Hey everyone, I’m wondering if anyone has had this...

# arrow-contributors

[pablisco]

Hey everyone, I’m wondering if anyone has had this issue before and how to resolve it.
I’m creating a new module in the arrow-fx project and I need to target jdk8.
I’ve changed the dependency to kotlin to use kotlin-stdlib-jdk8 and I’ve added the following:

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

sourceCompatibility = "1.8"
targetCompatibility = "1.8"

I wasn’t sure if I needed both (kotlin and java compatibility markers) but I was trying to make it work.

I’ve even changed JAVA_VERSION to be 1.8 on the modules gradle.properties file.

Any who, despite all these changes, I’m getting the following errors from Animal Sniffer:

[Undefined reference] arrow.fx.(_IO.kt:19)
  >> boolean java.util.concurrent.CompletableFuture.complete(Object)

[Undefined reference] arrow.fx.(_IO.kt:20)
  >> boolean java.util.concurrent.CompletableFuture.completeExceptionally(Throwable)

[Undefined reference] arrow.fx.(_IO.kt:21)
  >> boolean java.util.concurrent.CompletableFuture.completeExceptionally(Throwable)

[Undefined reference] arrow.fx.(_IO.kt:8)
  >> Object java.util.concurrent.CompletableFuture.get()

[Undefined reference] arrow.fx.(_IO.kt:16)
  >> java.util.concurrent.CompletableFuture

[Undefined reference] arrow.fx.(_IO.kt:16)
  >> void java.util.concurrent.CompletableFuture.<init>()

[Undefined reference] arrow.fx.(_IO.kt:12)
  >> boolean java.util.concurrent.CompletableFuture.cancel(boolean)

I’m having a look at this ticket: https://github.com/arrow-kt/arrow-fx/issues/153
These APIs were introduced on the jdk8, so this module needs to target that version (hence why it’s a separate module)
Anyone has experienced on how to configure animal sniffer in this instance?

If you want to check it locally this is the branch: https://github.com/arrow-kt/arrow-fx/tree/pabs-completable-future-integration

[stojan]

this is what I have in my Android project

compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    // For Kotlin projects
    kotlinOptions {
        jvmTarget = "1.8"
    }

[stojan]

not sure if it helps 🙂

[pablisco]

Thanks for the suggestion. However, I think that those are inside the android { } closure, right? This is a plain kotlin.

[stojan]

yup...

[stojan]

IMO it's time for arrow to move to Java8 min

[pablisco]

That’s probably not a bad idea. Android (I think was the reason to keep it on 7) has great support for j8. And we can check for bytecode compatibility for Android 24, which is when CompletableFuture was introduced fully to Android.

[pablisco]

Tat said I think we are checking against version 21 as defined on the root build script:
https://github.com/arrow-kt/arrow-fx/blob/pabs-completable-future-integration/build.gradle#L38

[pablisco]

And I think I just found the source of the problem 🎉

[stojan]

at work we have been targeting Java8 bytecode since forever.... no problems at all

[pablisco]

Yeah, should be ok. We should still check bytecode compatibility with Android SDK 21 though, as it supports a subset of what’s available in J8.
It would be interesting to see if there is any performance benefits at compile and runtime 🤔
I’ve created this ticket: https://github.com/arrow-kt/arrow/issues/2138

[pablisco]

Also, for reference, this is the fix for animal sniffer:
https://github.com/arrow-kt/arrow-fx/commit/f529f3190d003028712a0074ab1345e79fb90e06