["Request"] Ease NonEmptyCollection methods usage calling suspend

[christophejan]

What version are you currently using?

1.2.0

What would you like to see?

Currently, the following mapIndexedOnNonEmptyList method get a Suspension functions can be called only within coroutine body compilation error, but not mapIndexedOnStandardCollection :

suspend fun mySuspendFunction(index: Int, value: Int): Any = TODO()

suspend fun mapIndexedOnNonEmptyList() =
    nonEmptyListOf(1, 3, 7).mapIndexed { index: Int, value: Int -> mySuspendFunction(index, value) }

suspend fun mapIndexedOnStandardCollection() =
    listOf(1, 3, 7).mapIndexed { index: Int, value: Int -> mySuspendFunction(index, value) }

I would like to be able to use NonEmptyCollection methods in a suspend method definition the same way you can on standard collections.

(note that the standard collection behavior is due to inline method definition of Iterable<T>.mapIndexed)

Why?

I think that it would ease NonEmptyCollection usage (to avoid custom extensions or to avoid switching back on standard collections).

[serras]

The problem here is that NonEmptyCollection defines map and friends as member methods. We could define them as extension functions, but this has two drawbacks:

1. We cannot provide "direct" implementations for things like NonEmptyList,
2. We would break source compatibility, since now users would need to import map explicitly.

What do you think? Summoning also @nomisRev @raulraja @franciscodr to the conversation.

[nomisRev]

Hmm, we can not solve this for the NonEmptyCollection type itself, but I think we can solve it for the concrete APIs by doing what we did for map. This comes at the cost of more code in Arrow, but it doesn't impact the binary size afaik.

@Suppress("OVERRIDE_BY_INLINE")
public override inline fun <B> map(transform: (A) -> B): NonEmptyList<B> =
  NonEmptyList(transform(head), tail.map(transform))

This works for example, whilst map is also defined for NonEmptyCollection.

public suspend fun mySuspendFunction(value: Int): Int = TODO()

public suspend fun mapIndexedOnNonEmptyList(): NonEmptyList<Int> =
  nonEmptyListOf(1, 3, 7).map { value: Int -> mySuspendFunction(value) }

[christophejan]

Thank You @serras @nomisRev