How to type `QueryWithHelpers` so that it returns both `HydratedDocument` and `FlattenMaps`?

[nikzanda]

Prerequisites

• I have written a descriptive issue title

Mongoose version

8.12.1

Node.js version

20.10.0

MongoDB version

6.0.2

Operating system

macOS

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

No response

Issue

In the example provided in the documentation, the query helper byName returns a HydratedDocument of Project. However, if the query is lean, it should consequently return the FlattenMaps type. How can the typing be corrected?"

Reproduction link here.

[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

[nikzanda]

Still active

[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

[nikzanda]

Hi @vkarpov15, is there any news in this issue? Thanks

[vkarpov15]

Here's how you can fix. First, you need to add IProject as the raw doc type for your ProjectQueryHelpers as follows:

interface ProjectQueryHelpers {
  byName(
    name: string
  ): QueryWithHelpers<
    HydratedDocument<IProject, IProjectVirtuals>[],
    HydratedDocument<IProject, IProjectVirtuals>,
    ProjectQueryHelpers,
    IProject // <-- add this
  >;
}

Second, put byName() before lean() as follows:

  const result = await ProjectModel.find()
    .where('stars')
    .gt(1000)
    .byName('mongoose') 
    .lean();

Putting lean() last makes it easier for byName to not have to handle lean results.

As a side note, we should do some work to make it so that the following is typed properly. Right now TypeScript types assume the result of the following query is not lean.

  const result = await ProjectModel.find()
    .where('stars')
    .gt(1000)
    .lean()
    .find();

[nikzanda]

Thanks, Valeri, I followed your instructions and now it works!

In addition to the last example you wrote, the typing is also incorrect in the following script: instead of typing Map<string, FlattenMaps<...>>, type directly FlattenMaps<...> because lean() is called after transform() (by swapping transform and lean, everything works correctly).

const result = await ProjectModel
  .find()
  .transform((docs) => new Map(docs.map((doc) => [doc._id.toString(), doc])))
  .lean();

At this point, can we close the issue? Or would you prefer to keep it open as a reminder to improve these typings?

[vkarpov15]

I'll keep this open as a reminder to take a look and see if we can improve the handling of transform() and lean().