[@types/mongoose] MongooseUpdateQuery.push? is undefined

[notaphplover]

• I tried using the @types/mongoose v5.10.0 package and had problems.
• I tried using the latest stable version of tsc. https://www.npmjs.com/package/typescript
• Mention the Authors: @horiuchi @lukasz-zak @jendrikw @ethanresnick @vologab

Given any type T extends Document, Pick<MongooseUpdateQuery<Document>, '$push'> is equal to { $push?: undefined; }.

I expect to be able to use MongooseUpdateQuery to push elements in a subdocument.

Minimal example:

import { Document, MongooseUpdateQuery } from 'mongoose';

interface Foo extends Document {
  nonArrayProperty: number;
  bar: number[];
}

const query: MongooseUpdateQuery<Foo> = {
  $push: {
    bar: 2,
  },
};

Playground Link

On the other hand, no errors are thrown applying the same process to a type T which does not extends the Document class:

import { MongooseUpdateQuery } from 'mongoose';

interface Foo {
  nonArrayProperty: number;
  bar: number[];
}

const query: MongooseUpdateQuery<Foo> = {
  $push: {
    bar: 2,
  },
};

Playground Link

Is this the expected behavior?

Additional information

It seems there is a conflict at mongodb PushOperator type when TSchema extends Document. PushOperator<Document> is equal to never.

If we explore the mongodb PushOperator type:

export type PushOperator<TSchema> = ({
    readonly [key in KeysOfAType<TSchema, ReadonlyArray<any>>]?:
        | UpdateOptionalId<Unpacked<TSchema[key]>>
        | ArrayOperator<Array<UpdateOptionalId<Unpacked<TSchema[key]>>>>;
} &
    NotAcceptedFields<TSchema, ReadonlyArray<any>>) & {
    readonly [key: string]: ArrayOperator<any> | any;
};

We can see two intersections of types. If we try:

type SimplifiedPushOperator<TSchema> = ({
    readonly [key in KeysOfAType<TSchema, ReadonlyArray<any>>]?:
        | UpdateOptionalId<Unpacked<TSchema[key]>>
        | ArrayOperator<Array<UpdateOptionalId<Unpacked<TSchema[key]>>>>;
} &
    NotAcceptedFields<TSchema, ReadonlyArray<any>>);

type DocumentSimplifiedPushOperator = SimplifiedPushOperator<Document>

The type DocumentSimplifiedPushOperator is equal to never, so we can asume there must be a conflict in that type intersection.

Additional information 2

Looking at your types:

 export type MongooseUpdateQuery<S> = mongodb.UpdateQuery<S> & mongodb.MatchKeysAndValues<S>;

The following change would probably solve the issue:

- export type MongooseUpdateQuery<S> = mongodb.UpdateQuery<S> & mongodb.MatchKeysAndValues<S>;
+ export type MongooseUpdateQuery<S> = mongodb.UpdateQuery<DocumentDefinition<S>> & mongodb.MatchKeysAndValues<DocumentDefinition<S>>;

But there's probably a good reason to not to do that change.

Additional information 3

It seems you have UpdateQuery which is

export type UpdateQuery<D> = MongooseUpdateQuery<DocumentDefinition<D>>;

It feels a bit confusing, it's not easy to figure out when I should use MongooseUpdateQuery over UpdateQuery.

[orta]

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