From 1ba52b9eaa435c908c50c02727f8b3a6fd351649 Mon Sep 17 00:00:00 2001
From: Jochen Schoubben <jochen.schoubben@digipolis.be>
Date: Tue, 13 Jul 2021 22:41:33 +0200
Subject: [PATCH 1/3] Add options object with ignore property to modern
 useFakeTimers function

---
 examples/async/__tests__/user.test.js         |  6 +++++
 .../src/__tests__/modernFakeTimers.test.ts    | 24 +++++++++++++++++++
 .../jest-fake-timers/src/modernFakeTimers.ts  | 14 +++++++----
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/examples/async/__tests__/user.test.js b/examples/async/__tests__/user.test.js
index a81de93b1cd4..b39d023b5079 100644
--- a/examples/async/__tests__/user.test.js
+++ b/examples/async/__tests__/user.test.js
@@ -68,3 +68,9 @@ it('tests error with async/await and rejects', async () => {
     error: 'User with 3 not found.',
   });
 });
+
+it('works with fakeTimers', async () => {
+  jest.useFakeTimers('modern', {ignore: ['nextTick']});
+  expect.assertions(1);
+  return user.getUserName(4).then(data => expect(data).toEqual('Mark'));
+});
diff --git a/packages/jest-fake-timers/src/__tests__/modernFakeTimers.test.ts b/packages/jest-fake-timers/src/__tests__/modernFakeTimers.test.ts
index a731c594104c..3f3d720fdacf 100644
--- a/packages/jest-fake-timers/src/__tests__/modernFakeTimers.test.ts
+++ b/packages/jest-fake-timers/src/__tests__/modernFakeTimers.test.ts
@@ -798,6 +798,30 @@ describe('FakeTimers', () => {
       expect(global.setImmediate).not.toBe(nativeSetImmediate);
       expect(global.clearImmediate).not.toBe(nativeClearImmediate);
     });
+
+    it('ignores timer functions from the ignore option', () => {
+      const nativeSetTimeout = jest.fn();
+      const nativeClearTimeout = jest.fn();
+      const nativeNextTick = jest.fn();
+      process.nextTick = nativeNextTick;
+      const global = {
+        Date,
+        clearTimeout: nativeClearTimeout,
+        process,
+        setTimeout: nativeSetTimeout,
+      };
+
+      const timers = new FakeTimers({global});
+      timers.useFakeTimers({
+        ignore: ['nextTick', 'clearTimeout'],
+      });
+
+      // Ignored functions don't get mocked
+      expect(global.process.nextTick).toBe(nativeNextTick);
+      expect(global.clearTimeout).toBe(nativeClearTimeout);
+      // check if other functions are still being mocked
+      expect(global.setTimeout).not.toBe(nativeSetTimeout);
+    });
   });
 
   describe('getTimerCount', () => {
diff --git a/packages/jest-fake-timers/src/modernFakeTimers.ts b/packages/jest-fake-timers/src/modernFakeTimers.ts
index 80cd292a69be..8b38315c0ad5 100644
--- a/packages/jest-fake-timers/src/modernFakeTimers.ts
+++ b/packages/jest-fake-timers/src/modernFakeTimers.ts
@@ -12,6 +12,10 @@ import {
 } from '@sinonjs/fake-timers';
 import {StackTraceConfig, formatStackTrace} from 'jest-message-util';
 
+interface ModernFakeTimersOptions {
+  ignore?: Array<string>;
+}
+
 export default class FakeTimers {
   private _clock!: InstalledClock;
   private _config: StackTraceConfig;
@@ -93,11 +97,13 @@ export default class FakeTimers {
     }
   }
 
-  useFakeTimers(): void {
+  useFakeTimers(options: ModernFakeTimersOptions = {}): void {
     if (!this._fakingTime) {
-      const toFake = Object.keys(this._fakeTimers.timers) as Array<
-        keyof FakeTimerWithContext['timers']
-      >;
+      const toFake = Object.keys(this._fakeTimers.timers).filter(
+        // This is a simple attempt to fix the issue when using fakeTimers in combination with promises
+        // Developers can now add the nextTick function to the list timers not to mock
+        timerFunc => !(options?.ignore || []).includes(timerFunc),
+      ) as Array<keyof FakeTimerWithContext['timers']>;
 
       this._clock = this._fakeTimers.install({
         loopLimit: this._maxLoops,

From c94b638b9350b55929fc9b1b10ef4b1f5582e2d7 Mon Sep 17 00:00:00 2001
From: Jochen Schoubben <jochen.schoubben@digipolis.be>
Date: Tue, 13 Jul 2021 22:45:25 +0200
Subject: [PATCH 2/3] Added changelog entry

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6b1d88a6a8d..7f8dc8ed88d5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## master
 
 ### Features
+- `[@jest/fake-timers]` Add options object with ignore property to modern useFakeTimers function. ([#11661](https://github.com/facebook/jest/pull/11661))
 
 ### Fixes
 

From 569028af5f6398c30c8b3710deef86ae715bbf67 Mon Sep 17 00:00:00 2001
From: Jochen Schoubben <jochen.schoubben@digipolis.be>
Date: Wed, 14 Jul 2021 00:34:53 +0200
Subject: [PATCH 3/3] Removed example code because it fails the tests

---
 examples/async/__tests__/user.test.js | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/examples/async/__tests__/user.test.js b/examples/async/__tests__/user.test.js
index b39d023b5079..a81de93b1cd4 100644
--- a/examples/async/__tests__/user.test.js
+++ b/examples/async/__tests__/user.test.js
@@ -68,9 +68,3 @@ it('tests error with async/await and rejects', async () => {
     error: 'User with 3 not found.',
   });
 });
-
-it('works with fakeTimers', async () => {
-  jest.useFakeTimers('modern', {ignore: ['nextTick']});
-  expect.assertions(1);
-  return user.getUserName(4).then(data => expect(data).toEqual('Mark'));
-});