Unexpected error executing a lean query and passing the result of the query to a function that accepts a variable of that interface type.

[nikzanda]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.10.2

Node.js version

20.10.0

MongoDB server version

6.0.2

Typescript version (if applicable)

5.7.2

Description

I have a model Post that references the model User. The User model includes an embedded field, addresses, which is overridden by the type UserDocumentOverrides using Types.DocumentArray<AddressInstance>. For some reason, this override causes a typing error when performing a lean query on the Post model and passing the query result to a function that expects a parameter of type IPost[].

Steps to Reproduce

Reproduction link here.

P.S. If I locally comment out line 21 of the user.ts file, the error disappears. However, for some reason, on StackBlitz, the error remains.

Expected Behavior

As a workaround, I can manually infer the type during the query .lean<IPost[]>(). However, I don't expect this type of error and having to manually specify the typing.

[vkarpov15]

The following looks like it fixes the issue:

type UserDocumentOverrides = {
  addresses: Types.DocumentArray<IAddress>;
};

You just need to pass the raw document interface to Types.DocumentArray, not the hydrated document interface

[nikzanda]

The following looks like it fixes the issue:

type UserDocumentOverrides = {
addresses: Types.DocumentArray;
};
You just need to pass the raw document interface to Types.DocumentArray, not the hydrated document interface

I'm not sure if this is the correct solution. I tried to further complicate the code by adding virtual fields to address and a document override field:

This forces me to type address in Types.DocumentArray as IAddress & IAddressDocumentOverrides & IAddressVirtuals, otherwise a function that accepts AddressInstance as a parameter returns an error if I pass user.addresses. This, in my opinion, is not very elegant to look at or to write:

Additionally, the same error for which I opened this issue remains:

[vkarpov15]

In that case, try the following. Does this work for you?

import {
  HydratedArraySubdocument,
} from 'mongoose';
import addressSchema, {
  IAddress,
  IAddressDocumentOverrides,
  IAddressVirtuals,
} from './embedded/address';

type UserDocumentOverrides = {
  addresses: Types.DocumentArray<
    HydratedArraySubdocument<
      IAddress,
      IAddressDocumentOverrides & IAddressVirtuals
    >
  >;
};

[nikzanda]

Sorry, but the solution you provided to me is not working. I have updated the repository, and you can see that the described error remains the same. Furthermore, your solution is very similar to the initial code I wrote: I typed addresses as Types.DocumentArray<AddressInstance>, where AddressInstance is a HydratedSingleSubdocument, whereas you used HydratedArraySubdocument.

[vkarpov15]

Looking into it further, this looks like expected behavior. postsFn() takes in an array of IPost, and IPost means user may be a UserInstance. But the result from .find().lean() will include a lean user doc, not a fully hydrated user doc. The error that appears, Type 'FlattenMaps<IMobilePhone>[]' is missing the following properties from type 'DocumentArray<IMobilePhone, Subdocument<ObjectId, any, IMobilePhone> & IMobilePhone>': isMongooseDocumentArray, create, id, $pop, and 8 more., isn't great, but that's because Mongoose doesn't attempt to convert hydrated documents in the raw type into their lean equivalents. The recommended workaround is to make postsFn() take in the correct type, or don't pass in lean() query results to postsFn().