Deduced type of an array in a schema is plain array instead of mongoose array.

[DavidTelenko]

Prerequisites

• I have written a descriptive issue title

Mongoose version

8.6.2

Node.js version

20.18.0

MongoDB version

7.0.14

Operating system

Windows

Operating system version (i.e. 20.04, 11.3, 10)

10.0.22631

Issue

Here is simple example of schema in mongoose:

const ExampleSchema = new Schema(
  {
    names: [
      {
        type: String,
      },
    ],
  },
  {
    methods: {
      addToNames: async function (name: string) {
        // this.updateOne() // accessible
        this.names.addToSet(name); // Property 'addToSet' does not exist on type 'string[]'. [2339]
      },
    },
  },
);

this object in a methods is a hydrated document, however array deduced not as mongoose array but as plain array instead. Example demonstrates this issue by trying to use addToSet method of a mongoose array, but getting type error.

Same issue can be depicted with this example:

type IExampleDocument = HydratedDocumentFromSchema<typeof ExampleSchema>;
const Example = model<IExampleDocument>("example", ExampleSchema);
const example = await Example.create({ names: ["hello"] });
example.names.addToSet("example"); // Property 'addToSet' does not exist on type 'string[]'. [2339]

I have pretty vague understanding of how schemas in typescript should be properly defined, I've read that we can provide interfaces ourselves by using template parameters of model and Schema however it essentially produces a duplication in a boilerplate types and defies already defined principles of deduction established with HydratedDocumentFromSchema, InferSchemaType and other typescript helper functions.

[github-actions]

This issue is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 5 days

[vkarpov15]

It looks like this issue isn't limited to methods, you also get the same error with:

const TestModel = model('Test', ExampleSchema);

const doc = new TestModel({});
doc.names.addToSet('taco');

I'm investigating whether we can fix this without a breaking change.

[vkarpov15]

Unfortunately there isn't much we can do about this without breaking changes. However, we will make this change for Mongoose 9.