chore: import upstream snapshot with attribution

__tests__/installer.test.ts

@@ -0,0 +1,104 @@
+/**
+ * Installer Tests
+ *
+ * Tests for installer config-writer fixes:
+ * - readJsonFile error handling
+ *
+ * (The CLAUDE.md instructions block is no longer written — see issue
+ * #529. The marker-based install/uninstall self-heal is covered in
+ * `installer-targets.test.ts`.)
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+
+// We test the exported functions from config-writer
+import {
+  writeMcpConfig,
+} from '../src/installer/config-writer';
+
+function createTempDir(): string {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-installer-test-'));
+}
+
+function cleanupTempDir(dir: string): void {
+  if (fs.existsSync(dir)) {
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+}
+
+describe('Installer Config Writer', () => {
+  let origCwd: string;
+  let tempDir: string;
+
+  beforeEach(() => {
+    tempDir = createTempDir();
+    origCwd = process.cwd();
+    process.chdir(tempDir);
+  });
+
+  afterEach(() => {
+    process.chdir(origCwd);
+    cleanupTempDir(tempDir);
+  });
+
+  describe('readJsonFile error handling', () => {
+    it('should return empty object for non-existent file', () => {
+      // writeMcpConfig reads .mcp.json - if it doesn't exist, it should create it
+      writeMcpConfig('local');
+
+      const mcpJson = path.join(tempDir, '.mcp.json');
+      expect(fs.existsSync(mcpJson)).toBe(true);
+
+      const content = JSON.parse(fs.readFileSync(mcpJson, 'utf-8'));
+      expect(content.mcpServers).toBeDefined();
+      expect(content.mcpServers.codegraph).toBeDefined();
+    });
+
+    it('should handle corrupted JSON by creating backup', () => {
+      // Create a corrupted .mcp.json
+      const mcpJson = path.join(tempDir, '.mcp.json');
+      fs.writeFileSync(mcpJson, '{ this is not valid json !!!');
+
+      // Suppress console.warn during test
+      const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+      // Should not throw - gracefully handles corruption
+      writeMcpConfig('local');
+
+      // Should have warned
+      expect(warnSpy).toHaveBeenCalled();
+      const warnMsg = warnSpy.mock.calls[0][0];
+      expect(warnMsg).toContain('Warning');
+
+      // Backup should exist
+      expect(fs.existsSync(mcpJson + '.backup')).toBe(true);
+      // Original backup content should be the corrupted content
+      const backup = fs.readFileSync(mcpJson + '.backup', 'utf-8');
+      expect(backup).toContain('this is not valid json');
+
+      // New file should be valid JSON with codegraph config
+      const content = JSON.parse(fs.readFileSync(mcpJson, 'utf-8'));
+      expect(content.mcpServers.codegraph).toBeDefined();
+
+      warnSpy.mockRestore();
+    });
+
+    it('should preserve existing valid config when adding codegraph', () => {
+      const mcpJson = path.join(tempDir, '.mcp.json');
+      fs.writeFileSync(mcpJson, JSON.stringify({
+        mcpServers: { other: { command: 'other-tool' } },
+        customField: 'preserved',
+      }, null, 2));
+
+      writeMcpConfig('local');
+
+      const content = JSON.parse(fs.readFileSync(mcpJson, 'utf-8'));
+      expect(content.mcpServers.codegraph).toBeDefined();
+      expect(content.mcpServers.other).toBeDefined();
+      expect(content.customField).toBe('preserved');
+    });
+  });
+});