Typings: New Aggregation Type Issues [DateExpressionOperatorReturningNumber, AddToSet, ...]

[MichaelFedora]

Prerequisites

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

Running:

• Mongoose 6.4.1
• Typescript 4.7.4
• Node 14.19.1

Issue

This new update has messed up a log of my aggregation typings (like others).

1. Add DateExpressionOperatorReturningNumber to NumberExpression

This doesn't work currently, but it should. I believe it was forgotten:

const a: Expression = { $subtract: [
  { $dayOfWeek: new Date() } as Expression.DayOfWeek, // errors
  2
] };

2. Some stages and operators specify "Expressions" when they can take values as well

This breaks quite a few things ($addToSet as well):

const a: Expression.Reduce = {
  $reduce: {
    input: '$values',
    initialValue: { depth: -1 }, // errors
    in: {
      depth: '$$this.depth' // errors
    }
  }
};

const b: Expression.Reduce = {
  $reduce: {
    input: '$values',
    initialValue: 0, // errors
    in: { $add: ['$$value', '$$this'] }
  }
};

const c: PipelineStage.Set = {
  $set: {
    child: {
      foo: 'bar' // errors
    },
    friend: new ObjectId() // errors
  }
};

const a: Expression.ToInt = { $toInt: 2.5 }; // errors

3. AddToSet requires ArrayExpression

According to the docs it just takes an "expression" ( https://www.mongodb.com/docs/manual/reference/operator/aggregation/addToSet/ ).

4. Cond doesn't allow nested Conds

...because it is too strict on the first requirement being a BooleanExpression. I think switching most operators to accept a ConditionalExpressionOperator (with a <T> or otherwise) would help a lot, because IfNull is also throwing things.

---

Otherwise, reintroducing the old Pipeline type and/or having a more flexible Pipeline type in parallel, if we wanted/needed less strict checks would be great.

[Davies-Owen]

I'm experiencing this as well. Another example: $add and $subtract don't allow nested Conds:

const d: Expression.Add = {
  $add: [
    '$value',
    {
      $cond: { // errors
        if: {
          $lte: ["$value", "$otherValue"],
        },
        then: 12,
        else: 0,
      },
    },
  ],
};

[skrtheboss]

Avg requires ArrayExpression
According to the docs it just takes an "expression" or array of "expression" https://www.mongodb.com/docs/manual/reference/operator/aggregation/avg/#syntax

const d: Expression.Avg = { $avg: { $subtract: [{ $ifNull: ['$end', new Date()] }, '$start'] } }; // errors

[billouboq]

One of the type that does not work well is $ifNull inside other expression, had issues with it :

error TS2322: Type '{ $add: { $ifNull: (string | number)[]; }[]; }' is not assignable to type 'number | Expression | Expression[]'.
  Types of property '$add' are incompatible.
    Type '{ $ifNull: (string | number)[]; }[]' is not assignable to type '(string | number | NativeDate | ArrayElemAt | First | Last | Reduce | ObjectToArray | SetDifference | ... 78 more ... | Convert<...>)[]'.
      Type '{ $ifNull: (string | number)[]; }' is not assignable to type 'string | number | NativeDate | ArrayElemAt | First | Last | Reduce | ObjectToArray | SetDifference | ... 78 more ... | Convert<...>'.
        Object literal may only specify known properties, and '$ifNull' does not exist in type 'NativeDate | ArrayElemAt | First | Last | Reduce | ObjectToArray | SetDifference | SetIntersection | ... 77 more ... | Convert<...>'.

385        { $ifNull: ['$metrics.shares', 0] },

[darwin403]

Facing the same issue $ifNull problem.

No overload matches this call.
  Overload 1 of 2, '(pipeline?: PipelineStage[] | undefined, options?: AggregateOptions | undefined, callback?: Callback<{ date: string; totalVisibility: number; avgPosition: number; }[]> | undefined): Aggregate<...>', gave the following error.
    Type '{ $ifNull: (string | number)[]; }' is not assignable to type 'ArrayExpression<any>'.
      Object literal may only specify known properties, and '$ifNull' does not exist in type 'any[] | ArrayElemAt | First | Last | Reduce | ConcatArrays | Filter | Map | ObjectToArray | Range | ... 12 more ... | Shift'.
  Overload 2 of 2, '(pipeline: PipelineStage[], callback?: Callback<{ date: string; totalVisibility: number; avgPosition: number; }[]> | undefined): Aggregate<{ date: string; totalVisibility: number; avgPosition: number; }[]>', gave the following error.
    Type '{ $ifNull: (string | number)[]; }' is not assignable to type 'ArrayExpression<any>'.
      Object literal may only specify known properties, and '$ifNull' does not exist in type 'any[] | ArrayElemAt | First | Last | Reduce | ConcatArrays | Filter | Map | ObjectToArray | Range | ... 12 more ... | Shift'.

75             avgPosition: { $avg: { $ifNull: ["$position", 100] } },