Map.getOrElse: treat nulls as missing values.

libraries/stdlib/src/kotlin/collections/MapWithDefault.kt

@@ -17,7 +17,7 @@ public fun <K, V: Any> Map<K, V>.getOrImplicitDefault(key: K): V {
     if (this is MapWithDefault)
         return this.getOrImplicitDefault(key)
 
-    return getOrElse(key, { throw NoSuchElementException("Key $key is missing in the map.") })
+    return getOrElseNullable(key, { throw NoSuchElementException("Key $key is missing in the map.") })
 }
 
 @kotlin.jvm.JvmName("getOrImplicitDefaultNullable")
@@ -26,7 +26,7 @@ public fun <K, V> Map<K, V>.getOrImplicitDefault(key: K): V {
     if (this is MapWithDefault)
         return this.getOrImplicitDefault(key)
 
-    return getOrElse(key, { throw NoSuchElementException("Key $key is missing in the map.") })
+    return getOrElseNullable(key, { throw NoSuchElementException("Key $key is missing in the map.") })
 }
 
 /**
@@ -83,7 +83,7 @@ private class MapWithDefaultImpl<K, out V>(public override val map: Map<K,V>, pr
     override val values: Collection<V> get() = map.values
     override val entries: Set<Map.Entry<K, V>> get() = map.entries
 
-    override fun getOrImplicitDefault(key: K): V = map.getOrElse(key, { default(key) })
+    override fun getOrImplicitDefault(key: K): V = map.getOrElseNullable(key, { default(key) })
 }
 
 private class MutableMapWithDefaultImpl<K, V>(public override val map: MutableMap<K, V>, private val default: (key: K) -> V): MutableMapWithDefault<K, V> {
@@ -104,6 +104,6 @@ private class MutableMapWithDefaultImpl<K, V>(public override val map: MutableMa
     override fun putAll(m: Map<out K, V>) = map.putAll(m)
     override fun clear() = map.clear()
 
-    override fun getOrImplicitDefault(key: K): V = map.getOrElse(key, { default(key) })
+    override fun getOrImplicitDefault(key: K): V = map.getOrElseNullable(key, { default(key) })
 }
 

libraries/stdlib/src/kotlin/collections/Maps.kt

@@ -170,8 +170,16 @@ public fun <K, V> Map.Entry<K, V>.toPair(): Pair<K, V> = Pair(key, value)
  *
  * @sample test.collections.MapTest.getOrElse
  */
-@Deprecated("This function will change its behavior soon not to distinguish missing keys and keys mapped to nulls. To stick with the new behavior you can use get(key) with ?: operator after instead.")
 public inline fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V): V {
+    val value = get(key)
+    if (value == null) {
+        return defaultValue()
+    } else {
+        return value
+    }
+}
+
+internal inline fun <K, V> Map<K, V>.getOrElseNullable(key: K, defaultValue: () -> V): V {
     val value = get(key)
     if (value == null && !containsKey(key)) {
         return defaultValue()
@@ -180,6 +188,8 @@ public inline fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V): V {
     }
 }
 
+
+
 /**
  * Returns the value for the given key. If the key is not found in the map, calls the [defaultValue] function,
  * puts its result into the map under the given key and returns it.

libraries/stdlib/test/collections/MapTest.kt

@@ -20,6 +20,10 @@ class MapTest {
         val empty = mapOf<String, Int?>()
         val c = empty.getOrElse("") { null }
         assertEquals(null, c)
+
+        val nullable = mapOf(1 to null)
+        val d = nullable.getOrElse(1) { "x" }
+        assertEquals("x", d)
     }
 
     @test fun getOrImplicitDefault() {