add prependK/appendK for Cats NE collections

Author: satorg

core/src/main/scala-2.13+/cats/data/NonEmptyLazyList.scala

@@ -509,7 +509,7 @@ sealed abstract private[data] class NonEmptyLazyListInstances extends NonEmptyLa
 
   implicit val catsDataInstancesForNonEmptyLazyList: Bimonad[NonEmptyLazyList]
     with NonEmptyTraverse[NonEmptyLazyList]
-    with SemigroupK[NonEmptyLazyList]
+    with NonEmptyAlternative[NonEmptyLazyList]
     with Align[NonEmptyLazyList] =
     new AbstractNonEmptyInstances[LazyList, NonEmptyLazyList] with Align[NonEmptyLazyList] {
 

core/src/main/scala/cats/data/AbstractNonEmptyInstances.scala

@@ -26,17 +26,23 @@ abstract private[data] class AbstractNonEmptyInstances[F[_], NonEmptyF[_]](impli
   MF: Monad[F],
   CF: CoflatMap[F],
   TF: Traverse[F],
-  SF: SemigroupK[F]
+  SF: Alternative[F]
 ) extends Bimonad[NonEmptyF]
     with NonEmptyTraverse[NonEmptyF]
-    with SemigroupK[NonEmptyF] {
+    with NonEmptyAlternative[NonEmptyF] {
   val monadInstance = MF.asInstanceOf[Monad[NonEmptyF]]
   val coflatMapInstance = CF.asInstanceOf[CoflatMap[NonEmptyF]]
   val traverseInstance = Traverse[F].asInstanceOf[Traverse[NonEmptyF]]
-  val semiGroupKInstance = SemigroupK[F].asInstanceOf[SemigroupK[NonEmptyF]]
+  val alternativeInstance = Alternative[F].asInstanceOf[Alternative[NonEmptyF]]
 
   def combineK[A](a: NonEmptyF[A], b: NonEmptyF[A]): NonEmptyF[A] =
-    semiGroupKInstance.combineK(a, b)
+    alternativeInstance.combineK(a, b)
+
+  override def prependK[A](a: A, fa: NonEmptyF[A]): NonEmptyF[A] =
+    alternativeInstance.prependK(a, fa)
+
+  override def appendK[A](fa: NonEmptyF[A], a: A): NonEmptyF[A] =
+    alternativeInstance.appendK(fa, a)
 
   def pure[A](x: A): NonEmptyF[A] = monadInstance.pure(x)
 

core/src/main/scala/cats/data/NonEmptyChain.scala

@@ -617,10 +617,20 @@ class NonEmptyChainOps[A](private val value: NonEmptyChain[A])
 
 sealed abstract private[data] class NonEmptyChainInstances extends NonEmptyChainInstances1 {
 
-  implicit val catsDataInstancesForNonEmptyChain: SemigroupK[NonEmptyChain]
+  @deprecated(
+    "maintained for the sake of binary compatibility only, use catsDataInstancesForNonEmptyChainBinCompat1 instead",
+    "2.8.1"
+  )
+  def catsDataInstancesForNonEmptyChain: SemigroupK[NonEmptyChain]
     with NonEmptyTraverse[NonEmptyChain]
     with Bimonad[NonEmptyChain]
     with Align[NonEmptyChain] =
+    catsDataInstancesForNonEmptyChainBinCompat1
+
+  implicit val catsDataInstancesForNonEmptyChainBinCompat1: Align[NonEmptyChain]
+    with Bimonad[NonEmptyChain]
+    with NonEmptyAlternative[NonEmptyChain]
+    with NonEmptyTraverse[NonEmptyChain] =
     new AbstractNonEmptyInstances[Chain, NonEmptyChain] with Align[NonEmptyChain] {
       def extract[A](fa: NonEmptyChain[A]): A = fa.head
 

core/src/main/scala/cats/data/NonEmptyList.scala

@@ -788,23 +788,39 @@ object NonEmptyList extends NonEmptyListInstances {
 
 sealed abstract private[data] class NonEmptyListInstances extends NonEmptyListInstances0 {
 
+  @deprecated(
+    "maintained for the sake of binary compatibility only - use catsDataInstancesForNonEmptyListBinCompat1 instead",
+    "2.8.1"
+  )
+  def catsDataInstancesForNonEmptyList
+    : SemigroupK[NonEmptyList] with Bimonad[NonEmptyList] with NonEmptyTraverse[NonEmptyList] with Align[NonEmptyList] =
+    catsDataInstancesForNonEmptyListBinCompat1
+
   /**
    * This is not a bug. The declared type of `catsDataInstancesForNonEmptyList` intentionally ignores
    * `NonEmptyReducible` trait for it not being a typeclass.
    *
    * Also see the discussion: PR #3541 and issue #3069.
    */
-  implicit val catsDataInstancesForNonEmptyList
-    : SemigroupK[NonEmptyList] with Bimonad[NonEmptyList] with NonEmptyTraverse[NonEmptyList] with Align[NonEmptyList] =
+  implicit val catsDataInstancesForNonEmptyListBinCompat1: NonEmptyAlternative[NonEmptyList]
+    with Bimonad[NonEmptyList]
+    with NonEmptyTraverse[NonEmptyList]
+    with Align[NonEmptyList] =
     new NonEmptyReducible[NonEmptyList, List]
-      with SemigroupK[NonEmptyList]
+      with NonEmptyAlternative[NonEmptyList]
       with Bimonad[NonEmptyList]
       with NonEmptyTraverse[NonEmptyList]
       with Align[NonEmptyList] {
 
       def combineK[A](a: NonEmptyList[A], b: NonEmptyList[A]): NonEmptyList[A] =
         a.concatNel(b)
 
+      override def prependK[A](a: A, fa: NonEmptyList[A]): NonEmptyList[A] =
+        fa.prepend(a)
+
+      override def appendK[A](fa: NonEmptyList[A], a: A): NonEmptyList[A] =
+        fa.append(a)
+
       override def split[A](fa: NonEmptyList[A]): (A, List[A]) = (fa.head, fa.tail)
 
       override def reduceLeft[A](fa: NonEmptyList[A])(f: (A, A) => A): A =
@@ -955,7 +971,7 @@ sealed abstract private[data] class NonEmptyListInstances extends NonEmptyListIn
     new NonEmptyParallel[NonEmptyList] {
       type F[x] = ZipNonEmptyList[x]
 
-      def flatMap: FlatMap[NonEmptyList] = NonEmptyList.catsDataInstancesForNonEmptyList
+      def flatMap: FlatMap[NonEmptyList] = NonEmptyList.catsDataInstancesForNonEmptyListBinCompat1
 
       def apply: Apply[ZipNonEmptyList] = ZipNonEmptyList.catsDataCommutativeApplyForZipNonEmptyList
 

core/src/main/scala/cats/data/NonEmptySeq.scala

@@ -381,23 +381,39 @@ final class NonEmptySeq[+A] private (val toSeq: Seq[A]) extends AnyVal with NonE
 @suppressUnusedImportWarningForScalaVersionSpecific
 sealed abstract private[data] class NonEmptySeqInstances {
 
+  @deprecated(
+    "maintained for the sake of binary compatibility only - use catsDataInstancesForNonEmptySeqBinCompat1 instead",
+    "2.8.1"
+  )
+  def catsDataInstancesForNonEmptySeq
+    : SemigroupK[NonEmptySeq] with Bimonad[NonEmptySeq] with NonEmptyTraverse[NonEmptySeq] with Align[NonEmptySeq] =
+    catsDataInstancesForNonEmptySeqBinCompat1
+
   /**
    * This is not a bug. The declared type of `catsDataInstancesForNonEmptySeq` intentionally ignores
    * `NonEmptyReducible` trait for it not being a typeclass.
    *
    * Also see the discussion: PR #3541 and issue #3069.
    */
-  implicit val catsDataInstancesForNonEmptySeq
-    : SemigroupK[NonEmptySeq] with Bimonad[NonEmptySeq] with NonEmptyTraverse[NonEmptySeq] with Align[NonEmptySeq] =
+  implicit val catsDataInstancesForNonEmptySeqBinCompat1: NonEmptyAlternative[NonEmptySeq]
+    with Bimonad[NonEmptySeq]
+    with NonEmptyTraverse[NonEmptySeq]
+    with Align[NonEmptySeq] =
     new NonEmptyReducible[NonEmptySeq, Seq]
-      with SemigroupK[NonEmptySeq]
+      with NonEmptyAlternative[NonEmptySeq]
       with Bimonad[NonEmptySeq]
       with NonEmptyTraverse[NonEmptySeq]
       with Align[NonEmptySeq] {
 
       def combineK[A](a: NonEmptySeq[A], b: NonEmptySeq[A]): NonEmptySeq[A] =
         a.concatNeSeq(b)
 
+      override def prependK[A](a: A, fa: NonEmptySeq[A]): NonEmptySeq[A] =
+        fa.prepend(a)
+
+      override def appendK[A](fa: NonEmptySeq[A], a: A): NonEmptySeq[A] =
+        fa.append(a)
+
       override def split[A](fa: NonEmptySeq[A]): (A, Seq[A]) = (fa.head, fa.tail)
 
       override def size[A](fa: NonEmptySeq[A]): Long = fa.length.toLong
@@ -532,14 +548,14 @@ sealed abstract private[data] class NonEmptySeqInstances {
   implicit def catsDataShowForNonEmptySeq[A: Show]: Show[NonEmptySeq[A]] = _.show
 
   implicit def catsDataSemigroupForNonEmptySeq[A]: Semigroup[NonEmptySeq[A]] =
-    catsDataInstancesForNonEmptySeq.algebra
+    catsDataInstancesForNonEmptySeqBinCompat1.algebra
 
   implicit def catsDataParallelForNonEmptySeq: NonEmptyParallel.Aux[NonEmptySeq, ZipNonEmptySeq] =
     new NonEmptyParallel[NonEmptySeq] {
       type F[x] = ZipNonEmptySeq[x]
 
       def apply: Apply[ZipNonEmptySeq] = ZipNonEmptySeq.catsDataCommutativeApplyForZipNonEmptySeq
-      def flatMap: FlatMap[NonEmptySeq] = NonEmptySeq.catsDataInstancesForNonEmptySeq
+      def flatMap: FlatMap[NonEmptySeq] = NonEmptySeq.catsDataInstancesForNonEmptySeqBinCompat1
 
       def sequential: ZipNonEmptySeq ~> NonEmptySeq =
         new (ZipNonEmptySeq ~> NonEmptySeq) { def apply[A](a: ZipNonEmptySeq[A]): NonEmptySeq[A] = a.value }

core/src/main/scala/cats/data/NonEmptyVector.scala

@@ -386,25 +386,41 @@ final class NonEmptyVector[+A] private (val toVector: Vector[A])
 @suppressUnusedImportWarningForScalaVersionSpecific
 sealed abstract private[data] class NonEmptyVectorInstances {
 
+  @deprecated(
+    "maintained for the sake of binary compatibility only - use catsDataInstancesForNonEmptyChainBinCompat1 instead",
+    "2.8.1"
+  )
+  def catsDataInstancesForNonEmptyVector: SemigroupK[NonEmptyVector]
+    with Bimonad[NonEmptyVector]
+    with NonEmptyTraverse[NonEmptyVector]
+    with Align[NonEmptyVector] =
+    catsDataInstancesForNonEmptyVectorBinCompat1
+
   /**
    * This is not a bug. The declared type of `catsDataInstancesForNonEmptyVector` intentionally ignores
    * `NonEmptyReducible` trait for it not being a typeclass.
    *
    * Also see the discussion: PR #3541 and issue #3069.
    */
-  implicit val catsDataInstancesForNonEmptyVector: SemigroupK[NonEmptyVector]
+  implicit val catsDataInstancesForNonEmptyVectorBinCompat1: NonEmptyAlternative[NonEmptyVector]
     with Bimonad[NonEmptyVector]
     with NonEmptyTraverse[NonEmptyVector]
     with Align[NonEmptyVector] =
     new NonEmptyReducible[NonEmptyVector, Vector]
-      with SemigroupK[NonEmptyVector]
+      with NonEmptyAlternative[NonEmptyVector]
       with Bimonad[NonEmptyVector]
       with NonEmptyTraverse[NonEmptyVector]
       with Align[NonEmptyVector] {
 
       def combineK[A](a: NonEmptyVector[A], b: NonEmptyVector[A]): NonEmptyVector[A] =
         a.concatNev(b)
 
+      override def prependK[A](a: A, fa: NonEmptyVector[A]): NonEmptyVector[A] =
+        fa.prepend(a)
+
+      override def appendK[A](fa: NonEmptyVector[A], a: A): NonEmptyVector[A] =
+        fa.append(a)
+
       override def split[A](fa: NonEmptyVector[A]): (A, Vector[A]) = (fa.head, fa.tail)
 
       override def size[A](fa: NonEmptyVector[A]): Long = fa.length.toLong
@@ -550,14 +566,14 @@ sealed abstract private[data] class NonEmptyVectorInstances {
   implicit def catsDataShowForNonEmptyVector[A: Show]: Show[NonEmptyVector[A]] = _.show
 
   implicit def catsDataSemigroupForNonEmptyVector[A]: Semigroup[NonEmptyVector[A]] =
-    catsDataInstancesForNonEmptyVector.algebra
+    catsDataInstancesForNonEmptyVectorBinCompat1.algebra
 
   implicit def catsDataParallelForNonEmptyVector: NonEmptyParallel.Aux[NonEmptyVector, ZipNonEmptyVector] =
     new NonEmptyParallel[NonEmptyVector] {
       type F[x] = ZipNonEmptyVector[x]
 
       def apply: Apply[ZipNonEmptyVector] = ZipNonEmptyVector.catsDataCommutativeApplyForZipNonEmptyVector
-      def flatMap: FlatMap[NonEmptyVector] = NonEmptyVector.catsDataInstancesForNonEmptyVector
+      def flatMap: FlatMap[NonEmptyVector] = NonEmptyVector.catsDataInstancesForNonEmptyVectorBinCompat1
 
       def sequential: ZipNonEmptyVector ~> NonEmptyVector =
         new (ZipNonEmptyVector ~> NonEmptyVector) { def apply[A](a: ZipNonEmptyVector[A]): NonEmptyVector[A] = a.value }

core/src/main/scala/cats/data/OneAnd.scala

@@ -40,7 +40,7 @@ final case class OneAnd[F[_], A](head: A, tail: F[A]) {
    * Combine the head and tail into a single `F[A]` value.
    */
   def unwrap(implicit F: Alternative[F]): F[A] =
-    F.combineK(F.pure(head), tail)
+    F.prependK(head, tail)
 
   /**
    * remove elements not matching the predicate
@@ -54,7 +54,7 @@ final case class OneAnd[F[_], A](head: A, tail: F[A]) {
    * Append another OneAnd to this
    */
   def combine(other: OneAnd[F, A])(implicit F: Alternative[F]): OneAnd[F, A] =
-    OneAnd(head, F.combineK(tail, F.combineK(F.pure(other.head), other.tail)))
+    OneAnd(head, F.combineK(tail, other.unwrap))
 
   /**
    * find the first element matching the predicate, if one exists
@@ -239,7 +239,7 @@ sealed abstract private[data] class OneAndLowPriority2 extends OneAndLowPriority
       override def ap[A, B](ff: OneAnd[F, A => B])(fa: OneAnd[F, A]): OneAnd[F, B] = {
         val (f, tf) = (ff.head, ff.tail)
         val (a, ta) = (fa.head, fa.tail)
-        val fb = F.ap(tf)(F.combineK(F.pure(a), ta))
+        val fb = F.ap(tf)(F.prependK(a, ta))
         OneAnd(f(a), F.combineK(F.map(ta)(f), fb))
       }
     }

tests/shared/src/test/scala-2.13+/cats/tests/NonEmptyLazyListSuite.scala

@@ -21,24 +21,21 @@
 
 package cats.tests
 
-import cats.{Align, Bimonad, SemigroupK, Show, Traverse}
-import cats.data.{NonEmptyLazyList, NonEmptyLazyListOps, NonEmptyVector}
-import cats.kernel.{Eq, Hash, Order, PartialOrder, Semigroup}
-import cats.kernel.laws.discipline.{EqTests, HashTests, OrderTests, PartialOrderTests, SemigroupTests}
-import cats.laws.discipline.{
-  AlignTests,
-  BimonadTests,
-  NonEmptyTraverseTests,
-  SemigroupKTests,
-  SerializableTests,
-  ShortCircuitingTests
-}
+import cats._
+import cats.data.NonEmptyLazyList
+import cats.data.NonEmptyLazyListOps
+import cats.data.NonEmptyVector
+import cats.kernel.laws.discipline.EqTests
+import cats.kernel.laws.discipline.HashTests
+import cats.kernel.laws.discipline.OrderTests
+import cats.kernel.laws.discipline.PartialOrderTests
+import cats.kernel.laws.discipline.SemigroupTests
+import cats.kernel.laws.discipline.SerializableTests
+import cats.laws.discipline._
 import cats.laws.discipline.arbitrary._
 import cats.syntax.either._
-import cats.syntax.foldable._
 import cats.syntax.eq._
-import cats.Reducible
-import cats.Eval
+import cats.syntax.foldable._
 import org.scalacheck.Prop._
 
 class NonEmptyLazyListSuite extends NonEmptyCollectionSuite[LazyList, NonEmptyLazyList, NonEmptyLazyListOps] {
@@ -52,8 +49,10 @@ class NonEmptyLazyListSuite extends NonEmptyCollectionSuite[LazyList, NonEmptyLa
   checkAll(s"NonEmptyLazyList[Int]", HashTests[NonEmptyLazyList[Int]].hash)
   checkAll(s"Hash[NonEmptyLazyList[Int]]", SerializableTests.serializable(Hash[NonEmptyLazyList[Int]]))
 
-  checkAll("NonEmptyLazyList[Int]", SemigroupKTests[NonEmptyLazyList].semigroupK[Int])
-  checkAll("SemigroupK[NonEmptyLazyList]", SerializableTests.serializable(SemigroupK[NonEmptyLazyList]))
+  checkAll("NonEmptyLazyList[Int]", NonEmptyAlternativeTests[NonEmptyLazyList].nonEmptyAlternative[Int, Int, Int])
+  checkAll("NonEmptyAlternative[NonEmptyLazyList]",
+           SerializableTests.serializable(NonEmptyAlternative[NonEmptyLazyList])
+  )
 
   checkAll("NonEmptyLazyList[Int] with Option",
            NonEmptyTraverseTests[NonEmptyLazyList].nonEmptyTraverse[Option, Int, Int, Int, Int, Option, Option]

tests/shared/src/test/scala/cats/tests/NonEmptyChainSuite.scala

@@ -21,31 +21,28 @@
 
 package cats.tests
 
-import cats.{Align, Bimonad, SemigroupK, Show, Traverse}
-import cats.data.{Chain, NonEmptyChain, NonEmptyChainOps}
-import cats.kernel.{Eq, Order, PartialOrder, Semigroup}
-import cats.kernel.laws.discipline.{EqTests, OrderTests, PartialOrderTests, SemigroupTests}
-import cats.laws.discipline.{
-  AlignTests,
-  BimonadTests,
-  NonEmptyTraverseTests,
-  SemigroupKTests,
-  SerializableTests,
-  ShortCircuitingTests
-}
+import cats._
+import cats.data.Chain
+import cats.data.NonEmptyChain
+import cats.data.NonEmptyChainOps
+import cats.kernel.laws.discipline.EqTests
+import cats.kernel.laws.discipline.OrderTests
+import cats.kernel.laws.discipline.PartialOrderTests
+import cats.kernel.laws.discipline.SemigroupTests
+import cats.laws.discipline._
 import cats.laws.discipline.arbitrary._
 import cats.syntax.either._
-import cats.syntax.foldable._
 import cats.syntax.eq._
+import cats.syntax.foldable._
 import org.scalacheck.Prop._
 
 class NonEmptyChainSuite extends NonEmptyCollectionSuite[Chain, NonEmptyChain, NonEmptyChainOps] {
   protected def toList[A](value: NonEmptyChain[A]): List[A] = value.toChain.toList
   protected def underlyingToList[A](underlying: Chain[A]): List[A] = underlying.toList
   protected def toNonEmptyCollection[A](nea: NonEmptyChain[A]): NonEmptyChainOps[A] = nea
 
-  checkAll("NonEmptyChain[Int]", SemigroupKTests[NonEmptyChain].semigroupK[Int])
-  checkAll("SemigroupK[NonEmptyChain]", SerializableTests.serializable(SemigroupK[NonEmptyChain]))
+  checkAll("NonEmptyChain[Int]", NonEmptyAlternativeTests[NonEmptyChain].nonEmptyAlternative[Int, Int, Int])
+  checkAll("NonEmptyAlternative[NonEmptyChain]", SerializableTests.serializable(NonEmptyAlternative[NonEmptyChain]))
 
   checkAll("NonEmptyChain[Int] with Option",
            NonEmptyTraverseTests[NonEmptyChain].nonEmptyTraverse[Option, Int, Int, Int, Int, Option, Option]