This doesn't seem to work...: ```inline fun <re...

# strikt

[dave08]

This doesn't seem to work...:

inline fun <reified R> Assertion.Builder<Iterable<*>>.filterIsInstance(): DescribeableBuilder<List<R>> =
		get { filterIsInstance<R>() }

?

[dave08]

@robfletcher Any suggestions on how this could work? My test code is currently littered with replacements...

[dave08]

If I could get that working I could also avoid the single after it by making a filterSingleInstance after it... but then I don't know how to add the single assertion with reporting...

[robfletcher]

Will take a look shortly. Sitting in line at the DMV right now

[dave08]

Thanks!

[dave08]

I like the lib alot, but there's still quite a few assertions that could be added... and techniques for making certain types of assertions and filters could be added to the docs 🙂... Like I said, if I figure things out, I wouldn't mind PRing what I make, if you want.

[robfletcher]

Oh for sure. It’s only 6 months old!

[robfletcher]

That would be awesome. PRs and issues are very welcome.

[robfletcher]

I’m at work now. Will go over some of the Slack backlog at lunchtime

[dave08]

For 6 months, I think its better than most of what I've seen so far 😉!

[robfletcher]

Thanks

[dave08]

I tried again today... I really don't know what could be wrong with this... any ideas @robfletcher?

[dave08]

Sorry for bothering you, you're probably very busy...

[robfletcher]

I think without the generic type for the sub-type of Iterable that the other similar mapping functions have the compiler can’t find it unless you explicitly declare the subject to be Iterable<*>

[robfletcher]

Not sure how to resolve that while retaining the reified parameter, otherwise you have to specify all of the types

[dave08]

Funny that in stdlib:

public inline fun <reified R> Iterable<*>.filterIsInstance(): List<@kotlin.internal.NoInfer R> {
    return filterIsInstanceTo(ArrayList<R>())
}

Does it work there because of NoInfer? I'm not great at generics 🙃

[robfletcher]

It’s because there genuinely is only one generic type

[robfletcher]

I don’t know what that NoInfer thing is tbh

[robfletcher]

If you declare your subject specifically to be Iterable<*> I think your function works but that’s the only way it will work

[dave08]

Meaning assertThat(result as Iterable<*>).filterIsInstance<List<Foo>>()?

[robfletcher]

right

[robfletcher]

I can make it work like this:

fun <T : Iterable<E>, E, R> Builder<T>.filterIsInstance(type: Class<R>): Builder<List<R>> =
  get { filterIsInstance(type) }

[robfletcher]

Giving

val subject = listOf(1, 2L, 3.0, 4)
    expectThat(subject)
      .filterIsInstance(Int::class.java)
      .containsExactly(1, 4)

[robfletcher]

but that’s not as nice syntactically

[dave08]

And not have an extension function over that to provide the Class?

[dave08]

Maybe both together could do the trick 🙂

[robfletcher]

but it would have to provide T and E as well

[robfletcher]

Then it ends up looking like

expectThat(subject as List<Number>)
      .filterIsInstance<List<Number>, Number, Int>()
      .containsExactly(1, 4)

[robfletcher]

which is even worse

[dave08]

That could be done with the reified with only two... but not nice either...

[robfletcher]

oh wait, I might have figured it out

[robfletcher]

crazy. I have the inline reified version working now but not the Java-y one

[robfletcher]

but the former calls the latter

[robfletcher]

there’s some boxing shenanigoats going on because I’m using Int::class.java I think

[robfletcher]

inline fun <reified R> Builder<out Iterable<*>>.filterIsInstance(): Builder<List<R>>

[robfletcher]

seems to be the magic declaration.

[robfletcher]

Note the out type bound

[dave08]

Oh, I thought about that one, I just forgot that it could be specified on the receiver 👍🏼. That opens a few doors for assertions and filters on homogeneous collections... 🎉

[dave08]

Thanks!

[robfletcher]

cool. I’ll do some more poking later and get this added (along with a general filter method) and cut a release. Gotta get some work done now though!

[robfletcher]

Hope that gets some stuff unblocked for you. (Are you in SA? Judging by time zone.)

[dave08]

It certainly does 😉. Running a bit late here now in Israel...

[robfletcher]

ah, that’s where you are. I was thinking South Africa.

[robfletcher]

have a good night

[dave08]

have a nice day!