Function checkIfCollectableByCounting

test/common/gc.js:149–180

* This requires --expose-internals. * This function can be used to check if an object factory leaks or not by * iterating over the heap and count objects with the specified class * (which is checked by looking up the prototype chain). * @param {(i: number) => number} fn The factory receiving ite

(fn, ctor, count, waitTime = 20)

 * @param {number} waitTime Optional breathing time for GC.
 */
async function checkIfCollectableByCounting(fn, ctor, count, waitTime = 20) {
  const { queryObjects } = require('v8');
  const { name } = ctor;
  const initialCount = queryObjects(ctor, { format: 'count' });
  console.log(`Initial count of ${name}: ${initialCount}`);
  let totalCreated = 0;
  for (let i = 0; i < count; ++i) {
    const created = await fn(i);
    totalCreated += created;
    console.log(`#${i}: created ${created} ${name}, total ${totalCreated}`);
    await wait(waitTime);  // give GC some breathing room.
    const currentCount = queryObjects(ctor, { format: 'count' });
    const collected = totalCreated - (currentCount - initialCount);
    console.log(`#${i}: counted ${currentCount} ${name}, collected ${collected}`);
    if (collected > 0) {
      console.log(`Detected ${collected} collected ${name}, finish early`);
      return;
    }
  }

  await wait(waitTime);  // give GC some breathing room.
  const currentCount = queryObjects(ctor, { format: 'count' });
  const collected = totalCreated - (currentCount - initialCount);
  console.log(`Last count: counted ${currentCount} ${name}, collected ${collected}`);
  // Some objects with the prototype can be collected.
  if (collected > 0) {
    console.log(`Detected ${collected} collected ${name}`);
    return;
  }

  throw new Error(`${name} cannot be collected`);
}

module.exports = {
  checkIfCollectable,