v8/test/mjsunit/async-hooks/async-await-tree.js

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// Flags: --expose-async-hooks --harmony-await-optimization

// Check for async/await asyncIds relation
(function() {
  let asyncIds = [], triggerIds = [];
  let ah = async_hooks.createHook({
    init(asyncId, type, triggerAsyncId, resource) {
      if (type !== 'PROMISE') {
        return;
      }
      asyncIds.push(asyncId);
      triggerIds.push(triggerAsyncId);
    },
  });
  ah.enable();

  // Simplified version of Node.js util.promisify(setTimeout),
  // but d8 ignores the timeout of setTimeout.
  function sleep0() {
    const promise = new Promise(function(resolve, reject) {
      try {
        setTimeout((err, ...values) => {
          if (err) {
            reject(err);
          } else {
            resolve(values[0]);
          }
        }, 0);
      } catch (err) {
        reject(err);
      }
    });
    return promise;
  }

  async function foo() {
    await sleep0();
  }

  assertPromiseResult(
    foo().then(function() {
      assertEquals(triggerIds[2], asyncIds[1]);
      assertEquals(triggerIds[3], asyncIds[0]);
      assertEquals(triggerIds[4], asyncIds[3]);
      assertEquals(triggerIds[6], asyncIds[5]);
    }));
})();