insertMany does not respect discriminator when using optional key

[thernstig]

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

What is the current behavior?
When using a discriminator child model with the third argument (the optional key), it is then not possible to do a parent.insertMany with discriminator value set to the same as the optional key. It will instead create the document against the parent schema only, dropping the other properties.

If the current behavior is a bug, please provide the steps to reproduce.
Consider that kind is a discriminator key. The kind will not be respected when having set 'child' as the optional key.

await Test.insertMany([
    {
        title: 'Title 1',
        __t: 'child',
        label: 'label 1'
    }
]);

const TestChild= Test.discriminator(
  'TestChild',
  testChildSchema,
  'child'
);

What is the expected behavior?
For the child schema properties/values to be inserted into the created document(s)

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
Moongose 5.5.2
Mongodb 3.6.3
Node.js 10.13.0

[thernstig]

Actually it does not seem to work for a normal const parent = new Parent() followed by parent.save() either.

[thernstig]

Oh and most likely a separate issue, but https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/mongoose/index.d.ts does not account for the third parameter to discriminator()

[vkarpov15]

Thanks for reporting, will investigate.

We do not support @types/mongoose, so you'll have to open up an issue on DefinitelyTyped for that.