feat(collections/unstable): add index arg to methods

[canac]

Adds an index arg to collections' predicate/selector/transformer/discriminator method. I added it only to collection helpers that operate on iterables because collection helpers that operate on records don't seem as likely to need access to the key index. Please let me know if I missed any.

Closes #6288

[codecov]

Codecov Report

❌ Patch coverage is 66.08187% with 116 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.07%. Comparing base (6b93b78) to head (d2d5bb9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
collections/unstable_min_of.ts	30.55%	25 Missing ⚠️
collections/unstable_max_of.ts	36.11%	22 Missing and 1 partial ⚠️
collections/unstable_max_by.ts	50.00%	18 Missing ⚠️
collections/unstable_min_by.ts	50.00%	18 Missing ⚠️
collections/unstable_drop_while.ts	33.33%	14 Missing ⚠️
collections/unstable_take_last_while.ts	47.61%	11 Missing ⚠️
collections/unstable_sort_by.ts	85.18%	3 Missing and 1 partial ⚠️
collections/unstable_first_not_nullish_of.ts	83.33%	2 Missing ⚠️
collections/unstable_drop_last_while.ts	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6382      +/-   ##
==========================================
- Coverage   94.28%   94.07%   -0.22%     
==========================================
  Files         584      600      +16     
  Lines       43186    43528     +342     
  Branches     6933     6986      +53     
==========================================
+ Hits        40720    40947     +227     
- Misses       2413     2526     +113     
- Partials       53       55       +2     

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[kt3k]

I'm generally in favor of the idea. It looks useful in several places, and also this is aligned to the design of builtin map methods (such as map, filter, forEach, etc)

What do people think?

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Note: Currently we have policy of accepting any new feature in unstable_ prefixed path. That requires all these APIs duplicated in unstable_foo.ts, but that feels too unwieldy in this case. I'll discuss with core team about how to handle this particular case.

[timreichen]

What do people think?

I like it.

[iuioiua]

I'm in favour.

[iuioiua]

@kt3k should we add this in?

[canac]

I'm more than happy to rebase this if we want to move forward with it. Just let me know!

[iuioiua]

I suggest rebasing anyway 🙂

[iuioiua]

@kt3k, it seems like this is a good idea to add.

[tomas-zijdemans]

I support adding this!

[kt3k]

Hey, sorry for the very long delay in response!

This looks good to me. Let's first try these behaviors as unstable features. (I moved all implementations to unstable version of each API)

[kt3k]

(Unrelated side note: I initially thought it might be better to change our new feature policy (all feature should be unstable first) to land this PR directly, but somehow failed to invent a new policy. That delayed the review process/decision...)