ValidationError when using array in Schema

[BrunoGodefroy]

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

What is the current behavior?
After defining my schema similar to the following one:

const UserSchema = new mongoose.Schema({
  roles: {
    type: [String],
    index: true,
  },
});

mongoose.model('User', UserSchema)

If I try to instantiate a new User like this:

const user = new User({ roles: ['super-admin'] });

It raises the following exception ValidationError: User validation failed: roles: Cast to Array failed for value "[ 'super-admin' ]" at path "roles"

Instantiating the user with an empty roles array does not raise any exception.
This is happening on mongoose@5.6.9, downgrading to 5.6.8 fixes it.

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

The schema shown above should be enough to reproduce the issue.

What is the expected behavior?
No ValidationError exception raised when instantiating a model with an array in the schema.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
node 10.16.0
mongoose 5.6.9
mongo 4.0.4

[vkarpov15]

The below script executes without any error for me, please modify the below script to demonstrate your issue.

const assert = require('assert');
const mongoose = require('mongoose');

const GITHUB_ISSUE = `gh8053`;
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, { useNewUrlParser: true });
  await mongoose.connection.dropDatabase();

  console.log(mongoose.version);

  const UserSchema = new mongoose.Schema({
    roles: {
      type: [String],
      index: true,
    },
  });

  const User = mongoose.model('User', UserSchema);

  const user = new User({ roles: ['super-admin'] });

  await user.save();
}

Output:

$ node gh-8053.js 
5.6.9
(node:25883) DeprecationWarning: collection.ensureIndex is deprecated. Use createIndexes instead.
done

[BrunoGodefroy]

@vkarpov15 I have put together a small reproduction repository: https://github.com/BrunoGodefroy/repro-mongoose-issue-8053

I tried to simplify it at a maximum to showcase the error, I could not remove jest while keeping the bug so it might be caused by babel transpiling the code for jest.

Hope that helps

[Green-Cat]

I also have this error when testing an application using mongoose schemas with arrays with jest.
Error does not occur in mongoose 5.6.7.

[xaviarnl]

I also have this error, and also with a string array. It appeared without any changes in that code for quite some time. The only difference was that I upgraded Mongoose to 5.6.9.
When I downgrade(d) to 5.6.8, the problem disappears again.

[vkarpov15]

This appears to be yet another bug with Jest. Not to harp about this too much, but Jest is horribly broken and you should really use Mocha or some other framework that doesn't invent its own JavaScript runtime that isn't quite Node.js or a browser. Because Jest makes up its own runtime by monkeypatching everything, code that works fine in Node.js may not work in Jest and vice versa, so Jest is not a reliable way to test Node.js projects.

It looks like this issue comes down to Jest stubbing out require(), so if you require('./) in a directory where the parent dir happens to have a file with the same name as the current directory, Jest's require() gives you the parent dir's file. For example, suppose you have the below file structure:

- test.js
- dir.js
- dir
  - index.js
  - fn.js

test.js

const fn = require('./dir/fn');

it('test', function() {
  console.log(fn());
});

dir.js

module.exports = 'top-level';

dir/index.js

module.exports = 'nested';

dir/fn.js

module.exports = function() {
  return require('./');
};

Running test.js will output:

top-level

As opposed to nested like in Node.js.