Add TraverseFilter instance for Set to alleycats

typelevel · Feb 5, 2019 · 5e5147b · 5e5147b
1 parent d3b57b2
commit 5e5147b
Show file tree

Hide file tree

Showing 3 changed files with 36 additions and 11 deletions.
diff --git a/alleycats-core/src/main/scala/alleycats/std/all.scala b/alleycats-core/src/main/scala/alleycats/std/all.scala
@@ -3,12 +3,15 @@ package std
 
 import export._
 
-@reexports(
-  EmptyKInstances,
-  ListInstances,
-  OptionInstances,
-  SetInstances,
-  TryInstances,
-  IterableInstances,
-  FutureInstances
-) object all extends LegacySetInstances with LegacyTryInstances with LegacyIterableInstances with MapInstances
+@reexports(EmptyKInstances,
+           ListInstances,
+           OptionInstances,
+           SetInstances,
+           TryInstances,
+           IterableInstances,
+           FutureInstances) object all
+    extends LegacySetInstances
+    with LegacySetInstancesBinCompat0
+    with LegacyTryInstances
+    with LegacyIterableInstances
+    with MapInstances
diff --git a/alleycats-core/src/main/scala/alleycats/std/set.scala b/alleycats-core/src/main/scala/alleycats/std/set.scala
@@ -1,6 +1,6 @@
 package alleycats.std
 
-import cats.{Applicative, Eval, Foldable, Monad, Monoid, Traverse}
+import cats.{Applicative, Eval, Foldable, Monad, Monoid, Traverse, TraverseFilter}
 import export._
 
 import scala.annotation.tailrec
@@ -116,14 +116,32 @@ object SetInstances {
       override def collectFirstSome[A, B](fa: Set[A])(f: A => Option[B]): Option[B] =
         fa.collectFirst(Function.unlift(f))
     }
+
+  @export(Orphan)
+  implicit val setTraverseFilter: TraverseFilter[Set] =
+    new TraverseFilter[Set] {
+      val traverse: Traverse[Set] = setTraverse
+
+      def traverseFilter[G[_], A, B](fa: Set[A])(f: A => G[Option[B]])(implicit G: Applicative[G]): G[Set[B]] =
+        fa.foldLeft(G.pure(Set.empty[B])) { (gSet, a) =>
+          G.map2(f(a), gSet) {
+            case (Some(b), set) => set + b
+            case (None, set)    => set
+          }
+        }
+    }
 }
 
 @reexports(SetInstances)
-object set extends LegacySetInstances
+object set extends LegacySetInstances with LegacySetInstancesBinCompat0
 
 // TODO: remove when cats.{ Set, Traverse } support export-hook
 trait LegacySetInstances {
   implicit def legacySetMonad(implicit e: ExportOrphan[Monad[Set]]): Monad[Set] = e.instance
 
   implicit def legacySetTraverse(implicit e: ExportOrphan[Traverse[Set]]): Traverse[Set] = e.instance
 }
+
+trait LegacySetInstancesBinCompat0 {
+  implicit def legacySetTraverseFilter(implicit e: ExportOrphan[TraverseFilter[Set]]): TraverseFilter[Set] = e.instance
+}
diff --git a/alleycats-tests/src/test/scala/alleycats/tests/SetSuite.scala b/alleycats-tests/src/test/scala/alleycats/tests/SetSuite.scala
@@ -3,11 +3,15 @@ package alleycats.tests
 import alleycats.laws.discipline._
 import cats.Foldable
 import cats.kernel.laws.discipline.SerializableTests
+import cats.laws.discipline.arbitrary._
+import cats.laws.discipline.TraverseFilterTests
 
 import alleycats.std.all._
 
 class SetSuite extends AlleycatsSuite {
   checkAll("FlatMapRec[Set]", FlatMapRecTests[Set].tailRecM[Int])
 
   checkAll("Foldable[Set]", SerializableTests.serializable(Foldable[Set]))
+
+  checkAll("TraverseFilter[Set]", TraverseFilterTests[Set].traverseFilter[Int, Int, Int])
 }