[BUG] `Array.groupWhen` returns an empty array if the predicate never returns `true`

[omaus]

Description

Array.groupWhen returns an empty array if the predicate never returns true.

Repro steps

1. Use this exemplary code in a script environment:

   let isOdd = n % 2 <> 0
   Array.groupWhen isOdd [|4;4;2;4;0;2|]

2. Run the code

Expected behavior

Returns [|[|4;4;2;4;0;2|]|]

Actual behavior

Returns [|[||]|]

Known workarounds

Introduce a case where the predicate returns true. Not well applicable.

Related information

• Operating system: Win10 Home64bit
• main
• .NET Runtime, CoreCLR or Mono Version: 5.0.403

[kMutagene]

Might be arguing about semantics, but this is the correct output i would expect from groupWhen. It opens a new group only if the predicate is true.

[omaus]

No, imo it is not. No grouping applied does, imo, not mean that you get nothing back but that the original, unseparated group is returned as the only resulting subgroup.
Seq.groupWhen and List.groupWhen behave as expected (by me).

Seq.groupWhen isOdd [|6; 6; 2; 4; 2; 8|] // val it: seq<seq<int>> = seq [[6; 6; 2; 4; 2; 8]]
List.groupWhen isOdd [6; 6; 2; 4; 2; 8] // val it: int list list = [[6; 6; 2; 4; 2; 8]]

[kMutagene]

i stand overruled.