Add .toOptionT (#2253)

typelevel · May 19, 2018 · 21c3039 · 21c3039
1 parent 13de346
commit 21c3039
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diff --git a/core/src/main/scala/cats/syntax/option.scala b/core/src/main/scala/cats/syntax/option.scala
@@ -1,7 +1,7 @@
 package cats
 package syntax
 
-import cats.data.{Ior, Validated, ValidatedNel}
+import cats.data.{Ior, OptionT, Validated, ValidatedNel}
 import cats.syntax.OptionOps.LiftToPartiallyApplied
 
 trait OptionSyntax {
@@ -188,6 +188,17 @@ final class OptionOps[A](val oa: Option[A]) extends AnyVal {
     */
   def liftTo[F[_]]: LiftToPartiallyApplied[F, A] = new LiftToPartiallyApplied(oa)
 
+  /**
+    * Transform the `Option` into a [[cats.data.OptionT]] while lifting it into the specified Applicative.
+    *
+    * {{{
+    * scala> import cats.implicits._
+    * scala> val op: Option[Int] = Some(3)
+    * scala> op.toOptionT[List]
+    * res0: cats.data.OptionT[List, Int] = OptionT(List(Some(3)))
+    * }}}
+    */
+  def toOptionT[F[_]: Applicative]: OptionT[F, A] = OptionT.fromOption(oa)
 }
 
 object OptionOps {

diff --git a/tests/src/test/scala/cats/tests/OptionSuite.scala b/tests/src/test/scala/cats/tests/OptionSuite.scala
@@ -94,4 +94,9 @@ class OptionSuite extends CatsSuite {
     val bomb: Eval[Option[Int]] = Later(sys.error("boom"))
     none[Int].map2Eval(bomb)(_ + _).value should === (None)
   }
+
+  test("toOptionT consistency"){
+    List(false) should === (1.some.toOptionT[List].isEmpty)
+    List(true) should === (Option.empty[Int].toOptionT[List].isEmpty)
+  }
 }