MongoError: Updating the path '__v' would create a conflict at '__v'

[Polarisation]

Do you want to request a feature or report a bug?

Bug

What is the current behavior?

When using findByIdAndUpdate() or findOneAndUpdate() with the upsert option, a __v key, and $unset, the following error is thrown:

MongoError: Updating the path '__v' would create a conflict at '__v'
    at ~/mongoose-test/node_modules/mongodb-core/lib/connection/pool.js:581:63

This bug appears similar to #5973 which is supposed to have been fixed. As far as I can tell, the difference here is that in this case the $unset key is being used.

If the current behavior is a bug, please provide the steps to reproduce.

const mongoose = require('mongoose');
mongoose.Promise = global.Promise;

const GITHUB_ISSUE = `gh-7003`;
const connectionString = `mongodb://localhost:27017/${ GITHUB_ISSUE }`;

run().catch(error => console.error(error.stack));

async function run() {
  await mongoose.connect(connectionString);
  const schema = new mongoose.Schema({ name: String, description: String });
  const Model = mongoose.model('Model', schema);
  const doc = await Model.create({ name: 'test', description: 'we want to unset this description later' });
  await Model.findByIdAndUpdate(doc._id, {
    '$unset': { description: '' },
    __v: 0,
    name: 'update'
  }, { upsert: true });
  console.log('updated __v');
}

When running this script, an error is thrown before the console.log.

What is the expected behavior?

The record should update without at error. Remove either __v, $unset, or the upsert option from the example and it works as expected.

Please mention your node.js, mongoose and MongoDB version.

Node.js: v10.9.0
Mongoose: v5.2.14
MongoDB: v3.6.3 (with setFeatureCompatibilityVersion: 3.6)

[lineus]

@Polarisation if you change your findByIdAndUpdate update doc to:

  await Model.findByIdAndUpdate(doc._id, {
    '$unset': { description: '' },
    '$set': {
      __v: 0,
      name: 'blargh'
    }
  }, { upsert: true });

It will work as expected.

@vkarpov15 I marked this as a confirmed bug, but now I'm not so sure. If an update doc is passed in with one dollarKey, should all top level keys be dollarKeys? Marking as bug? for now.

after giving this some more thought, either way, I think this is a bug. It's obviously a bug if we should accept a mix of top level dollar/non-dollar keys, and it's a bug if not, because we should probably be returning an Error if we don't accept the combination of top level dollar/non-dollar keys.

[vkarpov15]

Thanks for reporting, will investigate ASAP