Coroutines compatibility module

build.sbt

@@ -22,13 +22,39 @@ inThisBuild(
     )
 )
 
-lazy val root = (project in file("."))
+lazy val core = (project in file("core"))
+  .enablePlugins(KotlinPlugin)
+  .settings(
+      organization := "io.github.leviysoft",
+      name := "scala-kotlin-compat",
+      kotlinVersion := "1.9.25",
+      kotlincJvmTarget := "11",
+      kotlincOptions += "-Xjvm-default=all",
+      kotlinLib("stdlib")
+  )
+
+lazy val coroutines = (project in file("coroutines"))
   .enablePlugins(KotlinPlugin)
   .settings(
     organization := "io.github.leviysoft",
-    name := "scala-kotlin-compat",
+    name := "scala-kotlin-coroutines-compat",
     kotlinVersion := "1.9.25",
     kotlincJvmTarget := "11",
     kotlincOptions += "-Xjvm-default=all",
-    kotlinLib("stdlib")
+    kotlinLib("stdlib"),
+    libraryDependencies ++= Seq(
+      "org.jetbrains.kotlinx" % "kotlinx-coroutines-core" % "1.8.1",
+      "com.github.sbt" % "junit-interface" % "0.13.3" % Test,
+      "org.jetbrains.kotlin" % "kotlin-test-junit" % kotlinVersion.value % Test
+    )
+  )
+
+lazy val root = (project in file("."))
+  .dependsOn(core, coroutines)
+  .aggregate(core, coroutines)
+  .settings(
+      crossScalaVersions := Nil,
+      publish := {},
+      publishArtifact := false,
+      publish / skip := true
   )

coroutines/src/main/kotlin/com/github/leviysoft/sk/coroutines/CoroutineScalaConversions.kt

@@ -0,0 +1,76 @@
+@file:OptIn(InternalCoroutinesApi::class, ExperimentalCoroutinesApi::class)
+
+package com.github.leviysoft.sk.coroutines
+
+import kotlinx.coroutines.*
+
+import kotlin.coroutines.CoroutineContext
+import kotlin.coroutines.EmptyCoroutineContext
+import scala.concurrent.ExecutionContext
+import scala.concurrent.Future
+import scala.concurrent.Promise
+import scala.util.Failure
+import scala.util.Success
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
+
+fun <T> CoroutineScope.scalaFuture(
+    context: CoroutineContext = EmptyCoroutineContext,
+    start: CoroutineStart = CoroutineStart.DEFAULT,
+    block: suspend CoroutineScope.() -> T
+) : Future<T> {
+    require(!start.isLazy) { "$start start is not supported" }
+    val newContext = this.newCoroutineContext(context)
+    val promise = Promise.apply<T>()
+    val coroutine = PromiseCoroutine(newContext, promise)
+    coroutine.start(start, coroutine, block)
+
+    return promise.future()
+}
+
+fun <T> Deferred<T>.asScalaFuture(): Future<T> {
+    val promise: Promise<T> = Promise.apply()
+
+    invokeOnCompletion {
+        try {
+            promise.success(getCompleted())
+        } catch (t: Throwable) {
+            promise.failure(t)
+        }
+    }
+
+    return promise.future()
+}
+
+fun Job.asScalaFuture(): Future<scala.runtime.BoxedUnit> {
+    val promise: Promise<scala.runtime.BoxedUnit> = Promise.apply()
+    invokeOnCompletion { cause ->
+        if (cause === null) promise.success(scala.runtime.BoxedUnit.UNIT)
+        else promise.failure(cause)
+    }
+    return promise.future()
+}
+
+fun <T> Future<T>.asDeferred(executor: ExecutionContext): Deferred<T> {
+    val result = CompletableDeferred<T>()
+    this.onComplete({ res ->
+        when(res) {
+            is Success -> result.complete(res.value())
+            is Failure -> result.completeExceptionally(res.exception())
+            else -> throw IllegalStateException("Unreachable")
+        }
+    }, executor)
+    return result
+}
+
+suspend fun <T> Future<T>.await(executor: ExecutionContext): T {
+    return suspendCancellableCoroutine { cont: CancellableContinuation<T> ->
+        this.onComplete({ res ->
+            when(res) {
+                is Success -> cont.resume(res.value())
+                is Failure -> cont.resumeWithException(res.exception())
+                else -> throw IllegalStateException("Unreachable")
+            }
+        }, executor)
+    }
+}

coroutines/src/main/kotlin/com/github/leviysoft/sk/coroutines/PromiseCoroutine.kt

@@ -0,0 +1,17 @@
+package com.github.leviysoft.sk.coroutines
+
+import kotlinx.coroutines.AbstractCoroutine
+import kotlinx.coroutines.InternalCoroutinesApi
+import scala.concurrent.Promise
+import kotlin.coroutines.CoroutineContext
+
+@OptIn(InternalCoroutinesApi::class)
+internal class PromiseCoroutine<T>(context: CoroutineContext, private val promise: Promise<T>): AbstractCoroutine<T>(context, initParentJob = true, active = true) {
+    override fun onCompleted(value: T) {
+        this.promise.success(value)
+    }
+
+    override fun onCancelled(cause: Throwable, handled: Boolean) {
+        this.promise.failure(cause)
+    }
+}

coroutines/src/test/kotlin/com/github/leviysoft/sk/coroutines/FutureConversionTests.kt

@@ -0,0 +1,20 @@
+package com.github.leviysoft.sk.coroutines
+
+import kotlinx.coroutines.runBlocking
+import scala.concurrent.ExecutionContext
+import scala.concurrent.`Future$`
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class FutureConversionTests {
+    @Test
+    fun awaitFutureTest() {
+        val future = `Future$`.`MODULE$`.successful(42)
+
+        val result = runBlocking {
+            future.await(ExecutionContext.global())
+        }
+
+        assertEquals(42, result)
+    }
+}

readme.md

@@ -16,4 +16,5 @@ The following components of `scala.jdk` are implemented:
 - [x] FutureConverters
 - [x] OptionConverters
 - [ ] StreamConverters
-
+
+In addition, `scala-kotlin-coroutines-compat` provides utilities for calling `suspend fun`s as `Future`s