Merge pull request scala#220 from szeiger/issue/203

Add mapValues for IterableViews of Maps

Author: julienrf

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

@@ -14,7 +14,7 @@ package scala.collection.compat
 
 import scala.collection.generic._
 import scala.reflect.ClassTag
-import scala.collection.{MapLike, GenTraversable, BitSet}
+import scala.collection.{MapLike, GenTraversable, BitSet, IterableView}
 import scala.collection.{immutable => i, mutable => m}
 import scala.{collection => c}
 
@@ -155,6 +155,9 @@ private[compat] trait PackageShared {
   // in scala-library so we can't add to it
   type IterableOnce[+X] = c.TraversableOnce[X]
   val IterableOnce = c.TraversableOnce
+
+  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)
 }
 
 class ImmutableSortedMapExtensions(private val fact: i.SortedMap.type) extends AnyVal {
@@ -231,3 +234,8 @@ class TraversableOnceExtensionMethods[A](private val self: c.TraversableOnce[A])
 class TraversableExtensionMethods[A](private val self: c.Traversable[A]) extends AnyVal {
   def iterableFactory: GenericCompanion[Traversable] = self.companion
 }
+
+class MapViewExtensionMethods[K, V, C <: scala.collection.Map[K, V]](private val self: IterableView[(K, V), C]) extends AnyVal {
+  def mapValues[W, That](f: V => W)(implicit bf: CanBuildFrom[IterableView[(K, V), C], (K, W), That]): That =
+    self.map[(K, W), That] { case (k, v) => (k, f(v)) }
+}

compat/src/test/scala/test/scala/collection/ViewTest.scala

@@ -0,0 +1,30 @@
+/*
+ * 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._
+
+class ViewTest {
+
+  @Test
+  def mapValues: Unit = {
+    val m = Map("a" -> 1, "b" -> 2, "c" -> 3)
+    val oldStyle = m.mapValues(x => x*x)
+    val newStyle = m.view.mapValues(x => x*x)
+    assertEquals(oldStyle.toMap, newStyle.toMap)
+  }
+
+}