Scala 3 Support, helper syntax for MapK.apply, override equals/hashCode

Author: dylemma

build.sbt

@@ -1,15 +1,22 @@
 name := "mapk"
-version := "1.1.0"
+version := "1.2.0"
 
-scalaVersion := "2.12.13"
-crossScalaVersions := List("2.12.13", "2.13.5")
-scalacOptions := List("-deprecation", "-unchecked", "-feature", "-language:higherKinds")
-scalacOptions ++= (scalaBinaryVersion.value match {
-	case "2.12" => Seq("-Ypartial-unification")
+scalaVersion := "2.12.14"
+crossScalaVersions := List("2.12.14", "2.13.6", "3.0.0")
+
+libraryDependencies += "org.typelevel" %% "cats-core" % "2.6.1"
+libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.9" % "test"
+libraryDependencies ++= (scalaBinaryVersion.value match {
+	case "2.12" | "2.13" => compilerPlugin("org.typelevel" % "kind-projector" % "0.13.0" cross CrossVersion.full) :: Nil
 	case _ => Nil
 })
 
-libraryDependencies += "org.typelevel" %% "cats-core" % "2.4.2"
-libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.5" % "test"
-
-addCompilerPlugin("org.typelevel" % "kind-projector" % "0.11.3" cross CrossVersion.full)
+scalacOptions := List("-deprecation", "-unchecked", "-feature", "-language:higherKinds")
+scalacOptions ++= {
+	CrossVersion.partialVersion(scalaVersion.value) match {
+		case Some((2, 12)) => Seq("-Ypartial-unification", "-Xsource:3")
+		case Some((2, 13)) => Seq("-Xsource:3")
+		case Some((3, _)) => Seq("-Ykind-projector")
+		case _ => Nil
+	}
+}

project/build.properties

@@ -1 +1 @@
-sbt.version=1.4.3
+sbt.version=1.5.2

readme.md

@@ -16,6 +16,10 @@ val info: MapK[MyKey, cats.Id] = MapK.empty[MyKey, cats.Id]
    .updated(Age, 21)
    .updated(Name, "Dylan")
 
+// alternate apply syntax:
+import MapK.entrySyntax._
+val info = MapK(Age ~>> 21, Name ~>> "Dylan")
+
 val age: Option[Int] = info.get(Age) // Some(21)
 val name: Option[String] = info.get(Name) // Some("Dylan")
 val numThings: Option[Int] = info.get(NumThings) // None

src/main/scala/com/codedx/util/MapK.scala

@@ -21,52 +21,60 @@ import cats.arrow.FunctionK
 import cats.data.Tuple2K
 import cats.{ Monoid, SemigroupK, ~> }
 
-class MapK[K[_], V[_]] private[MapK](val untyped: Map[K[_], V[_]]) { self =>
+class MapK[K[*], V[*]] private[MapK](val untyped: Map[K[Any], V[Any]]) { self =>
 	type Entry[x] = (K[x], V[x])
 	type Combiner[x] = (V[x], V[x]) => V[x]
 
-	def contains(key: K[_]): Boolean = untyped.contains(key)
-	def get[T](key: K[T]): Option[V[T]] = untyped.get(key).map(_.asInstanceOf[V[T]])
-	def apply[T](key: K[T]): V[T] = untyped(key).asInstanceOf[V[T]]
-	def +[T](key: K[T], value: V[T]): MapK[K, V] = new MapK[K, V](untyped + (key -> value))
+	override def equals(obj: Any): Boolean = obj match {
+		case that: MapK[?, ?] => this.untyped == that.untyped
+		case _ => false
+	}
+	override def hashCode(): Int = untyped.hashCode()
+
+	@inline private def asAny[X[_], A](x: X[A]): X[Any] = x.asInstanceOf[X[Any]]
+
+	def contains[A](key: K[A]): Boolean = untyped.contains(asAny(key))
+	def get[T](key: K[T]): Option[V[T]] = untyped.get(asAny(key)).map(_.asInstanceOf[V[T]])
+	def apply[T](key: K[T]): V[T] = untyped(asAny(key)).asInstanceOf[V[T]]
+	def +[T](key: K[T], value: V[T]): MapK[K, V] = new MapK[K, V](untyped + (asAny(key) -> asAny(value)))
 	def updated[T](key: K[T], value: V[T]): MapK[K, V] = this.+(key, value)
 	def ++(that: MapK[K, V]): MapK[K, V] = {
-		val out = Map.newBuilder[K[_], V[_]]
-		val add = new FunctionK[Entry, Lambda[x => Unit]] {
-			def apply[A](fa: (K[A], V[A])): Unit = out += fa
+		val out = Map.newBuilder[K[Any], V[Any]]
+		val add = new FunctionK[Entry, ({ type U[x] = Unit })#U] {
+			def apply[A](fa: (K[A], V[A])): Unit = out += (asAny(fa._1) -> asAny(fa._2))
 		}
 		this.foreach(add)
 		that.foreach(add)
 		new MapK[K, V](out.result())
 	}
-	def foreach(f: Entry ~> Lambda[x => Unit]): Unit = {
-		for ((key, value) <- untyped) {
-			val t = MapK.tuple(key, value)
-			f(t)
-		}
+	def foreach(f: Entry ~> ({ type U[x] = Unit })#U): Unit = {
+		def handleKv[A](kv: (K[Any], V[Any])) = f(MapK.tuple(kv._1.asInstanceOf[K[A]], kv._2.asInstanceOf[V[A]]))
+		for (kv <- untyped) handleKv(kv)
 	}
 	def mapValues[V2[_]](f: V ~> V2): MapK[K, V2] = {
-		val mapped = Map.newBuilder[K[_], V2[_]]
-		for((k, v) <- untyped) mapped += (k -> f(v))
+		val mapped = Map.newBuilder[K[Any], V2[Any]]
+		def handleKv[A](kv: (K[Any], V[Any])): Unit = mapped += (kv._1.asInstanceOf[K[Any]] -> asAny(f(kv._2.asInstanceOf[V[A]])))
+		for(kv <- untyped) handleKv(kv)
 		MapK.coerce[K, V2](mapped.result())
 	}
 	def map[V2[_]](f: Entry ~> V2): MapK[K, V2] = {
-		val mapped = Map.newBuilder[K[_], V2[_]]
-		for((k, v) <- untyped) mapped += (k -> f(MapK.tuple(k, v)))
+		val mapped = Map.newBuilder[K[Any], V2[Any]]
+		def handleKv[A](kv: (K[Any], V[Any])) = mapped += (kv._1.asInstanceOf[K[Any]] -> f(MapK.tuple[K, V, A](kv._1.asInstanceOf[K[A]], kv._2.asInstanceOf[V[A]])).asInstanceOf[V2[Any]])
+		for(kv <- untyped) handleKv(kv)
 		MapK.coerce[K, V2](mapped.result())
 	}
-	def keys: Iterable[K[_]] = untyped.keys
+	def keys: Iterable[K[Any]] = untyped.keys
 
 	def merge(that: MapK[K, V], combiner: K ~> Combiner): MapK[K, V] = {
 		var out: MapK[K, V] = self
-		that.foreach(new FunctionK[that.Entry, Lambda[x => Unit]] {
+		that.foreach(new FunctionK[that.Entry, ({ type U[x] = Unit })#U] {
 			def apply[A](kv: (K[A], V[A])): Unit = {
 				val (k, newValue) = kv
 				val v2 = self.get(k) match {
 					case Some(oldValue) => combiner(k)(oldValue, newValue)
 					case None => newValue
 				}
-				out += (k, v2)
+				out = out + (k, v2)
 			}
 		})
 		out
@@ -79,7 +87,7 @@ class MapK[K[_], V[_]] private[MapK](val untyped: Map[K[_], V[_]]) { self =>
 	override def toString() = {
 		val sb = new StringBuilder()
 		sb append "TypedMap {\n"
-		foreach(new FunctionK[Entry, Lambda[x => Unit]] {
+		foreach(new FunctionK[Entry, ({ type U[x] = Unit })#U] {
 			def apply[A](entry: Entry[A]): Unit = {
 				sb append "  " append entry._1.toString append ": " append entry._2.toString append "\n"
 			}
@@ -93,12 +101,14 @@ object MapK {
 
 	private[util] def tuple[K[_], V[_], T](key: K[T], value: Any): (K[T], V[T]) = (key, value.asInstanceOf[V[T]])
 
-	def coerce[K[_], V[_]](map: Map[K[_], V[_]]): MapK[K, V] = new MapK[K, V](map)
+	def coerce[K[_], V[_]](map: Map[K[Any], V[Any]]): MapK[K, V] = new MapK[K, V](map)
 
 	def empty[K[_], V[_]]: MapK[K, V] = new MapK[K, V](Map.empty)
 
-	def apply[K[_], V[_]](entries: Tuple2K[K, V, _]*): MapK[K, V] = coerce[K, V] {
-		entries.view.map { t => (t.first, t.second) }.toMap
+	def apply[K[_], V[_]](entries: Tuple2K[K, V, ?]*): MapK[K, V] = coerce[K, V] {
+		val mb = Map.newBuilder[K[Any], V[Any]]
+		for (t <- entries) mb += (t.first.asInstanceOf[K[Any]] -> t.second.asInstanceOf[V[Any]])
+		mb.result()
 	}
 
 	implicit def catsMonoidForMapK[K[_], V[_]](implicit V: SemigroupK[V]): Monoid[MapK[K, V]] = new Monoid[MapK[K, V]] {
@@ -110,4 +120,13 @@ object MapK {
 			x.merge(y, getCombiner)
 		}
 	}
+
+	/** Convenience syntax for constructing `Tuple2K` instances to use with `MapK.apply`
+	  */
+	object entrySyntax {
+		implicit class RichKey[K[_], A](key: K[A]) {
+			def ~>[V[_]](value: V[A]) = Tuple2K[K, V, A](key, value)
+			def ~>>(value: A) = Tuple2K[K, cats.Id, A](key, value)
+		}
+	}
 }

src/main/scala/com/codedx/util/MutableMapK.scala

@@ -28,24 +28,30 @@ import cats.~>
   * @tparam K
   * @tparam V
   */
-class MutableMapK[K[_], V[_]] private(private val inner: MutableMap[K[_], V[_]]) { self =>
+class MutableMapK[K[*], V[*]] private(private val inner: MutableMap[K[Any], V[Any]]) { self =>
 	def this() = this(MutableMap.empty)
 
+	override def hashCode(): Int = inner.hashCode()
+	override def equals(obj: Any): Boolean = obj match {
+		case m: MutableMapK[_, _] => m.inner == inner
+		case _ => false
+	}
+
 	type Entry[x] = (K[x], V[x])
 	def entry[T](key: K[T], value: V[T]): Entry[T] = (key, value)
 
 	override def toString = inner.toString
 
-	def contains(key: K[_]): Boolean = inner.contains(key)
-	def get[T](key: K[T]): Option[V[T]] = inner.get(key).map(_.asInstanceOf[V[T]])
-	def apply[T](key: K[T]): V[T] = inner(key).asInstanceOf[V[T]]
+	def contains[T](key: K[T]): Boolean = inner.contains(key.asInstanceOf[K[Any]])
+	def get[T](key: K[T]): Option[V[T]] = inner.get(key.asInstanceOf[K[Any]]).map(_.asInstanceOf[V[T]])
+	def apply[T](key: K[T]): V[T] = inner(key.asInstanceOf[K[Any]]).asInstanceOf[V[T]]
 	def add[T](key: K[T], value: V[T]): this.type = {
-		inner.put(key, value)
+		inner.put(key.asInstanceOf[K[Any]], value.asInstanceOf[V[Any]])
 		this
 	}
 	def add[T](entry: Entry[T]): this.type = add(entry._1, entry._2)
 	def remove[T](key: K[T]): Option[V[T]] = {
-		inner.remove(key).map(_.asInstanceOf[V[T]])
+		inner.remove(key.asInstanceOf[K[Any]]).map(_.asInstanceOf[V[T]])
 	}
 	def getOrElseUpdate[T](key: K[T], value: => V[T]) = get(key) match {
 		case None =>
@@ -57,20 +63,21 @@ class MutableMapK[K[_], V[_]] private(private val inner: MutableMap[K[_], V[_]])
 	}
 	def mapValues[U[_]](f: V ~> U) = {
 		val mapped = new MutableMapK[K, U]
-		this.foreach(new FunctionK[Entry, Lambda[x => Unit]] {
+		this.foreach(new FunctionK[Entry, ({ type U[x] = Unit })#U] {
 			def apply[A](kv: (K[A], V[A])): Unit = mapped.add(kv._1, f(kv._2))
 		})
 		mapped
 	}
 	def addFrom(that: MutableMapK[K, V]): this.type = {
-		that.foreach(new FunctionK[Entry, Lambda[x => Unit]] {
+		that.foreach(new FunctionK[Entry, ({ type U[x] = Unit })#U] {
 			def apply[A](kv: (K[A], V[A])): Unit = self.add(kv._1, kv._2)
 		})
 		this
 	}
 	def keys = inner.keySet
-	def foreach(f: Entry ~> Lambda[x => Unit]) = {
-		for ((key, value) <- inner) f(MapK.tuple(key, value))
+	def foreach(f: Entry ~> ({ type U[x] = Unit })#U) = {
+		def handleKv[A](kv: (K[Any], V[Any])) = f(MapK.tuple(kv._1.asInstanceOf[K[A]], kv._2.asInstanceOf[K[A]]))
+		for (kv <- inner) handleKv(kv)
 	}
 
 	def toMap: MapK[K, V] = MapK.coerce[K, V](inner.toMap)

src/test/scala/com/codedx/util/MapKSpec.scala

@@ -46,6 +46,34 @@ class MapKSpec extends AnyFunSpec with Matchers {
 		.updated(Name, List("a", "b"))
 
 	describe("MapK") {
+		describe("entrySyntax") {
+			import MapK.entrySyntax._
+			it ("should allow for a convenient MapK.apply with cats.Id value types") {
+				val appliedMap = MapK(Age ~>> 32, Name ~>> "Dylan", Fingers ~>> 10)
+				appliedMap shouldEqual dylan
+			}
+			it ("should allow for a convenient MapK.apply with higher-kinded value types") {
+				val appliedMap = MapK(Age ~> List(1, 2, 3, 4), Name ~> List("a", "b"))
+				appliedMap shouldEqual multi
+			}
+		}
+		
+		describe("equals and hashCode") {
+			import MapK.entrySyntax._
+			it ("should behave properly for identical MapK instances") {
+				val a = MapK(Age ~>> 21, Name ~>> "John Doe", Fingers ~>> 10)
+				val b = MapK(Age ~>> 21, Name ~>> "John Doe", Fingers ~>> 10)
+				a.equals(b) shouldBe true
+				a.hashCode shouldEqual b.hashCode
+			}
+			it ("should behave properly for non-identical MapK instances") {
+				val a = MapK(Age ~>> 21, Name ~>> "John Doe")
+				val b = MapK(Age ~>> 21, Name ~>> "John Doe", Fingers ~>> 10)
+				a.equals(b) shouldBe false
+				a.hashCode should not equal b.hashCode
+			}
+		}
+
 		describe(".untyped") {
 			it("should return a regular Map containing the same entries, minus the explicit type information") {
 				val u = ezio.untyped
@@ -139,7 +167,7 @@ class MapKSpec extends AnyFunSpec with Matchers {
 			it ("should pass each entry to the callback function, in no particular order") {
 				val seenValuesB = List.newBuilder[Any]
 				val seenKeysB = Set.newBuilder[MyKey[_]]
-				ezio.foreach(new FunctionK[ezio.Entry, Lambda[x => Unit]] {
+				ezio.foreach(new FunctionK[ezio.Entry, ({ type F[x] = Unit })#F] {
 					def apply[A](fa: (MyKey[A], Id[A])) = {
 						seenKeysB += fa._1
 						seenValuesB += fa._2
@@ -152,7 +180,9 @@ class MapKSpec extends AnyFunSpec with Matchers {
 
 		describe(".mapValues(f)") {
 			it ("should create a new MapK whose values correspond to the original map values, transformed by f") {
-				val ezioList = ezio.mapValues(Lambda[cats.Id ~> List](v => List(v, v)))
+				val ezioList = ezio.mapValues(new FunctionK[cats.Id, List] {
+					def apply[A](a: A) = List(a, a)
+				})
 				ezioList(Name) shouldEqual List("Ezio Auditore", "Ezio Auditore")
 				ezioList(Age) shouldEqual List(65, 65)
 				ezioList(Fingers) shouldEqual List(9, 9)
@@ -161,9 +191,11 @@ class MapKSpec extends AnyFunSpec with Matchers {
 
 		describe(".map(f)") {
 			it ("should create a new MapK whose entries correspond to the original map entries, transformed by f") {
-				val restoreFinger = Lambda[ezio.Entry ~> cats.Id] {
-					case (Fingers, n) => n + 1
-					case (k, v) => v
+				val restoreFinger = new FunctionK[ezio.Entry, cats.Id] {
+					def apply[A](entry: ezio.Entry[A]) = entry match {
+						case (Fingers, n) => n + 1
+						case (k, v) => v
+					}
 				}
 				val ezio2 = ezio.map(restoreFinger)
 				ezio(Fingers) shouldEqual 9
@@ -191,8 +223,8 @@ class MapKSpec extends AnyFunSpec with Matchers {
 				val max = new FunctionK[MyKey, MapK[MyKey, cats.Id]#Combiner] {
 					def apply[A](fa: MyKey[A]) = fa match {
 						case Name => (l: String, r: String) => (if (l.compareToIgnoreCase(r) > 0) l else r): String
-						case Age => _ max _
-						case Fingers => _ max _
+						case Age => (l: Int, r: Int) => l max r
+						case Fingers => (l: Int, r: Int) => l max r
 					}
 				}
 				val merged1 = ezio.merge(dylan, max)

src/test/scala/com/codedx/util/MutableMapKSpec.scala

@@ -34,6 +34,22 @@ class MutableMapKSpec extends AnyFunSpec with Matchers{
 	}
 
 	describe("MutableMapK") {
+		describe("equals and hashCode") {
+			it ("should behave properly for identical MutableMapK instances") {
+				val a = makeDemoMap
+				val b = makeDemoMap
+				a.equals(b) shouldBe true
+				a.hashCode shouldEqual b.hashCode
+			}
+			it ("should behave properly for non-identical MutableMapK instances") {
+				val a = makeDemoMap
+				val b = makeDemoMap
+				b.add(Age, 20)
+				a.equals(b) shouldBe false
+				a.hashCode should not equal b.hashCode
+			}
+		}
+
 		describe(".contains(key)") {
 			it ("should return whether or not the map contains the given key") {
 				makeDemoMap.contains(Extra) shouldBe false
@@ -112,7 +128,9 @@ class MutableMapKSpec extends AnyFunSpec with Matchers{
 
 		describe(".mapValues(f)") {
 			it ("should create a new MutableMapK whose values correspond to the original map values, transformed by f") {
-				val mapped: MutableMapK[MyKey, List] = makeDemoMap.mapValues(Lambda[cats.Id ~> List](v => List(v, v)))
+				val mapped: MutableMapK[MyKey, List] = makeDemoMap.mapValues(new FunctionK[cats.Id, List] {
+					def apply[A](v: A) = List(v, v)
+				})
 				mapped(Name) shouldEqual List("demo", "demo")
 				mapped(Age) shouldEqual List(10, 10)
 			}
@@ -154,7 +172,7 @@ class MutableMapKSpec extends AnyFunSpec with Matchers{
 				val seenValuesB = List.newBuilder[Any]
 				val seenKeysB = Set.newBuilder[MyKey[_]]
 				val m = makeDemoMap
-				m.foreach(new FunctionK[m.Entry, Lambda[x => Unit]] {
+				m.foreach(new FunctionK[m.Entry, ({ type F[x] = Unit })#F] {
 					def apply[A](fa: (MyKey[A], Id[A])) = {
 						seenKeysB += fa._1
 						seenValuesB += fa._2