jestFakeTimers.ts

/**
 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {ModuleMocker} from 'jest-mock';
import {formatStackTrace, StackTraceConfig} from 'jest-message-util';

type Callback = (...args: Array<unknown>) => void;

type TimerID = string;

type Tick = {
  uuid: string;
  callback: Callback;
};

type Timer = {
  type: string;
  callback: Callback;
  expiry: number;
  interval?: number;
};

type TimerAPI = {
  clearImmediate: typeof global.clearImmediate;
  clearInterval: typeof global.clearInterval;
  clearTimeout: typeof global.clearTimeout;
  nextTick: typeof process.nextTick;

  setImmediate: typeof global.setImmediate;
  setInterval: typeof global.setInterval;
  setTimeout: typeof global.setTimeout;
};

type TimerConfig<Ref> = {
  idToRef: (id: number) => Ref;
  refToId: (ref: Ref) => number | void;
};

const MS_IN_A_YEAR = 31536000000;

// TODO: Copied from `jest-util` to avoid cyclic dependency. Import from `jest-util` in the next major
const setGlobal = (
  globalToMutate: NodeJS.Global | Window,
  key: string,
  value: unknown,
) => {
  // @ts-ignore: no index
  globalToMutate[key] = value;
};

export default class FakeTimers<TimerRef> {
  private _cancelledTicks!: Record<string, boolean>;
  private _config: StackTraceConfig;
  private _disposed?: boolean;
  private _fakeTimerAPIs!: TimerAPI;
  private _global: NodeJS.Global;
  private _immediates!: Array<Tick>;
  private _maxLoops: number;
  private _moduleMocker: ModuleMocker;
  private _now!: number;
  private _ticks!: Array<Tick>;
  private _timerAPIs: TimerAPI;
  private _timers!: Map<string, Timer>;
  private _uuidCounter: number;
  private _timerConfig: TimerConfig<TimerRef>;

  constructor({
    global,
    moduleMocker,
    timerConfig,
    config,
    maxLoops,
  }: {
    global: NodeJS.Global;
    moduleMocker: ModuleMocker;
    timerConfig: TimerConfig<TimerRef>;
    config: StackTraceConfig;
    maxLoops?: number;
  }) {
    this._global = global;
    this._timerConfig = timerConfig;
    this._config = config;
    this._maxLoops = maxLoops || 100000;
    this._uuidCounter = 1;
    this._moduleMocker = moduleMocker;

    // Store original timer APIs for future reference
    this._timerAPIs = {
      clearImmediate: global.clearImmediate,
      clearInterval: global.clearInterval,
      clearTimeout: global.clearTimeout,
      nextTick: global.process && global.process.nextTick,
      setImmediate: global.setImmediate,
      setInterval: global.setInterval,
      setTimeout: global.setTimeout,
    };

    this.reset();
    this._createMocks();
  }

  clearAllTimers() {
    this._immediates = [];
    this._timers.clear();
  }

  dispose() {
    this._disposed = true;
    this.clearAllTimers();
  }

  reset() {
    this._cancelledTicks = {};
    this._now = 0;
    this._ticks = [];
    this._immediates = [];
    this._timers = new Map();
  }

  runAllTicks() {
    this._checkFakeTimers();
    // Only run a generous number of ticks and then bail.
    // This is just to help avoid recursive loops
    let i;
    for (i = 0; i < this._maxLoops; i++) {
      const tick = this._ticks.shift();

      if (tick === undefined) {
        break;
      }

      if (!this._cancelledTicks.hasOwnProperty(tick.uuid)) {
        // Callback may throw, so update the map prior calling.
        this._cancelledTicks[tick.uuid] = true;
        tick.callback();
      }
    }

    if (i === this._maxLoops) {
      throw new Error(
        'Ran ' +
          this._maxLoops +
          ' ticks, and there are still more! ' +
          "Assuming we've hit an infinite recursion and bailing out...",
      );
    }
  }

  runAllImmediates() {
    this._checkFakeTimers();
    // Only run a generous number of immediates and then bail.
    let i;
    for (i = 0; i < this._maxLoops; i++) {
      const immediate = this._immediates.shift();
      if (immediate === undefined) {
        break;
      }
      this._runImmediate(immediate);
    }

    if (i === this._maxLoops) {
      throw new Error(
        'Ran ' +
          this._maxLoops +
          ' immediates, and there are still more! Assuming ' +
          "we've hit an infinite recursion and bailing out...",
      );
    }
  }

  private _runImmediate(immediate: Tick) {
    this._fakeClearImmediate(immediate.uuid);
    immediate.callback();
  }

  runAllTimers() {
    this._checkFakeTimers();
    this.runAllTicks();
    this.runAllImmediates();

    // Only run a generous number of timers and then bail.
    // This is just to help avoid recursive loops
    let i;
    for (i = 0; i < this._maxLoops; i++) {
      const nextTimerHandle = this._getNextTimerHandle();

      // If there are no more timer handles, stop!
      if (nextTimerHandle === null) {
        break;
      }

      this._runTimerHandle(nextTimerHandle);

      // Some of the immediate calls could be enqueued
      // during the previous handling of the timers, we should
      // run them as well.
      if (this._immediates.length) {
        this.runAllImmediates();
      }

      if (this._ticks.length) {
        this.runAllTicks();
      }
    }

    if (i === this._maxLoops) {
      throw new Error(
        'Ran ' +
          this._maxLoops +
          ' timers, and there are still more! ' +
          "Assuming we've hit an infinite recursion and bailing out...",
      );
    }
  }

  runOnlyPendingTimers() {
    // We need to hold the current shape of `this._timers` because existing
    // timers can add new ones to the map and hence would run more than necessary.
    // See https://github.com/facebook/jest/pull/4608 for details
    const timerEntries = Array.from(this._timers.entries());
    this._checkFakeTimers();
    this._immediates.forEach(this._runImmediate, this);

    timerEntries
      .sort(([, left], [, right]) => left.expiry - right.expiry)
      .forEach(([timerHandle]) => this._runTimerHandle(timerHandle));
  }

  advanceTimersToNextTimer(steps = 1) {
    if (steps < 1) {
      return;
    }
    const nextExpiry = Array.from(this._timers.values()).reduce(
      (minExpiry: number | null, timer: Timer): number => {
        if (minExpiry === null || timer.expiry < minExpiry) return timer.expiry;
        return minExpiry;
      },
      null,
    );
    if (nextExpiry !== null) {
      this.advanceTimersByTime(nextExpiry - this._now);
      this.advanceTimersToNextTimer(steps - 1);
    }
  }

  advanceTimersByTime(msToRun: number) {
    this._checkFakeTimers();
    // Only run a generous number of timers and then bail.
    // This is just to help avoid recursive loops
    let i;
    for (i = 0; i < this._maxLoops; i++) {
      const timerHandle = this._getNextTimerHandle();

      // If there are no more timer handles, stop!
      if (timerHandle === null) {
        break;
      }
      const timerValue = this._timers.get(timerHandle);
      if (timerValue === undefined) {
        break;
      }
      const nextTimerExpiry = timerValue.expiry;
      if (this._now + msToRun < nextTimerExpiry) {
        // There are no timers between now and the target we're running to, so
        // adjust our time cursor and quit
        this._now += msToRun;
        break;
      } else {
        msToRun -= nextTimerExpiry - this._now;
        this._now = nextTimerExpiry;
        this._runTimerHandle(timerHandle);
      }
    }

    if (i === this._maxLoops) {
      throw new Error(
        'Ran ' +
          this._maxLoops +
          ' timers, and there are still more! ' +
          "Assuming we've hit an infinite recursion and bailing out...",
      );
    }
  }

  runWithRealTimers(cb: Callback) {
    const prevClearImmediate = this._global.clearImmediate;
    const prevClearInterval = this._global.clearInterval;
    const prevClearTimeout = this._global.clearTimeout;
    const prevNextTick = this._global.process.nextTick;
    const prevSetImmediate = this._global.setImmediate;
    const prevSetInterval = this._global.setInterval;
    const prevSetTimeout = this._global.setTimeout;

    this.useRealTimers();

    let cbErr = null;
    let errThrown = false;
    try {
      cb();
    } catch (e) {
      errThrown = true;
      cbErr = e;
    }

    this._global.clearImmediate = prevClearImmediate;
    this._global.clearInterval = prevClearInterval;
    this._global.clearTimeout = prevClearTimeout;
    this._global.process.nextTick = prevNextTick;
    this._global.setImmediate = prevSetImmediate;
    this._global.setInterval = prevSetInterval;
    this._global.setTimeout = prevSetTimeout;

    if (errThrown) {
      throw cbErr;
    }
  }

  useRealTimers() {
    const global = this._global;
    setGlobal(global, 'clearImmediate', this._timerAPIs.clearImmediate);
    setGlobal(global, 'clearInterval', this._timerAPIs.clearInterval);
    setGlobal(global, 'clearTimeout', this._timerAPIs.clearTimeout);
    setGlobal(global, 'setImmediate', this._timerAPIs.setImmediate);
    setGlobal(global, 'setInterval', this._timerAPIs.setInterval);
    setGlobal(global, 'setTimeout', this._timerAPIs.setTimeout);

    global.process.nextTick = this._timerAPIs.nextTick;
  }

  useFakeTimers() {
    this._createMocks();

    const global = this._global;
    setGlobal(global, 'clearImmediate', this._fakeTimerAPIs.clearImmediate);
    setGlobal(global, 'clearInterval', this._fakeTimerAPIs.clearInterval);
    setGlobal(global, 'clearTimeout', this._fakeTimerAPIs.clearTimeout);
    setGlobal(global, 'setImmediate', this._fakeTimerAPIs.setImmediate);
    setGlobal(global, 'setInterval', this._fakeTimerAPIs.setInterval);
    setGlobal(global, 'setTimeout', this._fakeTimerAPIs.setTimeout);

    global.process.nextTick = this._fakeTimerAPIs.nextTick;
  }

  getTimerCount() {
    this._checkFakeTimers();

    return this._timers.size + this._immediates.length + this._ticks.length;
  }

  private _checkFakeTimers() {
    if (this._global.setTimeout !== this._fakeTimerAPIs.setTimeout) {
      this._global.console.warn(
        `A function to advance timers was called but the timers API is not ` +
          `mocked with fake timers. Call \`jest.useFakeTimers()\` in this ` +
          `test or enable fake timers globally by setting ` +
          `\`"timers": "fake"\` in ` +
          `the configuration file. This warning is likely a result of a ` +
          `default configuration change in Jest 15.\n\n` +
          `Release Blog Post: https://jestjs.io/blog/2016/09/01/jest-15.html\n` +
          `Stack Trace:\n` +
          formatStackTrace(new Error().stack!, this._config, {
            noStackTrace: false,
          }),
      );
    }
  }

  private _createMocks() {
    const fn = (impl: Function) =>
      // @ts-ignore TODO: figure out better typings here
      this._moduleMocker.fn().mockImplementation(impl);

    // TODO: add better typings; these are mocks, but typed as regular timers
    this._fakeTimerAPIs = {
      clearImmediate: fn(this._fakeClearImmediate.bind(this)),
      clearInterval: fn(this._fakeClearTimer.bind(this)),
      clearTimeout: fn(this._fakeClearTimer.bind(this)),
      nextTick: fn(this._fakeNextTick.bind(this)),
      setImmediate: fn(this._fakeSetImmediate.bind(this)),
      setInterval: fn(this._fakeSetInterval.bind(this)),
      setTimeout: fn(this._fakeSetTimeout.bind(this)),
    };
  }

  private _fakeClearTimer(timerRef: TimerRef) {
    const uuid = this._timerConfig.refToId(timerRef);

    if (uuid) {
      this._timers.delete(String(uuid));
    }
  }

  private _fakeClearImmediate(uuid: TimerID) {
    this._immediates = this._immediates.filter(
      immediate => immediate.uuid !== uuid,
    );
  }

  private _fakeNextTick(callback: Callback, ...args: Array<any>) {
    if (this._disposed) {
      return;
    }

    const uuid = String(this._uuidCounter++);

    this._ticks.push({
      callback: () => callback.apply(null, args),
      uuid,
    });

    const cancelledTicks = this._cancelledTicks;
    this._timerAPIs.nextTick(() => {
      if (!cancelledTicks.hasOwnProperty(uuid)) {
        // Callback may throw, so update the map prior calling.
        cancelledTicks[uuid] = true;
        callback.apply(null, args);
      }
    });
  }

  private _fakeSetImmediate(callback: Callback, ...args: Array<any>) {
    if (this._disposed) {
      return null;
    }

    const uuid = String(this._uuidCounter++);

    this._immediates.push({
      callback: () => callback.apply(null, args),
      uuid,
    });

    const immediates = this._immediates;
    this._timerAPIs.setImmediate(() => {
      this._fakeClearImmediate(uuid);
      immediates.find(x => x.uuid === uuid) && callback.apply(null, args);
    });

    return uuid;
  }

  private _fakeSetInterval(
    callback: Callback,
    intervalDelay?: number,
    ...args: Array<any>
  ) {
    if (this._disposed) {
      return null;
    }

    if (intervalDelay == null) {
      intervalDelay = 0;
    }

    const uuid = this._uuidCounter++;

    this._timers.set(String(uuid), {
      callback: () => callback.apply(null, args),
      expiry: this._now + intervalDelay,
      interval: intervalDelay,
      type: 'interval',
    });

    return this._timerConfig.idToRef(uuid);
  }

  private _fakeSetTimeout(
    callback: Callback,
    delay?: number,
    ...args: Array<any>
  ) {
    if (this._disposed) {
      return null;
    }

    // eslint-disable-next-line no-bitwise
    delay = Number(delay) | 0;

    const uuid = this._uuidCounter++;

    this._timers.set(String(uuid), {
      callback: () => callback.apply(null, args),
      expiry: this._now + delay,
      interval: undefined,
      type: 'timeout',
    });

    return this._timerConfig.idToRef(uuid);
  }

  private _getNextTimerHandle() {
    let nextTimerHandle = null;
    let soonestTime = MS_IN_A_YEAR;

    this._timers.forEach((timer, uuid) => {
      if (timer.expiry < soonestTime) {
        soonestTime = timer.expiry;
        nextTimerHandle = uuid;
      }
    });

    return nextTimerHandle;
  }

  private _runTimerHandle(timerHandle: TimerID) {
    const timer = this._timers.get(timerHandle);

    if (!timer) {
      return;
    }

    switch (timer.type) {
      case 'timeout':
        const callback = timer.callback;
        this._timers.delete(timerHandle);
        callback();
        break;

      case 'interval':
        timer.expiry = this._now + (timer.interval || 0);
        timer.callback();
        break;

      default:
        throw new Error('Unexpected timer type: ' + timer.type);
    }
  }
}