }
 
@@ -322,6 +324,7 @@ async function* runWatchLoop(
         context,
         buildState,
         modifiedFiles: changedFiles,
+        assetsToEmit,
       },
       withProgress,
       watcher,

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

@@ -6,122 +6,36 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { statSync } from 'node:fs';
-import path from 'node:path';
-import picomatch from 'picomatch';
 import { toPosixPath } from '../../../utils/path';
-import { DEFAULT_ASSET_IGNORE, resolveAssets } from '../../../utils/resolve-assets';
+import { resolveAssets } from '../../../utils/resolve-assets';
 import type { NormalizedLibraryOptions } from '../types';
 import { type DiskOutputFile, createDiskOutputFile } from './utils';
 
 /**
- * Resolves and collects configured library assets to be emitted to disk,
- * and registers their source paths with the watch set.
+ * Resolves and collects configured library assets to be emitted to disk.
  *
  * @param assets The normalized asset patterns.
  * @param workspaceRoot The workspace root directory path.
- * @param allWatchedFiles Set collecting all watched file paths for watch mode.
  * @param modifiedFiles Optional set of modified file paths for incremental copying in watch mode.
  * @returns An array of disk file emission descriptors.
  */
 export async function collectAssetsToEmit(
   assets: NormalizedLibraryOptions['assets'],
   workspaceRoot: string,
-  allWatchedFiles: Set<string>,
   modifiedFiles?: ReadonlySet<string>,
 ): Promise<DiskOutputFile[]> {
-  if (assets.length === 0) {
+  if (assets.length === 0 || modifiedFiles?.size === 0) {
     return [];
   }
 
-  if (modifiedFiles) {
-    if (modifiedFiles.size === 0) {
-      return [];
-    }
-
-    const matchers = createAssetMatchers(assets, workspaceRoot);
-    const filesToEmit: DiskOutputFile[] = [];
-
-    for (const file of modifiedFiles) {
-      const resolvedFile = path.isAbsolute(file) ? file : path.resolve(workspaceRoot, file);
-      const posixFile = toPosixPath(resolvedFile);
-
-      for (const { asset, posixInputPrefix, isMatch } of matchers) {
-        if (!posixFile.startsWith(posixInputPrefix)) {
-          continue;
-        }
-
-        const relative = posixFile.slice(posixInputPrefix.length);
-        if (!isMatch(relative)) {
-          continue;
-        }
-
-        if (statSync(resolvedFile, { throwIfNoEntry: false })?.isFile()) {
-          filesToEmit.push(createDiskOutputFile(resolvedFile, path.join(asset.output, relative)));
-          allWatchedFiles.add(posixFile);
-        }
-      }
-    }
-
-    return filesToEmit;
-  }
-
   const resolvedAssets = await resolveAssets(assets, workspaceRoot);
   const filesToEmit: DiskOutputFile[] = [];
 
   for (const { source, destination } of resolvedAssets) {
-    filesToEmit.push(createDiskOutputFile(source, destination));
-    allWatchedFiles.add(toPosixPath(source));
-  }
-
-  return filesToEmit;
-}
-
-/**
- * Checks whether any configured library assets were modified.
- *
- * @param assets The normalized asset patterns.
- * @param workspaceRoot The workspace root directory path.
- * @param changedFiles Set of changed file paths.
- * @returns True if any asset file was modified.
- */
-export function checkAssetChanges(
-  assets: NormalizedLibraryOptions['assets'],
-  workspaceRoot: string,
-  changedFiles: ReadonlySet<string>,
-): boolean {
-  if (assets.length === 0 || changedFiles.size === 0) {
-    return false;
-  }
-
-  const matchers = createAssetMatchers(assets, workspaceRoot);
-
-  for (const file of changedFiles) {
-    const resolvedFile = path.isAbsolute(file) ? file : path.resolve(workspaceRoot, file);
-    const posixFile = toPosixPath(resolvedFile);
-
-    for (const { posixInputPrefix, isMatch } of matchers) {
-      if (posixFile.startsWith(posixInputPrefix)) {
-        const relative = posixFile.slice(posixInputPrefix.length);
-        if (isMatch(relative)) {
-          return true;
-        }
-      }
+    if (!modifiedFiles || modifiedFiles.has(toPosixPath(source))) {
+      filesToEmit.push(createDiskOutputFile(source, destination));
     }
   }
 
-  return false;
-}
-
-function createAssetMatchers(assets: NormalizedLibraryOptions['assets'], workspaceRoot: string) {
-  return assets.map((asset) => {
-    const absInput = path.resolve(workspaceRoot, asset.input);
-    const posixInput = toPosixPath(absInput).replace(/\/+$/, '');
-    const isMatch = picomatch(asset.glob, {
-      dot: true,
-      ignore: [...DEFAULT_ASSET_IGNORE, ...(asset.ignore ?? [])],
-    });
-
-    return { asset, posixInputPrefix: `${posixInput}/`, isMatch };
-  });
+  return filesToEmit;
 }

packages/angular/build/src/builders/library/pipeline/build-action.ts

@@ -17,7 +17,7 @@ import { type BundleEntryPointInput, bundleEntryPoints } from './bundler';
 import { compileLibrary } from './compilation';
 import { generatePackageManifests } from './package-manifests';
 import type { createComponentStylesheetBundlerForLibrary } from './stylesheet-bundler';
-import type { OutputFile } from './utils';
+import type { DiskOutputFile, OutputFile } from './utils';
 
 /**
  * Creates a fresh {@link SingleBuildState} instance.
@@ -42,6 +42,7 @@ export interface BuildActionContext {
   allWatchedFiles: Set<string>;
   buildState: SingleBuildState;
   modifiedFiles?: Set<string>;
+  assetsToEmit?: DiskOutputFile[];
 }
 
 /**
@@ -60,6 +61,7 @@ export async function buildAction(actionContext: BuildActionContext): Promise<vo
     allWatchedFiles,
     buildState,
     modifiedFiles,
+    assetsToEmit,
   } = actionContext;
 
   const posixPackageJsonPath = toPosixPath(options.packageJsonPath);
@@ -170,14 +172,17 @@ export async function buildAction(actionContext: BuildActionContext): Promise<vo
     filesToEmit.push(...generatePackageManifests(options, isWatchMode));
   }
 
-  filesToEmit.push(
-    ...(await collectAssetsToEmit(
+  const resolvedAssetsToEmit =
+    assetsToEmit ??
+    (await collectAssetsToEmit(
       options.assets,
       options.workspaceRoot,
-      allWatchedFiles,
       buildState.hasEmittedAssets ? modifiedFiles : undefined,
-    )),
-  );
+    ));
+  for (const asset of resolvedAssetsToEmit) {
+    allWatchedFiles.add(toPosixPath(asset.source));
+  }
+  filesToEmit.push(...resolvedAssetsToEmit);
 
   await emitFilesToDisk<OutputFile>(filesToEmit, async (file) => {
     const fullFilePath = path.join(options.outputPath, file.path);

packages/angular/build/src/utils/resolve-assets.ts

@@ -13,7 +13,7 @@ import { isSubDirectory } from './path';
 /**
  * Default glob ignore patterns for assets.
  */
-export const DEFAULT_ASSET_IGNORE = ['.gitkeep', '**/.DS_Store', '**/Thumbs.db'] as const;
+const DEFAULT_ASSET_IGNORE = ['.gitkeep', '**/.DS_Store', '**/Thumbs.db'] as const;
 
 export async function resolveAssets(
   entries: {