Add mutable Map.updateWith

compat/src/main/scala-2.11_2.12/scala/collection/compat/PackageShared.scala

@@ -271,6 +271,10 @@ private[compat] trait PackageShared {
  self: scala.collection.Map[K, V]): MapExtensionMethods[K, V] =
  new MapExtensionMethods[K, V](self)
 
+ implicit def toMutableMapExtensionMethods[K, V](
+ self: scala.collection.mutable.Map[K, V]): MutableMapExtensionMethods[K, V] =
+ new MutableMapExtensionMethods[K, V](self)
+
  implicit def toMapViewExtensionMethods[K, V, C <: scala.collection.Map[K, V]](
  self: IterableView[(K, V), C]): MapViewExtensionMethods[K, V, C] =
  new MapViewExtensionMethods[K, V, C](self)
@@ -523,6 +527,19 @@ class MapExtensionMethods[K, V](private val self: scala.collection.Map[K, V]) ex
 
 }
 
+class MutableMapExtensionMethods[K, V](private val self: scala.collection.mutable.Map[K, V])
+ extends AnyVal {
+
+ def updateWith(key: K)(remappingFunction: (Option[V]) => Option[V]): Option[V] = {
+ val updatedEntry = remappingFunction(self.get(key))
+ updatedEntry match {
+ case Some(v) => self.update(key, v)
+ case None => self.remove(key)
+ }
+ updatedEntry
+ }
+}
+
 class MapViewExtensionMethods[K, V, C <: scala.collection.Map[K, V]](
  private val self: IterableView[(K, V), C])
  extends AnyVal {

compat/src/test/scala/test/scala/collection/MutableMapTest.scala

@@ -0,0 +1,38 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package test.scala.collection
+
+import org.junit.Test
+import org.junit.Assert._
+
+import scala.collection.compat._
+import scala.collection.{mutable => m}
+
+class MutableMapTest {
+
+ @Test
+ def updateWith: Unit = {
+ val map = m.Map("a" -> 1, "c" -> 3)
+ map.updateWith("b") {
+ case None => Some(2)
+ case Some(x) => Some(-1)
+ }
+ map.updateWith("c") {
+ case None => Some(-1)
+ case Some(_) => None
+ }
+ assertEquals(map.get("b"), Some(2))
+ assertFalse(map.contains("c"))
+ }
+
+}