Merge pull request #10027 from som-snytt/issue/12586

Java ConcurrentMap wrapper updateWith is compute

project/MimaFilters.scala

@@ -36,6 +36,9 @@ object MimaFilters extends AutoPlugin {
     ProblemFilters.exclude[MissingClassProblem]("scala.runtime.PStatics"),  // private[scala]
     ProblemFilters.exclude[MissingClassProblem]("scala.runtime.PStatics$"), // private[scala]
 
+    // internal to wrappers
+    ProblemFilters.exclude[NewMixinForwarderProblem]("scala.collection.convert.JavaCollectionWrappers#JMapWrapperLike.getOrElseUpdate"),
+    ProblemFilters.exclude[NewMixinForwarderProblem]("scala.collection.convert.JavaCollectionWrappers#JMapWrapperLike.updateWith"),
   )
 
   override val buildSettings = Seq(

src/library/scala/collection/convert/JavaCollectionWrappers.scala

@@ -332,6 +332,7 @@ private[collection] object JavaCollectionWrappers extends Serializable {
       else
         None
     }
+    override def getOrElseUpdate(key: K, op: => V): V = underlying.computeIfAbsent(key, _ => op)
 
     def addOne(kv: (K, V)): this.type = { underlying.put(kv._1, kv._2); this }
     def subtractOne(key: K): this.type = { underlying remove key; this }
@@ -354,6 +355,10 @@ private[collection] object JavaCollectionWrappers extends Serializable {
 
     override def update(k: K, v: V): Unit = underlying.put(k, v)
 
+    override def updateWith(key: K)(remappingFunction: Option[V] => Option[V]): Option[V] = Option {
+      underlying.compute(key, (_, v) => remappingFunction(Option(v)).getOrElse(null.asInstanceOf[V]))
+    }
+
     // support Some(null) if currently bound to null
     override def remove(k: K): Option[V] = {
       var result: Option[V] = None
@@ -434,6 +439,8 @@ private[collection] object JavaCollectionWrappers extends Serializable {
 
     override def get(k: K) = Option(underlying get k)
 
+    override def getOrElseUpdate(key: K, op: => V): V = underlying.computeIfAbsent(key, _ => op)
+
     override def isEmpty: Boolean = underlying.isEmpty
     override def knownSize: Int = if (underlying.isEmpty) 0 else super.knownSize
     override def empty = new JConcurrentMapWrapper(new juc.ConcurrentHashMap[K, V])
@@ -452,6 +459,10 @@ private[collection] object JavaCollectionWrappers extends Serializable {
         case _ if isEmpty => None
         case _ => Try(last).toOption
       }
+
+    override def updateWith(key: K)(remappingFunction: Option[V] => Option[V]): Option[V] = Option {
+      underlying.compute(key, (_, v) => remappingFunction(Option(v)).getOrElse(null.asInstanceOf[V]))
+    }
   }
 
   @SerialVersionUID(3L)

test/junit/scala/collection/convert/MapWrapperTest.scala

@@ -1,13 +1,14 @@
 package scala.collection.convert
 
-import java.util
+import java.{util => jutil}
 
 import org.junit.Assert._
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
 
 import scala.jdk.CollectionConverters._
+import scala.util.chaining._
 
 @RunWith(classOf[JUnit4])
 class MapWrapperTest {
@@ -63,7 +64,7 @@ class MapWrapperTest {
   // regression test for https://github.com/scala/bug/issues/10663
   @Test
   def testHashCodeEqualsMatchesJavaMap(): Unit = {
-    val jmap = new util.HashMap[String, String]()
+    val jmap = new jutil.HashMap[String, String]()
     jmap.put("scala", "rocks")
     jmap.put("java interop is fun!", "ya!")
     jmap.put("Ĺởồҝ ïŧ\\'ş ūŋǐčōđẹ", "whyyyy")
@@ -79,4 +80,31 @@ class MapWrapperTest {
     assertTrue(jmap == mapWrapper)
     assertTrue(mapWrapper == jmap)
   }
+
+  // was: induce intermittent failure due to contention, where updater is called more than once
+  @Test def `t12586 updateWith should delegate to compute`: Unit = {
+    val limit = 100      // retries until trigger
+    @volatile var count = 0
+    val jmap = new jutil.concurrent.ConcurrentHashMap[String, String]()
+    class Loki extends Runnable {
+      @volatile var done = false
+      def run(): Unit = {
+        while (!done) {
+          jmap.put("KEY", "VALUE")
+          //Thread.`yield`()
+        }
+      }
+    }
+    val loki = new Loki
+    val runner = new Thread(loki).tap(_.start)
+    val wrapped = jmap.asScala
+    def updater(old: Option[String]) = { count += 1 ; old.map(_ * 2) }
+    for (i <- 1 to limit) {
+      count = 0
+      wrapped.updateWith("KEY")(updater)
+      assertEquals(s"index $i", 1, count)
+    }
+    loki.done = true
+    runner.join()
+  }
 }