feat(func): add `FuncWithIndex` and `FuncWithIndexNoReturn`

[quantumsheep]

Hey! I regularly write some functions that I pass to lo.Map and it's a hassle to have to pass the index every time.

Currently:

lo.Map(slice, func (v string, _ int) string {
	return doThing(v)
})

With the PR:

lo.Map(slice, lo.FuncWithIndex(doThing))

I'm not sure about the naming, it could simply be WithIndex.

I hope you like the idea.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.35%. Comparing base (efef0ff) to head (7b493bc).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #565      +/-   ##
==========================================
+ Coverage   94.33%   94.35%   +0.01%     
==========================================
  Files          17       17              
  Lines        2790     2798       +8     
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+ Hits         2632     2640       +8     
  Misses        154      154              
  Partials        4        4              

Flag	Coverage Δ
unittests	94.35% <100.00%> (+0.01%)	:arrow_up:

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[itroot]

Wow. also faced that issue, and made a quite similar solution:

• https://github.com/samber/lo/issues/330#issuecomment-2507770542

[quantumsheep]

Wow. also faced that issue, and made a quite similar solution:

* [Curried map, reduce and filter for partial application  #330 (comment)](https://github.com/samber/lo/issues/330#issuecomment-2507770542)

Glad to see I'm not the only one wanting a feature like this :)

[samber]

I agree.

But I would vote for duplicating lo.Map helper:

• lo.Map
• lo.MapI

[quantumsheep]

@samber lo.MapI would be the version with or without index?

If it's the one with index, I wonder if that's a good idea as it will break many projects. Or it will require a major update.

What do you think?

[samber]

Yes 😅

I would break a large ecosystem. We would need to group all that changes into a single v2 major update.

I'm just sharing some ideas. Not telling we are going to do it right now 😇

[quantumsheep]

Then I really prefer this option! I'm not sure how people use lo.Map right now but I guess the index argument is not that much used.

Is there a place where contributors can discuss the changes for v2? I would like to help 😄

[samber]

@quantumsheep see #579