refactor(core): improve ignore resolution and fix directory-matching bug (#23816)

packages/core/src/utils/ignorePathUtils.test.ts

@@ -0,0 +1,129 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import * as path from 'node:path';
+import { getNormalizedRelativePath } from './ignorePathUtils.js';
+
+vi.mock('node:path', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('node:path')>();
+  return {
+    ...actual,
+    resolve: vi.fn(actual.resolve),
+    relative: vi.fn(actual.relative),
+  };
+});
+
+describe('ignorePathUtils', () => {
+  const projectRoot = path.resolve('/work/project');
+
+  it('should return null for invalid inputs', () => {
+    expect(getNormalizedRelativePath(projectRoot, '', false)).toBeNull();
+    expect(
+      getNormalizedRelativePath(projectRoot, null as unknown as string, false),
+    ).toBeNull();
+    expect(
+      getNormalizedRelativePath(
+        projectRoot,
+        undefined as unknown as string,
+        false,
+      ),
+    ).toBeNull();
+  });
+
+  it('should return null for paths outside the project root', () => {
+    expect(
+      getNormalizedRelativePath(projectRoot, '/work/other', false),
+    ).toBeNull();
+    expect(
+      getNormalizedRelativePath(projectRoot, '../outside', false),
+    ).toBeNull();
+  });
+
+  it('should return null for sibling directories with matching prefixes', () => {
+    // If projectRoot is /work/project, /work/project-other should be null
+    expect(
+      getNormalizedRelativePath(
+        projectRoot,
+        '/work/project-other/file.txt',
+        false,
+      ),
+    ).toBeNull();
+  });
+
+  it('should normalize basic relative paths', () => {
+    expect(getNormalizedRelativePath(projectRoot, 'src/index.ts', false)).toBe(
+      'src/index.ts',
+    );
+    expect(
+      getNormalizedRelativePath(projectRoot, './src/index.ts', false),
+    ).toBe('src/index.ts');
+  });
+
+  it('should normalize absolute paths within the root', () => {
+    expect(
+      getNormalizedRelativePath(
+        projectRoot,
+        path.join(projectRoot, 'src/file.ts'),
+        false,
+      ),
+    ).toBe('src/file.ts');
+  });
+
+  it('should enforce trailing slash for directories', () => {
+    expect(getNormalizedRelativePath(projectRoot, 'dist', true)).toBe('dist/');
+    expect(getNormalizedRelativePath(projectRoot, 'dist/', true)).toBe('dist/');
+  });
+
+  it('should NOT add trailing slash for files even if string has one', () => {
+    expect(getNormalizedRelativePath(projectRoot, 'dist/', false)).toBe('dist');
+    expect(getNormalizedRelativePath(projectRoot, 'src/index.ts', false)).toBe(
+      'src/index.ts',
+    );
+  });
+
+  it('should convert Windows backslashes to forward slashes', () => {
+    const winPath = 'src\\components\\Button.tsx';
+    expect(getNormalizedRelativePath(projectRoot, winPath, false)).toBe(
+      'src/components/Button.tsx',
+    );
+
+    const winDir = 'node_modules\\';
+    expect(getNormalizedRelativePath(projectRoot, winDir, true)).toBe(
+      'node_modules/',
+    );
+  });
+
+  it('should handle the project root itself', () => {
+    expect(getNormalizedRelativePath(projectRoot, projectRoot, true)).toBe('/');
+    expect(getNormalizedRelativePath(projectRoot, '.', true)).toBe('/');
+    expect(getNormalizedRelativePath(projectRoot, projectRoot, false)).toBe('');
+    expect(getNormalizedRelativePath(projectRoot, '.', false)).toBe('');
+  });
+
+  it('should remove leading slashes from relative-looking paths', () => {
+    expect(
+      getNormalizedRelativePath(
+        projectRoot,
+        path.join(projectRoot, '/file.ts'),
+        false,
+      ),
+    ).toBe('file.ts');
+  });
+
+  it('should reject Windows cross-drive absolute paths', () => {
+    // Simulate Windows path resolution where cross-drive paths return an
+    // absolute path without "..".
+    vi.spyOn(path, 'resolve').mockImplementation(
+      (...args) => args[args.length - 1],
+    );
+    vi.spyOn(path, 'relative').mockReturnValue('D:\\outside');
+
+    expect(
+      getNormalizedRelativePath('C:\\project', 'D:\\outside', false),
+    ).toBeNull();
+  });
+});