From efc8f2c88aff5f617c7a1c070271fbf7e091dcdd Mon Sep 17 00:00:00 2001
From: Ilya Gorbunov <ilya.gorbunov@jetbrains.com>
Date: Fri, 13 May 2016 17:42:28 +0300
Subject: [PATCH] Provide extensions to copy maps. #KT-9108

---
 .../stdlib/src/kotlin/collections/Maps.kt     | 24 ++++++++++++
 libraries/stdlib/test/collections/MapTest.kt  | 38 ++++++++++++++-----
 .../reference-public-api/kotlin-stdlib.txt    |  3 ++
 3 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/libraries/stdlib/src/kotlin/collections/Maps.kt b/libraries/stdlib/src/kotlin/collections/Maps.kt
index 0135d7c5b4d..350b39ff6ca 100644
--- a/libraries/stdlib/src/kotlin/collections/Maps.kt
+++ b/libraries/stdlib/src/kotlin/collections/Maps.kt
@@ -438,6 +438,29 @@ public fun <K, V> Sequence<Pair<K, V>>.toMap(): Map<K, V> = toMap(LinkedHashMap<
 public fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destination: M): M
         = destination.apply { putAll(this@toMap) }
 
+/**
+ * Returns a new read-only map containing all key-value pairs from the original map.
+ *
+ * The returned map preserves the entry iteration order of the original map.
+ */
+public fun <K, V> Map<out K, V>.toMap(): Map<K, V> = when (size) {
+    0 -> emptyMap()
+    else -> toMutableMap()
+}
+
+/**
+ * Returns a new mutable map containing all key-value pairs from the original map.
+ *
+ * The returned map preserves the entry iteration order of the original map.
+ */
+public fun <K, V> Map<out K, V>.toMutableMap(): MutableMap<K, V> = LinkedHashMap(this)
+
+/**
+ * Populates and returns the [destination] mutable map with key-value pairs from the given map.
+ */
+public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M): M
+        = destination.apply { putAll(this@toMap) }
+
 /**
  * Creates a new read-only map by replacing or adding an entry to this map from a given key-value [pair].
  *
@@ -532,6 +555,7 @@ internal fun <K, V> Map<K, V>.optimizeReadOnlyMap() = when (size) {
     else -> this
 }
 
+// creates a singleton copy of map, if it there is specialization available in target platform
 @kotlin.jvm.JvmVersion
 internal fun <K, V> Map<K, V>.toSingletonMap(): Map<K, V>
         = with (entries.iterator().next()) { Collections.singletonMap(key, value) }
diff --git a/libraries/stdlib/test/collections/MapTest.kt b/libraries/stdlib/test/collections/MapTest.kt
index 723f101631c..ea1c3a4707e 100644
--- a/libraries/stdlib/test/collections/MapTest.kt
+++ b/libraries/stdlib/test/collections/MapTest.kt
@@ -162,18 +162,36 @@ class MapTest {
         assertEquals("Mells", m2["location2"])
     }
 
-    @test fun createUsingPairs() {
-        val map = mapOf(Pair("a", 1), Pair("b", 2))
-        assertEquals(2, map.size)
-        assertEquals(1, map["a"])
-        assertEquals(2, map["b"])
+    @test fun createFrom() {
+        val pairs = arrayOf("a" to 1, "b" to 2)
+        val expected = mapOf(*pairs)
+
+        assertEquals(expected, pairs.toMap())
+        assertEquals(expected, pairs.asIterable().toMap())
+        assertEquals(expected, pairs.asSequence().toMap())
+        assertEquals(expected, expected.toMap())
+
+        val mutableMap = expected.toMutableMap()
+        assertEquals(expected, mutableMap)
+        mutableMap += "c" to 3
+        assertNotEquals(expected, mutableMap)
     }
 
-    @test fun createFromIterable() {
-        val map = listOf(Pair("a", 1), Pair("b", 2)).toMap()
-        assertEquals(2, map.size)
-        assertEquals(1, map.get("a"))
-        assertEquals(2, map.get("b"))
+    @test fun populateTo() {
+        val pairs = arrayOf("a" to 1, "b" to 2)
+        val expected = mapOf(*pairs)
+
+        val linkedMap: LinkedHashMap<String, Int> = pairs.toMap(linkedMapOf())
+        assertEquals(expected, linkedMap)
+
+        val hashMap: HashMap<String, Int> = pairs.asIterable().toMap(hashMapOf())
+        assertEquals(expected, hashMap)
+
+        val mutableMap: MutableMap<String, Int> = pairs.asSequence().toMap(mutableMapOf())
+        assertEquals(expected, mutableMap)
+
+        val mutableMap2 = mutableMap.toMap(mutableMapOf())
+        assertEquals(expected, mutableMap2)
     }
 
     @test fun createWithSelector() {
diff --git a/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib.txt b/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib.txt
index a730c79df5b..1e816d68dfd 100644
--- a/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib.txt
+++ b/libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib.txt
@@ -1532,10 +1532,13 @@ public final class kotlin/collections/MapsKt {
 	public static final fun toList (Ljava/util/Map;)Ljava/util/List;
 	public static final fun toMap (Ljava/lang/Iterable;)Ljava/util/Map;
 	public static final fun toMap (Ljava/lang/Iterable;Ljava/util/Map;)Ljava/util/Map;
+	public static final fun toMap (Ljava/util/Map;)Ljava/util/Map;
+	public static final fun toMap (Ljava/util/Map;Ljava/util/Map;)Ljava/util/Map;
 	public static final fun toMap (Lkotlin/sequences/Sequence;)Ljava/util/Map;
 	public static final fun toMap (Lkotlin/sequences/Sequence;Ljava/util/Map;)Ljava/util/Map;
 	public static final fun toMap ([Lkotlin/Pair;)Ljava/util/Map;
 	public static final fun toMap ([Lkotlin/Pair;Ljava/util/Map;)Ljava/util/Map;
+	public static final fun toMutableMap (Ljava/util/Map;)Ljava/util/Map;
 	public static final fun toSortedMap (Ljava/util/Map;)Ljava/util/SortedMap;
 	public static final fun toSortedMap (Ljava/util/Map;Ljava/util/Comparator;)Ljava/util/SortedMap;
 	public static final fun withDefault (Ljava/util/Map;Lkotlin/jvm/functions/Function1;)Ljava/util/Map;