fix: GroupingGetterFunction should be allowed to return arbitrary value

[jesenko]

Underlying slickgrid logic only takes into account equality between values returned for grouping individial rows. Getter thus does not need to return string but might return arbitrary value (e.g. string, number, Date).

Typing return value as unknown will force underlying logic using grouping getter to take into consideration that user might specify grouping function that returns arbitrary value type for individual row. With previous getter signature, user was forced to specify function that returned string, which is however not currenly needed by internal slickgrid logic.

[ghiscoding]

I again disagree with this change, the GroupingGetterFunction is meant to be used by the getter property to get the column name which should always be a string. If I am wrong in my assumption then prove me wrong or else I will refuse this PR

[jesenko]

We are currently trying to port our quite extensive usage of the original, slightly modified SlickGrid to this fork and this surfaced when typechecking our codebase.

I guess that getter might contain

a) field of the row which is used for grouping (e.g. getter: "some_field" will result in row["some_field"] being used for grouping), OR
b) function, that takes row as argument and returns value to be used for grouping (not column / field name). E.g. getter: (row) => row["some_field"] || row["other_field"]. Note that return type of the function will be of whatever row["some_field"] or row["other_field"] contains, not string.

I belive relevant logic is here: https://github.com/6pac/SlickGrid/blob/508aa7b872408c9371f77267921bb053d1f7e290/src/slick.dataview.ts#L905C6-L905C6

[ghiscoding]

both a & b are already covered by the interface

type GroupingGetterFunction<T = any> = (value: T) => string;

interface Grouping<T = any> {
   // 
   getter?: string | GroupingGetterFunction<T>; can be a string or a function returning a string
}

so again, the interface seems correct as it is

[ghiscoding]

ahh actually I see what you mean, when it's a function it returns the item value directly. in that case I think any is better since that is what is used for the value type as shown below (unless you also change the value type to unknown)

SlickGrid/src/slick.dataview.ts

Lines 881 to 883 in 508aa7b

	protected extractGroups(rows: any[], parentGroup?: SlickGroup_) {
	let group: SlickGroup_;
	let val: any;

[jesenko]

Agreed - will change return type of function to any, probably can be refactored latter to also more fully typecheck underlying logic. Thank you!

[ghiscoding]

now thinking about it and I think it should actually be returning type T when the Generic Type is provided for the item datacontext type (which defaults to any when not provided), it is for the value so that should be the correct type to use. Sorry for asking to change it so many time, I just realized it now 😅

[ghiscoding]

damn I think I'm wrong again and this is the value not the datacontext, so it could really be anything

[ghiscoding]

This is now available in the latest release v5.7.0, thanks again for your contributions

[jesenko]

Thank you - for merging this and also for maintaining this great lib and making it future-proof!