=lib Make use of CompletionStage#handle instead of CompletionStage#wh…

…enComplete for better performance.
scala · Nov 8, 2022 · a4a2031 · a4a2031
1 parent 4886921
commit a4a2031
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Showing 3 changed files with 16 additions and 5 deletions.
diff --git a/project/MimaFilters.scala b/project/MimaFilters.scala
@@ -31,6 +31,13 @@ object MimaFilters extends AutoPlugin {
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.Predef#ArrayCharSequence.isEmpty"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.runtime.ArrayCharSequence.isEmpty"),
 
+    // KEEP: make use of CompletionStage#handle to get a better performance than CompletionStage#whenComplete.
+    ProblemFilters.exclude[MissingTypesProblem]("scala.concurrent.impl.FutureConvertersImpl$P"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.concurrent.impl.FutureConvertersImpl#P.andThen"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.concurrent.impl.FutureConvertersImpl#P.apply"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("scala.concurrent.impl.FutureConvertersImpl#P.andThen"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.concurrent.impl.FutureConvertersImpl#P.accept"),
+    ProblemFilters.exclude[IncompatibleMethTypeProblem]("scala.concurrent.impl.FutureConvertersImpl#P.andThen"),
   )
 
   override val buildSettings = Seq(

diff --git a/src/library/scala/concurrent/impl/FutureConvertersImpl.scala b/src/library/scala/concurrent/impl/FutureConvertersImpl.scala
@@ -91,8 +91,8 @@ private[scala] object FutureConvertersImpl {
     override def toString(): String = super[CompletableFuture].toString
   }
 
-  final class P[T](val wrapped: CompletionStage[T]) extends DefaultPromise[T] with BiConsumer[T, Throwable] {
-    override def accept(v: T, e: Throwable): Unit = {
+  final class P[T](val wrapped: CompletionStage[T]) extends DefaultPromise[T] with BiFunction[T, Throwable, Unit] {
+    override def apply(v: T, e: Throwable): Unit = {
       if (e == null) success(v)
       else failure(e)
     }

diff --git a/src/library/scala/jdk/javaapi/FutureConverters.scala b/src/library/scala/jdk/javaapi/FutureConverters.scala
@@ -12,10 +12,10 @@
 
 package scala.jdk.javaapi
 
-import java.util.concurrent.CompletionStage
-
+import java.util.concurrent.{CompletableFuture, CompletionStage}
 import scala.concurrent.impl.FutureConvertersImpl.{CF, P}
 import scala.concurrent.{ExecutionContext, Future}
+import scala.util.Success
 
 /** This object contains methods that convert between Scala [[scala.concurrent.Future]] and Java [[java.util.concurrent.CompletionStage]].
   *
@@ -70,9 +70,13 @@ object FutureConverters {
       case cf: CF[T] => cf.wrapped
       // in theory not safe (could be `class C extends Future[A] with CompletionStage[B]`):
       case f: Future[T @unchecked] => f
+      case cf: CompletableFuture[T @unchecked] if cf.isDone && !cf.isCompletedExceptionally =>
+        val p = new P[T](cs)
+        p.tryComplete(Success(cf.join()))
+        p.future
       case _ =>
         val p = new P[T](cs)
-        cs whenComplete p
+        cs.handle(p)
         p.future
     }
   }