fix(pkFactory): use pkFactory for operations with insert as side effect

[smeijer]

Description

As described in issue NODE-2275, the provided pkFactory is not being used for all _id generating methods. Or better said, all methods that can insert a document in some way.

It's being used for col.insertOne and col.insertMany, but not for findOneAndUpdate, bulk.insert or bulk.find.upsert.

This is my attempt to fix that.

Small reproduction to experience the issue yourself:

const Client = require('mongodb');
 
function CustomPKFactory() {}
CustomPKFactory.prototype = new Object();
CustomPKFactory.count = 0;
CustomPKFactory.createPk = function() {
return ++CustomPKFactory.count;
};
 
const host = 'mongodb://localhost:27017';
const options = { pkFactory: CustomPKFactory };
 
Client.connect(host, options, async (err, client) => {
  const db = client.db('pkFactory');
  const col = db.collection('test_custom_key');
  await col.deleteMany({});
 
  // ✓ expected _id: 1 | received _id: 1
  await col.insertOne({ a: 1 });
 
  // ⨉ expected _id: 2 | received _id: ObjectId(…)
  await col.findOneAndUpdate({ a: 2 }, { $set: { b: 2 } }, { upsert: true });
 
  const bulk = col.initializeUnorderedBulkOp();
 
  // ⨉ expected _id: 3 | received _id: ObjectId(…)
  bulk.insert({ a: 3 });
 
  // ⨉ expected _id: 4 | received _id: ObjectId(…)
  bulk
    .find({ a: 4 })
    .upsert()
    .update({ $set: { b: 4 } });
 
  await bulk.execute();
});

What changed?
Instead of simply using ObjectId to generate the id, the pkFactory is now being used.

Are there any files to ignore?
Not really, I only changed two files. Existing of 22 additions and 4 deletions. The change isn't that big.

---

fixes https://jira.mongodb.org/projects/NODE/issues/NODE-2275

[daprahamian]

We can probably add the pkFactory support for bulk inserts. However, I do not think that it is possible at this time to add client-side id creation for upserts:

1. As of MongoDB 4.2, updates can be pipelines
2. It would deviate from other drivers that do not have this behavior
3. This mutates a user-passed document in a way it previously didn't, which can lead to unexpected behavior

If you'd like to put up a PR for just the change to bulk inserts, we could review that separately.

[daprahamian]

Closing due to lack of response.