chore: upgrade vitest to v4 (#1115)

* chore: upgrade vitest to v4 and fix breaking test changes

Upgrade vitest from v2 to v4.1.4 across all packages, and
vitest-mock-extended from v3 to v4.0.0. Fix constructor mock
tests that used arrow functions (now require function/class
keyword in Vitest 4) and explicit fs mock factory for Node
built-in auto-mocking changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: add CHANGELOG entry for vitest v4 upgrade

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* changelog

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: brendan-kellam

packages/backend/package.json

@@ -19,7 +19,7 @@
         "tsc-watch": "^6.2.0",
         "tsx": "^4.19.1",
         "typescript": "^5.6.2",
-        "vitest": "^2.1.9"
+        "vitest": "^4.1.4"
     },
     "dependencies": {
         "@coderabbitai/bitbucket": "^1.1.3",

packages/backend/src/repoIndexManager.test.ts

@@ -90,15 +90,19 @@ const mockWorkerClose = vi.fn().mockResolvedValue(undefined);
 const mockWorkerOn = vi.fn();
 
 vi.mock('bullmq', () => ({
-    Queue: vi.fn().mockImplementation(() => ({
-        add: mockQueueAdd,
-        close: mockQueueClose,
-    })),
-    Worker: vi.fn().mockImplementation((_name: string, processor: unknown) => ({
-        on: mockWorkerOn,
-        close: mockWorkerClose,
-        processJob: processor,
-    })),
+    Queue: vi.fn().mockImplementation(function () {
+        return {
+            add: mockQueueAdd,
+            close: mockQueueClose,
+        };
+    }),
+    Worker: vi.fn().mockImplementation(function (_name: string, processor: unknown) {
+        return {
+            on: mockWorkerOn,
+            close: mockWorkerClose,
+            processJob: processor,
+        };
+    }),
     DelayedError: class DelayedError extends Error {
         constructor(message: string) {
             super(message);
@@ -110,9 +114,11 @@ vi.mock('bullmq', () => ({
 // Mock Redlock
 const mockRedlockUsing = vi.fn();
 vi.mock('redlock', () => ({
-    default: vi.fn().mockImplementation(() => ({
-        using: mockRedlockUsing,
-    })),
+    default: vi.fn().mockImplementation(function () {
+        return {
+            using: mockRedlockUsing,
+        };
+    }),
     ExecutionError: class ExecutionError extends Error {
         constructor(message: string) {
             super(message);

packages/queryLanguage/package.json

@@ -11,7 +11,7 @@
         "@lezer/generator": "^1.8.0",
         "tsx": "^4.19.1",
         "typescript": "^5.7.3",
-        "vitest": "^2.1.9"
+        "vitest": "^4.1.4"
     },
     "dependencies": {
         "@lezer/common": "^1.3.0",

packages/shared/package.json

@@ -31,7 +31,7 @@
         "tsc-watch": "6.2.1",
         "tsx": "^4.19.1",
         "typescript": "^5.7.3",
-        "vitest": "^2.1.9"
+        "vitest": "^4.1.4"
     },
     "exports": {
         ".": "./dist/index.server.js",

packages/web/package.json

@@ -227,8 +227,8 @@
     "typescript": "^5",
     "typescript-eslint": "^8.56.1",
     "vite-tsconfig-paths": "^5.1.3",
-    "vitest": "^2.1.5",
-    "vitest-mock-extended": "^3.1.0"
+    "vitest": "^4.1.4",
+    "vitest-mock-extended": "^4.0.0"
   },
   "resolutions": {
     "@types/react": "19.2.14",

packages/web/src/features/git/listCommitsApi.test.ts

@@ -4,7 +4,9 @@ import * as dateUtils from './dateUtils';
 
 // Mock dependencies
 vi.mock('simple-git');
-vi.mock('fs');
+vi.mock('fs', () => ({
+    existsSync: vi.fn().mockReturnValue(true),
+}));
 vi.mock('@sourcebot/shared', () => ({
     REPOS_CACHE_DIR: '/mock/cache/dir',
     getRepoPath: (repo: { id: number }) => ({