Merge pull request #798 from ceedubs/streamingt-filter-bug

Fix StreamingT.filter bug
typelevel · Jan 12, 2016 · ceff342 · ceff342
2 parents ebb92ba + 815b8fb
commit ceff342
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diff --git a/core/src/main/scala/cats/data/StreamingT.scala b/core/src/main/scala/cats/data/StreamingT.scala
@@ -70,7 +70,9 @@ sealed abstract class StreamingT[F[_], A] extends Product with Serializable { lh
    */
   def filter(f: A => Boolean)(implicit ev: Functor[F]): StreamingT[F, A] =
     this match {
-      case Cons(a, ft) => if (f(a)) this else Wait(ft.map(_.filter(f)))
+      case Cons(a, ft) =>
+        val tail = ft.map(_.filter(f))
+        if (f(a)) Cons(a, tail) else Wait(tail)
       case Wait(ft) => Wait(ft.map(_.filter(f)))
       case Empty() => this
     }

diff --git a/tests/src/test/scala/cats/tests/StreamingTTests.scala b/tests/src/test/scala/cats/tests/StreamingTTests.scala
@@ -78,6 +78,11 @@ class StreamingTTests extends CatsSuite {
     }
   }
 
+  test("filter - check regression") {
+    val s = StreamingT[Option, Int](1, 2, 1)
+    s.filter(_ > 1).toList should === (Some(List(2)))
+  }
+
   test("foldLeft with Id consistent with List.foldLeft") {
     forAll { (s: StreamingT[Id, Int], l: Long, f: (Long, Int) => Long) =>
       s.foldLeft(l)(f) should === (s.toList.foldLeft(l)(f))