Have been trying to do some testing on a place whe...

# apollo-kotlin

[Stylianos Gakis]

Have been trying to do some testing on a place where I’m also using an ApolloClient + QueueTestNetworkTransport + test builders + parameterized tests, and got a question mostly for how to work with the test builders here.
The real code is here, but the gist of what I am not finding a way to make it work nice is that I want my parameterized input to be a map of SomeType -> ExpectedResult. and then I need to somehow make that work with the test builder. The test builder doesn’t take in the type itself, since it uses its own DSL, so I am doing something silly like having my parameter be of the type I actually want to get from the apollo call, and then I map it to the buildBlahBlah that I need, like

FooQuery.Data {
  status = when(parameterizedInput) {
    1 -> buildBlah {}
    2 -> buildOtherBlah {}
  }
}

But it’s quite inconvenient I think, I wonder if there’s something better I can do here.

[Stylianos Gakis]

Hmmm actually I couldn’t get it to work before, but doing this also works

override fun provideValues(): List<Pair<BuilderScope.() -> ContractStatusMap, IsAllowedToTerminateContract>> {
  return listOf<Pair<BuilderScope.() -> ContractStatusMap, IsAllowedToTerminateContract>>(
    { it: BuilderScope -> it.buildPendingStatus {} } to IsAllowedToTerminateContract.ALLOWED,
  )
}

The trick is that in the lambda I am creating, inference does not just work and I need to very explicitly say that the receiver inside the lambda is of type BuilderScope with the { it: BuilderScope -> part which I’ve never had to do before I think. This gives it access to the buildFoo() function, otherwise it was just red even if I explicitly set the type in the listOf<>() call.
Very very interesting. I think this is the way to go then, my parameterized input can be a lambda which I can use inside the builder. Just a bit tricky to get that lambda right, but it does work 😅

[bod]

Ah interesting! I was gonna say, maybe something with the parameters being a lambda, but not exactly sure how/what 🙂

[Stylianos Gakis]

Yeah I tried this initially, but it just wouldn’t let me resolve the function, so I figured it wouldn’t work. But this does, while looking super odd tbh with the explicit type there 😅
I thought it’d be able to pick that up from the fact that the list is explicitly typed with the BuilderScope.() -> ContractStatusMap but no, the lambda does not see BuilderScope in there unless I explicitly put it there with it: BuilderScope ->

[bod]

a bit odd indeed 🙂

[bod]

I guess sometimes the compiler needs a little help 😅

[Stylianos Gakis]

https://github.com/HedvigInsurance/android/pull/1767/commits/0b49776bad250312ac1f273291d0b32fe062b5cc Much cleaner 🧹

[bod]

actually I'm confused, shouldn't it be BuilderScope -> ContractStatusMap instead of BuilderScope.() -> ContractStatusMap ?

[Stylianos Gakis]

It’s a function lambda, so it either has to be BuilderScope.() -> ContractStatusMap or (BuilderScope) -> ContractStatusMap right?
In either case, the compiler can use either one of them interchangeably in this context as far as I can tell.
It’s just that in the lambda itself I can’t somehow denote that it’s BuilderScope.() -> ContractStatusMap so I pass it as it which would mean that it’s like (BuilderScope) -> ContractStatusMap yeah.
But yeah, it knows how to figure out “`T.() -> Unit` <-> `(T) -> Unit`” by itself.

[Stylianos Gakis]

Magic 🪄

[Stylianos Gakis]

Isn’t it perhaps somewhat related to how on the JVM they got the same (I think?) signature? I think extension functions when called by Java callers you simply pass the receiver as the first parameter and it works right?

[bod]

Woops you're right, I meant (BuilderScope) -> ContractStatusMap

But still something I don't get, e.g.

val lambda1: (String) -> Int = { it: String -> it.toInt() }
val lambda2: String.() -> Int = { it: String -> it.toInt() }

lambda2 doesn't compile for me

[bod]

but:

val listOfLambda1 = listOf<(String) -> Int>({ it: String -> it.toInt() })
val listOfLambda2 = listOf<String.() -> Int>({ it: String -> it.toInt() })

does compile.

🪄 indeed

[Stylianos Gakis]

Haha yeah that’s a bit crazy is it not 😅
And you do also see that if you do not add the it: String -> there you do not get the String as a receiver in the lambda right?

[bod]

in my case

val listOfLambda2 = listOf<String.() -> Int>({ this.toInt() })

also compiles

[bod]

but we probably stumbled on a quirk :)

[bod]

something for those "Kotlin Puzzlers" talks 😄

[Stylianos Gakis]

“Puzzled” is definitely an adjective that describes me right now yeah 😅