test(amplify-cli-core): add tests for packageManager field detection

Add tests for the new findPackageManagerFieldInHierarchy() function
that detects the packageManager field in package.json hierarchy
(corepack convention for monorepos).

New test cases:
- Detect pnpm from packageManager field in package.json
- Detect npm from packageManager field in package.json
- Detect yarn from packageManager field in package.json
- Detect packageManager field from parent directory in hierarchy
- packageManager field takes precedence over lock files
- Falls back to lock file detection when packageManager executable not found

Author: danrivett

packages/amplify-cli-core/src/__tests__/packageManager.test.ts

@@ -1,14 +1,24 @@
 import * as path from 'path';
 import which from 'which';
 import { getPackageManager } from '../utils';
+import * as shellUtils from '../utils/shell-utils';
 
 jest.mock('which');
+jest.mock('../utils/shell-utils');
 
 describe('packageManager tests', () => {
   const baseDirectory = path.join(__dirname, 'testFiles');
   const which_mock = which as jest.Mocked<typeof which>;
-
-  beforeEach(() => jest.clearAllMocks());
+  const shellUtils_mock = shellUtils as jest.Mocked<typeof shellUtils>;
+
+  beforeEach(() => {
+    jest.resetAllMocks();
+    // Default to returning undefined (executable not found)
+    // Tests that need specific executables should set them explicitly
+    (which_mock.sync as jest.Mock).mockReturnValue(undefined);
+    // Mock yarn --version to return a valid version
+    shellUtils_mock.execWithOutputAsString.mockResolvedValue('4.0.0');
+  });
 
   test('returns null when no package.json found', async () => {
     const testDirectory = path.join(baseDirectory, 'packageManager-null');
@@ -19,31 +29,36 @@ describe('packageManager tests', () => {
   });
 
   test('detects yarn2 correctly', async () => {
-    which_mock.sync.mockReturnValue('/path/to/yarn');
+    (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+      if (executable === 'yarn') return '/path/to/yarn';
+      return undefined;
+    });
 
     const testDirectory = path.join(baseDirectory, 'packageManager-yarn2');
 
     const packageManager = await getPackageManager(testDirectory);
 
-    expect(which_mock.sync).toBeCalledTimes(1);
     expect(packageManager).toBeDefined();
     expect(packageManager?.packageManager).toEqual('yarn');
     expect(packageManager?.version?.major).toBeGreaterThanOrEqual(2);
   });
 
   test('detects yarn correctly', async () => {
-    which_mock.sync.mockReturnValue('/path/to/yarn');
+    (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+      if (executable === 'yarn') return '/path/to/yarn';
+      return undefined;
+    });
 
     const testDirectory = path.join(baseDirectory, 'packageManager-yarn');
 
     const packageManager = await getPackageManager(testDirectory);
 
-    expect(which_mock.sync).toBeCalledTimes(1);
     expect(packageManager).toBeDefined();
     expect(packageManager!.packageManager).toEqual('yarn');
   });
 
   test('detects npm correctly', async () => {
+    // No executables in PATH - should fall back to npm via lock file
     const testDirectory = path.join(baseDirectory, 'packageManager-npm');
 
     const packageManager = await getPackageManager(testDirectory);
@@ -53,26 +68,121 @@ describe('packageManager tests', () => {
   });
 
   test('detects yarn fallback correctly when yarn in path', async () => {
-    which_mock.sync.mockReturnValue('/path/to/yarn');
+    (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+      if (executable === 'yarn') return '/path/to/yarn';
+      return undefined;
+    });
 
     const testDirectory = path.join(baseDirectory, 'packageManager-fallback');
 
     const packageManager = await getPackageManager(testDirectory);
 
-    expect(which_mock.sync).toBeCalledTimes(1);
     expect(packageManager).toBeDefined();
     expect(packageManager!.packageManager).toEqual('yarn');
   });
 
   test('detects npm fallback correctly when yarn is not in path', async () => {
-    (which_mock.sync as any).mockReturnValue(undefined);
-
+    // No executables in PATH (already set in beforeEach)
     const testDirectory = path.join(baseDirectory, 'packageManager-fallback');
 
     const packageManager = await getPackageManager(testDirectory);
 
-    expect(which_mock.sync).toBeCalledTimes(2);
     expect(packageManager).toBeDefined();
     expect(packageManager!.packageManager).toEqual('npm');
   });
+
+  describe('packageManager field detection (corepack convention)', () => {
+    test('detects pnpm from packageManager field in package.json', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        if (executable === 'pnpm') return '/path/to/pnpm';
+        return undefined;
+      });
+
+      const testDirectory = path.join(baseDirectory, 'packageManager-pnpm-field');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('pnpm');
+    });
+
+    test('detects npm from packageManager field in package.json', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        if (executable === 'npm') return '/path/to/npm';
+        return undefined;
+      });
+
+      const testDirectory = path.join(baseDirectory, 'packageManager-npm-field');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('npm');
+    });
+
+    test('detects yarn from packageManager field in package.json', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        if (executable === 'yarn') return '/path/to/yarn';
+        return undefined;
+      });
+
+      const testDirectory = path.join(baseDirectory, 'packageManager-yarn-field');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('yarn');
+    });
+
+    test('detects packageManager field from parent directory in hierarchy', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        if (executable === 'pnpm') return '/path/to/pnpm';
+        return undefined;
+      });
+
+      // subdir has package.json but no packageManager field
+      // parent directory has packageManager: pnpm@10.17.0
+      const testDirectory = path.join(baseDirectory, 'packageManager-hierarchy', 'subdir');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('pnpm');
+    });
+
+    test('packageManager field takes precedence over lock files', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        if (executable === 'pnpm') return '/path/to/pnpm';
+        if (executable === 'yarn') return '/path/to/yarn';
+        return undefined;
+      });
+
+      // Directory has yarn.lock but package.json has packageManager: pnpm@10.17.0
+      const testDirectory = path.join(baseDirectory, 'packageManager-field-with-lockfile');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('pnpm');
+    });
+
+    test('falls back to lock file detection when packageManager executable not found', async () => {
+      (which_mock.sync as jest.Mock).mockImplementation((executable: string) => {
+        // pnpm not in PATH, but yarn is
+        if (executable === 'pnpm') return undefined;
+        if (executable === 'yarn') return '/path/to/yarn';
+        return undefined;
+      });
+
+      // Parent directory has packageManager: pnpm but pnpm not in PATH
+      // Subdirectory has yarn.lock (no packageManager field to avoid corepack blocking yarn)
+      // yarn is in PATH, so should fall back to yarn via lock file
+      const testDirectory = path.join(baseDirectory, 'packageManager-hierarchy-fallback', 'subdir');
+
+      const packageManager = await getPackageManager(testDirectory);
+
+      expect(packageManager).toBeDefined();
+      expect(packageManager!.packageManager).toEqual('yarn');
+    });
+  });
 });

packages/amplify-cli-core/src/__tests__/testFiles/packageManager-field-with-lockfile/.gitkeep

@@ -0,0 +1,6 @@
+{
+  "name": "packageManager-field-with-lockfile-test",
+  "version": "1.0.0",
+  "description": "Test package with packageManager field that differs from lock file",
+  "packageManager": "pnpm@10.17.0"
+}

packages/amplify-cli-core/src/__tests__/testFiles/packageManager-field-with-lockfile/package.json

@@ -0,0 +1,2 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1

packages/amplify-cli-core/src/__tests__/testFiles/packageManager-field-with-lockfile/yarn.lock

@@ -0,0 +1,6 @@
+{
+  "name": "packageManager-hierarchy-fallback-test",
+  "version": "1.0.0",
+  "description": "Root package with packageManager field for fallback test",
+  "packageManager": "pnpm@10.17.0"
+}

packages/amplify-cli-core/src/__tests__/testFiles/packageManager-hierarchy-fallback/.gitkeep

@@ -0,0 +1,5 @@
+{
+  "name": "packageManager-hierarchy-fallback-subdir-test",
+  "version": "1.0.0",
+  "description": "Subdirectory with yarn.lock but no packageManager field"
+}

packages/amplify-cli-core/src/__tests__/testFiles/packageManager-hierarchy-fallback/package.json

@@ -0,0 +1,2 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1