Add right family methods to ZPure (#375) (#443)

zio · Nov 26, 2020 · c817ec9 · c817ec9
1 parent 17ec7a0
commit c817ec9
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diff --git a/core/shared/src/main/scala/zio/prelude/fx/ZPure.scala b/core/shared/src/main/scala/zio/prelude/fx/ZPure.scala
@@ -586,6 +586,45 @@ sealed trait ZPure[-S1, +S2, -R, +E, +A] { self =>
     that: ZPure[S2, S3, R1, E1, B]
   )(f: (A, B) => C): ZPure[S1, S3, R1, E1, C] =
     self.flatMap(a => that.flatMap(b => State.succeed(f(a, b))))
+
+  /**
+   * Returns a successful computation if the value is `Right`, or fails with error `None`.
+   */
+  final def right[B, C](implicit ev: A <:< Either[B, C]): ZPure[S1, S2, R, Option[E], C] =
+    self.foldM(
+      e => ZPure.fail(Some(e)),
+      a => ev(a).fold(_ => ZPure.fail(None), ZPure.succeed)
+    )
+
+  /*
+     Returns a successful computation if the value is `Right`, or fails with error `e`.
+   */
+  final def rightOrFail[B, C, E1 >: E](e: => E1)(implicit ev: A <:< Either[B, C]): ZPure[S1, S2, R, E1, C] =
+    self.flatMap(ev(_) match {
+      case Right(value) => ZPure.succeed(value)
+      case Left(_)      => ZPure.fail(e)
+    })
+
+  /*
+     Returns a successful computation if the value is `Right`, or fails with error function `e`.
+   */
+  final def rightOrFailWith[B, C, E1 >: E](e: B => E1)(implicit ev: A <:< Either[B, C]): ZPure[S1, S2, R, E1, C] =
+    self.flatMap(ev(_) match {
+      case Right(value) => ZPure.succeed(value)
+      case Left(err)    => ZPure.fail(e(err))
+    })
+
+  /*
+     Returns a successful computation if the value is `Right`, or fails with a [[java.util.NoSuchElementException]].
+   */
+  final def rightOrFailWithException[B, C, E1 >: NoSuchElementException](implicit
+    ev: A <:< Either[B, C],
+    ev2: E <:< E1
+  ): ZPure[S1, S2, R, E1, C] =
+    self.foldM(
+      e => ZPure.fail(ev2(e)),
+      a => ev(a).fold(_ => ZPure.fail(new NoSuchElementException("Either.right.get on Left")), ZPure.succeed)
+    )
 }
 
 object ZPure {

diff --git a/core/shared/src/test/scala/zio/prelude/fx/ZPureSpec.scala b/core/shared/src/test/scala/zio/prelude/fx/ZPureSpec.scala
@@ -339,6 +339,68 @@ object ZPureSpec extends DefaultRunnableSpec {
               }
             )
           ),
+          suite("right methods")(
+            suite("right")(
+              test("failure") {
+                val result = ZPure.fail("fail").right
+                assert(result.runEither(0))(isLeft(isSome(equalTo("fail"))))
+              },
+              test("right") {
+                val result = ZPure.succeed[Int, Either[Nothing, String]](Right("Right")).right
+                assert(result.runEither(0))(isRight(equalTo((0, "Right"))))
+              },
+              test("left") {
+                val result = ZPure.succeed[Int, Either[Int, Nothing]](Left(1)).right
+                assert(result.runEither(0))(isLeft(isNone))
+              }
+            ),
+            suite("rightOrFail")(
+              test("failure") {
+                val result = ZPure.fail("fail").rightOrFail("oh crap")
+                assert(result.runEither(0))(isLeft(equalTo("fail")))
+              },
+              test("right") {
+                val result = ZPure
+                  .succeed[Int, Either[Nothing, Int]](Right(1))
+                  .rightOrFail("oh crap")
+                assert(result.runEither(0))(isRight(equalTo((0, 1))))
+              },
+              test("left") {
+                val result = ZPure.succeed[Int, Either[String, Int]](Left("Left")).rightOrFail("oh crap")
+                assert(result.runEither(0))(isLeft(equalTo("oh crap")))
+              }
+            ),
+            suite("rightOrFailWith")(
+              test("failure") {
+                val result = ZPure.fail("fail").rightOrFailWith[Any, Any, String](_ => "Oh crap")
+                assert(result.runEither(0))(isLeft(equalTo("fail")))
+              },
+              test("right") {
+                val result = ZPure
+                  .succeed[Int, Either[Nothing, Int]](Right(1))
+                  .rightOrFailWith[Any, Int, String](_ => "oh crap")
+                assert(result.runEither(0))(isRight(equalTo((0, 1))))
+              },
+              test("left") {
+                val result = ZPure.succeed[Int, Either[String, Int]](Left("Left")).rightOrFail("oh crap")
+                assert(result.runEither(0))(isLeft(equalTo("oh crap")))
+              }
+            ),
+            suite("rightOrFailWithException")(
+              test("failure") {
+                val result = ZPure.fail(new NoSuchElementException()).rightOrFailWithException
+                assert(result.runEither(0))(isLeft(isSubtype[NoSuchElementException](anything)))
+              },
+              test("right") {
+                val result = ZPure.succeed[Int, Either[Nothing, Int]](Right(1)).rightOrFailWithException
+                assert(result.runEither(0))(isRight(equalTo((0, 1))))
+              },
+              test("left") {
+                val result = ZPure.succeed[Int, Either[String, Int]](Left("Left")).rightOrFailWithException
+                assert(result.runEither(0))(isLeft(isSubtype[NoSuchElementException](anything)))
+              }
+            )
+          ),
           suite("some")(
             testM("success (Some)") {
               check(genInt, genInt, genInt) { (s1, s2, a) =>