_id field bug introduced with v5.4.11

[hanMarr]

On Friday, Feb 8th, we started experiencing a failure on our integration tests (that spin up a in memory version of mongodb, inserts docs, and runs tests). There were a series of failures but it started with this one:

The _id field cannot be changed from {_id: ObjectId('5c648eb8ec93cd5888f9c9de')} to {_id: "5c648eb8ec93cd5888f9c9de"}.

This error happened when we were trying to write to mongo with the ".replaceOne()" method.

After testing out many versions of mongodb and mongodb-memory-server, we finally nailed down the issue to the mongoose library. We were using mongoose 5.4.12.

To reproduce:
use mongodb v 3.1.13 and mongodb-memory-server v3.1.1 and mongoose v5.4.11 (this is the version where the problem started but it was carried through to 5.4.12). node v10.6.0

The solution to our issue was to revert back to mongoose 5.4.10 (using the same mongodb libraries as above) still using the same version of the other libraries listed above.

[rvillane]

we are experiencing a very similar issue, like if a recent change on Mongoose is messing up with the type of "_id" on existing documents. Seems that is trying to cast from ObjectId to String. As you pointed out 5.4.11 is the version where this behavior was introduced.

Any ideas ?

[ahce]

@vkarpov15 Please check this.

The bug is introduced in this commit

exampleBreak is broken because _id false from otherProps causes the _id deletion of the schema. It only happens when otherProps is used as an object.

const mongoose = require('mongoose');

const otherProps = {
  _id: false,
  prop: { type: String }
};

const exampleBreak = new mongoose.Schema(
  {
    name: {
      type: String
    },
    data: otherProps
  },
  {
    timestamps: true
  }
);

const exampleWorks = new mongoose.Schema(
  {
    name: {
      type: String
    },
    data: [otherProps]
  },
  {
    timestamps: true
  }
);

const ExampleBreak = mongoose.model('exampleBreak', exampleBreak);
const ExampleWorks = mongoose.model('exampleWorks', exampleWorks);

async function run() {
  console.log('run');
  const { connection } = await mongoose.connect('YOUR_URI', {
    dbName: 'YOUR_DB_NAME',
    useNewUrlParser: true
  });
  const objWorks = {
    name: 'test',
    data: [{ prop: 'prop' }]
  };
  const objBreak = {
    name: 'test',
    data: { prop: 'prop' }
  };

  await connection.dropDatabase();

  try {
    const doc = await ExampleWorks.create(objWorks);

    console.log(doc);
  } catch (err) {
    console.log(err);
  }

  try {
    const doc = await ExampleBreak.create(objBreak);

    console.log(doc);
  } catch (err) {
    console.log(err);
  }
}

run();

[cosminn777]

We also moved back to mongoose 5.4.10 (some find queries were not working after the update).
Mongodb 4.0.6

[vkarpov15]

@ahce we fixed this in master, but your schema doesn't do what you expect it'll do. Your schema:

const otherProps = {
  _id: false,
  prop: { type: String }
};

const exampleBreak = new mongoose.Schema(
  {
    name: {
      type: String
    },
    data: otherProps
  },
  {
    timestamps: true
  }
);

Does not remove a nested._id path. It instead creates a data._id path with arbitrary type. That data._id path would not be there if you didn't put _id: false. Please just remove that _id: false from your schema.