jasmine/src/core/StackClearer.js

getJasmineRequireObj().StackClearer = function(j$) {
  'use strict';

  const maxInlineCallCount = 10;
  // 25ms gives a good balance of speed and UI responsiveness when running
  // jasmine-core's own tests in Safari 18. The exact value isn't critical.
  const safariYieldIntervalMs = 25;

  function browserQueueMicrotaskImpl(global) {
    const unclampedSetTimeout = getUnclampedSetTimeout(global);
    const { queueMicrotask } = global;
    let yieldStrategy = 'count';
    let currentCallCount = 0; // for count strategy
    let nextSetTimeoutTime; // for time strategy

    return {
      clearStack(fn) {
        currentCallCount++;
        let shouldSetTimeout;

        if (yieldStrategy === 'time') {
          const now = new Date().getTime();
          shouldSetTimeout = now >= nextSetTimeoutTime;
          if (shouldSetTimeout) {
            nextSetTimeoutTime = now + safariYieldIntervalMs;
          }
        } else {
          shouldSetTimeout = currentCallCount >= maxInlineCallCount;
          if (shouldSetTimeout) {
            currentCallCount = 0;
          }
        }

        if (shouldSetTimeout) {
          unclampedSetTimeout(fn);
        } else {
          queueMicrotask(fn);
        }
      },
      setSafariYieldStrategy(strategy) {
        yieldStrategy = strategy;

        if (yieldStrategy === 'time') {
          nextSetTimeoutTime = new Date().getTime() + safariYieldIntervalMs;
        }
      }
    };
  }

  function nodeQueueMicrotaskImpl(global) {
    const { queueMicrotask } = global;

    return {
      clearStack(fn) {
        queueMicrotask(fn);
      },
      setSafariYieldStrategy() {}
    };
  }

  function messageChannelImpl(global) {
    const { setTimeout } = global;
    const postMessage = getPostMessage(global);

    let currentCallCount = 0;

    return {
      clearStack(fn) {
        currentCallCount++;

        if (currentCallCount < maxInlineCallCount) {
          postMessage(fn);
        } else {
          currentCallCount = 0;
          setTimeout(fn);
        }
      },
      setSafariYieldStrategy() {}
    };
  }

  function getUnclampedSetTimeout(global) {
    const { setTimeout } = global;
    if (!global.MessageChannel) {
      return setTimeout;
    }

    const postMessage = getPostMessage(global);
    return function unclampedSetTimeout(fn) {
      postMessage(function() {
        setTimeout(fn);
      });
    };
  }

  function getPostMessage(global) {
    const { MessageChannel, setTimeout } = global;
    const channel = new MessageChannel();
    let head = {};
    let tail = head;

    let taskRunning = false;
    channel.port1.onmessage = function() {
      head = head.next;
      const task = head.task;
      delete head.task;

      if (taskRunning) {
        setTimeout(task, 0);
      } else {
        try {
          taskRunning = true;
          task();
        } finally {
          taskRunning = false;
        }
      }
    };

    return function postMessage(fn) {
      tail = tail.next = { task: fn };
      channel.port2.postMessage(0);
    };
  }

  function getStackClearer(global) {
    const NODE_JS =
      global.process &&
      global.process.versions &&
      typeof global.process.versions.node === 'string';

    // Windows builds of WebKit have a fairly generic user agent string when no application name is provided:
    // e.g. "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/605.1.15 (KHTML, like Gecko)"
    const SAFARI_OR_WIN_WEBKIT =
      global.navigator &&
      /(^((?!chrome|android).)*safari)|(Win64; x64\) AppleWebKit\/[0-9.]+ \(KHTML, like Gecko\)$)/i.test(
        global.navigator.userAgent
      );

    if (NODE_JS) {
      // Unlike browsers, Node doesn't require us to do a periodic setTimeout
      // so we avoid the overhead.
      return nodeQueueMicrotaskImpl(global);
    } else if (SAFARI_OR_WIN_WEBKIT) {
      // queueMicrotask is dramatically faster than MessageChannel in Safari
      // and other WebKit-based browsers, such as the one distributed by Playwright
      // to test Safari-like behavior on Windows.
      return browserQueueMicrotaskImpl(global);
    } else {
      // MessageChannel is faster than queueMicrotask in supported browsers
      // other than Safari.
      return messageChannelImpl(global);
    }
  }

  return getStackClearer;
};