Model.findOneAndUpdate() has infinite loop when there's Map in the dbref's schema

[andyzhau]

Do you want to request a feature or report a bug?
It's a bug.

What is the current behavior?
Model.findOneAndUpdate() hangs when update has a reference model which has a Map as a field.

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

const User = mongoose.model('User', {
      maps: { type: Map, of: String },
});

const Post = mongoose.model('Post', {
      user: { type: Schema.Types.ObjectId, ref: 'User' },
});

const user = await User.create({});
await Post.findOneAndUpdate({user}, {user}, {upsert: true, new: true}); /// hangs here.

I took a quick investigation. In lib/helpers/common.js function modifiedPaths will recursive call itself when there's map, because there is a key $__parent generated when model has a Map.

function modifiedPaths(update, path, result) {
  var keys = Object.keys(update || {});
  var numKeys = keys.length;
  result = result || {};
  path = path ? path + '.' : '';

  for (var i = 0; i < numKeys; ++i) {
    var key = keys[i];
    var val = update[key];

    if (key.startsWith('$')) continue;   // << Works if I added this line

    result[path + key] = true;
    if (utils.isMongooseObject(val) && !Buffer.isBuffer(val)) {
      val = val.toObject({ transform: false, virtuals: false });
    }
    if (shouldFlatten(val)) {
      modifiedPaths(val, path + key, result);
    }
  }

  return result;
}

What is the expected behavior?
No infinite loop.

Please mention your node.js, mongoose and MongoDB version.
node v10.5.0
mongoose 5.2.4
mongodb v3.6.4

[vkarpov15]

Below script executes without error on mongoose 5.2.4, can you modify the below script to repro your issue?

const assert = require('assert');
const mongoose = require('mongoose');
mongoose.set('debug', true);

const GITHUB_ISSUE = `gh6750`;
const connectionString = `mongodb://localhost:27017/${ GITHUB_ISSUE }`;
const { Schema } = mongoose;

run().then(() => console.log('done')).catch(error => console.error(error.stack));

async function run() {
  await mongoose.connect(connectionString);
  await mongoose.connection.dropDatabase();

  const User = mongoose.model('User', {
      maps: { type: Map, of: String },
});

  const Post = mongoose.model('Post', {
    user: { type: Schema.Types.ObjectId, ref: 'User' },
  });

  const user = await User.create({});
  const doc = await Post.findOneAndUpdate({user}, {user}, {upsert: true, new: true});
  console.log('Doc', doc);
}

[andyzhau]

Construct the map with a default '{}', then it can trigger error like

RangeError: Maximum call stack size exceeded

const assert = require('assert');
const mongoose = require('mongoose');
mongoose.set('debug', true);

const GITHUB_ISSUE = `gh6750`;
const connectionString = `mongodb://localhost:27017/${ GITHUB_ISSUE }`;
const { Schema } = mongoose;

run().then(() => console.log('done')).catch(error => console.error(error.stack));

async function run() {
  await mongoose.connect(connectionString);
  await mongoose.connection.dropDatabase();

  const User = mongoose.model('User', {
      maps: { type: Map, of: String, default: {} },
});

  const Post = mongoose.model('Post', {
    user: { type: Schema.Types.ObjectId, ref: 'User' },
  });

  const user = await User.create({});
  const doc = await Post.findOneAndUpdate({user}, {user}, {upsert: true, new: true});
  console.log('Doc', doc);
}

[vkarpov15]

Thanks for reporting, will fix asap