TypeScript QueryHelpers return any instead of model type

[florianwalther-private]

Prerequisites

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

Mongoose version

6.5.3

Node.js version

16.3.2

MongoDB server version

5.0.11

Description

I implemented a query helper function following the tutorial documentation in the documentation.

As soon as I add this method, the return value of that query turns into any. It should return the proper model type instead.

Steps to Reproduce

Implement a query helper as outlined in the documentation: https://mongoosejs.com/docs/typescript/query-helpers.html

Expected Behavior

The return type after calling the query helper function should be the appropriate model type.

[hasezoey]

i think the mentioned documentation is at least slightly out-of-date, because a proper type for query-helpers should be QueryWithHelpers instead of just Query?

[florianwalther-private]

I'm not sure what the correct return type is because I find it a bit confusing, but it should certainly not be any. After calling exec()/await, I want the model back like it does without the query helper chained to it.

[hasezoey]

re #12347 (comment)

but the referenced (my) issue is not about the documentation

from what i can tell, this issue is about the documentation because "you followed the documentation, but its not working" and after having taken a look at the documentation and the current code in mongoose's actual types, i came to the conclusion that the documentation is probably outdated

---

reason for the documentation being outdated:
since the documentation has been written QueryWithHelpers has been added, which should make the types easier & cleaner, see

mongoose/types/query.d.ts

Line 24 in 0af4cb8

type QueryWithHelpers<ResultType, DocType, THelpers = {}, RawDocType = DocType> = Query<ResultType, DocType, THelpers, RawDocType> & THelpers;

by taking care of the Query<...> & Type

also the documentation lists the first parameter as a static any to Query<any, ...>, which is the result type, and so ending up in the wrong type

TL;DR: change your type to QueryWithHelpers for less code, and also change the first parameter from any to the actual return type

---

currently the documentation is basically guiding to be like (like in issue #12347)

mongoose/types/models.d.ts

Line 405 in 6cb1284

): QueryWithHelpers<any, ResultDoc, TQueryHelpers, T>;

here it should actually be ResultDoc or {} and definitely not any, see

mongoose/types/query.d.ts

Line 172 in 0af4cb8

class Query<ResultType, DocType, THelpers = {}, RawDocType = DocType> implements SessionOperation {

mongoose/types/query.d.ts

Lines 182 to 184 in 0af4cb8

	/** Executes the query */
	exec(callback: Callback<ResultType>): void;
	exec(): Promise<ResultType>;

TL;DR: if you are following the documentation, then you will be guaranteed to get any as a result after doing query.exec() (or query.then or implicitly like await query)

[florianwalther-private]

@hasezoey

Thank you for the explanation. I didn't know that only the docs were wrong.

But I'm unsure what to pass instead of any. If I only pass the interface type I use for my model, it doesn't work. Instead, I copy pasted the return type I get from normal queries, which works, but is very long and ugly:

(mongoose.Document<unknown, any, User> & User & Required<{
    _id: mongoose.Types.ObjectId;
}>) | null

Can you give me any tips here?

Also, if I understand it correctly, QueryWithHelpers lets me remove the TQueryHelpers type argument. Is there any other difference? I noticed that my code works the same with and without this argument even if I use the normal Query type.

[hasezoey]

Also, if I understand it correctly, QueryWithHelpers lets me remove the TQueryHelpers type argument. Is there any other difference? I noticed that my code works the same with and without this argument even if I use the normal Query type.

i basically suggested this because mongoose uses that internally over just Query, but i dont see other differences

Instead, I copy pasted the return type I get from normal queries, which works, but is very long and ugly:

the expected return-type (if the query returns a single) should be a document (or document array), which should be done with HydratedDocument<YourInterfaceType>, also if you have this once you can re-use that argument for both the first and second generic

like (updated documentation):

// note the "T" generic is just to store the same result for both the first and second generic for "QueryWithHelpers"
type ProjectModelQuery<T = HydratedDocument<Project>> = QueryWithHelpers<T | null, T, ProjectQueryHelpers>;
// or
type ProjectModelQuery = QueryWithHelpers<HydratedDocument<Project> | null, HydratedDocument<Project>, ProjectQueryHelpers>;

[florianwalther-private]

@hasezoey Thank you so much! I think I tried HydratedDocument earlier but it didn't work because I didn't add the | null. Now it works!

[vkarpov15]

Fixed by #12507