perf(@angular/cli): optimize package manager discovery with stat-based probing

packages/angular/cli/src/package-managers/discovery.ts

@@ -21,18 +21,6 @@ import {
   SUPPORTED_PACKAGE_MANAGERS,
 } from './package-manager-descriptor';
 
-/**
- * A map from lockfile names to their corresponding package manager.
- * This is a performance optimization to avoid iterating over all possible
- * lockfiles in every directory.
- */
-const LOCKFILE_TO_PACKAGE_MANAGER = new Map<string, PackageManagerName>();
-for (const [name, descriptor] of Object.entries(SUPPORTED_PACKAGE_MANAGERS)) {
-  for (const lockfile of descriptor.lockfiles) {
-    LOCKFILE_TO_PACKAGE_MANAGER.set(lockfile, name as PackageManagerName);
-  }
-}
-
 /**
  * Searches a directory for lockfiles and returns a set of package managers that correspond to them.
  * @param host A `Host` instance for interacting with the file system.
@@ -47,25 +35,32 @@ async function findLockfiles(
 ): Promise<Set<PackageManagerName>> {
   logger?.debug(`Searching for lockfiles in '${directory}'...`);
 
-  try {
-    const files = await host.readdir(directory);
-    const foundPackageManagers = new Set<PackageManagerName>();
-
-    for (const file of files) {
-      const packageManager = LOCKFILE_TO_PACKAGE_MANAGER.get(file);
-      if (packageManager) {
-        logger?.debug(`  Found '${file}'.`);
-        foundPackageManagers.add(packageManager);
-      }
+  const foundPackageManagers = new Set<PackageManagerName>();
+  const checks: Promise<void>[] = [];
+
+  for (const [name, descriptor] of Object.entries(SUPPORTED_PACKAGE_MANAGERS)) {
+    const manager = name as PackageManagerName;
+    for (const lockfile of descriptor.lockfiles) {
+      checks.push(
+        (async () => {
+          try {
+            const path = join(directory, lockfile);
+            const stats = await host.stat(path);
+            if (stats.isFile()) {
+              logger?.debug(`  Found '${lockfile}'.`);
+              foundPackageManagers.add(manager);
+            }
+          } catch {
+            // File does not exist or cannot be accessed.
+          }
+        })(),
+      );
     }
+  }
 
-    return foundPackageManagers;
-  } catch (e) {
-    logger?.debug(`  Failed to read directory: ${e}`);
+  await Promise.all(checks);
 
-    // Ignore directories that don't exist or can't be read.
-    return new Set();
-  }
+  return foundPackageManagers;
 }
 
 /**

packages/angular/cli/src/package-managers/discovery_spec.ts

@@ -64,14 +64,6 @@ describe('discover', () => {
     expect(result).toBeNull();
   });
 
-  it('should handle file system errors during readdir gracefully', async () => {
-    const host = new MockHost({});
-    host.readdir = () => Promise.reject(new Error('Permission denied'));
-
-    const result = await discover(host, '/project');
-    expect(result).toBeNull();
-  });
-
   it('should handle file system errors during stat gracefully', async () => {
     const host = new MockHost({ '/project': ['.git'] });
     host.stat = () => Promise.reject(new Error('Permission denied'));

packages/angular/cli/src/package-managers/host.ts

@@ -39,13 +39,6 @@ export interface Host {
    */
   stat(path: string): Promise<Stats>;
 
-  /**
-   * Reads the contents of a directory.
-   * @param path The path to the directory.
-   * @returns A promise that resolves to an array of file and directory names.
-   */
-  readdir(path: string): Promise<string[]>;
-
   /**
    * Reads the content of a file.
    * @param path The path to the file.
@@ -108,7 +101,6 @@ export interface Host {
  */
 export const NodeJS_HOST: Host = {
   stat,
-  readdir,
   mkdir,
   readFile: (path: string) => readFile(path, { encoding: 'utf8' }),
   copyFile: (src, dest) => copyFile(src, dest, constants.COPYFILE_FICLONE),

packages/angular/cli/src/package-managers/testing/mock-host.ts

@@ -19,7 +19,16 @@ export class MockHost implements Host {
   constructor(files: Record<string, string[] | true> = {}) {
     // Normalize paths to use forward slashes for consistency in tests.
     for (const [path, content] of Object.entries(files)) {
-      this.fs.set(path.replace(/\\/g, '/'), content);
+      const normalizedPath = path.replace(/\\/g, '/');
+      this.fs.set(normalizedPath, content);
+
+      // If the content is an array (directory listing), create entries for the files in it.
+      if (Array.isArray(content)) {
+        for (const file of content) {
+          const filePath = normalizedPath === '/' ? `/${file}` : `${normalizedPath}/${file}`;
+          this.fs.set(filePath, []); // Use empty array to represent a file (not `true` which is a dir)
+        }
+      }
     }
   }
 
@@ -34,17 +43,11 @@ export class MockHost implements Host {
     }
 
     // A `true` value signifies a directory in our mock file system.
-    return Promise.resolve({ isDirectory: () => content === true } as Stats);
-  }
-
-  readdir(path: string): Promise<string[]> {
-    const content = this.fs.get(path.replace(/\\/g, '/'));
-    if (content === true || content === undefined) {
-      // This should be a directory with a file list.
-      return Promise.reject(new Error(`Directory not found or not a directory: ${path}`));
-    }
-
-    return Promise.resolve(content);
+    // Anything else is considered a file for the purpose of this mock.
+    return Promise.resolve({
+      isDirectory: () => content === true,
+      isFile: () => content !== true,
+    } as Stats);
   }
 
   runCommand(): Promise<{ stdout: string; stderr: string }> {