Merge pull request #192 from fd4s/either-codecs

Add codec support for either and subtypes
fd4s · May 12, 2020 · 44800d8 · 44800d8
2 parents 241421e + aba6aed
commit 44800d8
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diff --git a/modules/core/src/main/scala/vulcan/Codec.scala b/modules/core/src/main/scala/vulcan/Codec.scala
@@ -444,6 +444,15 @@ final object Codec {
       }
     )
 
+  /**
+    * @group General
+    */
+  implicit final def either[A, B](
+    implicit codecA: Codec[A],
+    codecB: Codec[B]
+  ): Codec[Either[A, B]] =
+    Codec.union(alt => alt[Left[A, B]] |+| alt[Right[A, B]])
+
   /**
     * Returns the result of encoding the specified value.
     *
@@ -780,6 +789,12 @@ final object Codec {
       }
     )
 
+  /**
+    * @group General
+    */
+  implicit final def left[A, B](implicit codec: Codec[A]): Codec[Left[A, B]] =
+    codec.imap(Left[A, B](_))(_.value)
+
   /**
     * @group Collection
     */
@@ -1240,6 +1255,12 @@ final object Codec {
     )
   }
 
+  /**
+    * @group General
+    */
+  implicit final def right[A, B](implicit codec: Codec[B]): Codec[Right[A, B]] =
+    codec.imap(Right[A, B](_))(_.value)
+
   /**
     * @group Collection
     */

diff --git a/modules/core/src/main/scala/vulcan/Prism.scala b/modules/core/src/main/scala/vulcan/Prism.scala
@@ -58,6 +58,15 @@ final object Prism extends PrismLowPriority {
     }
   }
 
+  /**
+    * Returns a new [[Prism]] from `Either[A, B]` to `Left[A, B]`.
+    */
+  implicit final def left[A, B]: Prism[Either[A, B], Left[A, B]] =
+    Prism.instance[Either[A, B], Left[A, B]] {
+      case left @ Left(_) => Some(left)
+      case Right(_)       => None
+    }(left => left)
+
   /**
     * Returns a new [[Prism]] from `Option` to `None`.
     */
@@ -74,6 +83,15 @@ final object Prism extends PrismLowPriority {
   final def partial[S, A](get: PartialFunction[S, A])(reverseGet: A => S): Prism[S, A] =
     Prism.instance(get.lift)(reverseGet)
 
+  /**
+    * Returns a new [[Prism]] from `Either[A, B]` to `Right[A, B]`.
+    */
+  implicit final def right[A, B]: Prism[Either[A, B], Right[A, B]] =
+    Prism.instance[Either[A, B], Right[A, B]] {
+      case Left(_)          => None
+      case right @ Right(_) => Some(right)
+    }(right => right)
+
   /**
     * Returns a new [[Prism]] from `Option` to `Some`.
     */

diff --git a/modules/core/src/test/scala/vulcan/CodecSpec.scala b/modules/core/src/test/scala/vulcan/CodecSpec.scala
@@ -512,6 +512,56 @@ final class CodecSpec extends BaseSpec {
       }
     }
 
+    describe("either") {
+      describe("schema") {
+        it("should be encoded as union") {
+          assertSchemaIs[Either[Int, Double]] {
+            """["int","double"]"""
+          }
+        }
+      }
+
+      describe("encode") {
+        it("should encode left using left schema") {
+          assertEncodeIs[Either[Int, Double]](
+            Left(1),
+            Right(1)
+          )
+        }
+
+        it("should encode right using right schema") {
+          assertEncodeIs[Either[Int, Double]](
+            Right(1d),
+            Right(1d)
+          )
+        }
+      }
+
+      describe("decode") {
+        it("should error if schema type not in union") {
+          assertDecodeError[Either[Int, Double]](
+            unsafeEncode[Either[Int, Double]](Right(1d)),
+            unsafeSchema[String],
+            "Exhausted alternatives for type java.lang.Double"
+          )
+        }
+
+        it("should decode left value as left") {
+          assertDecodeIs[Either[Int, Double]](
+            unsafeEncode[Either[Int, Double]](Left(1)),
+            Right(Left(1))
+          )
+        }
+
+        it("should decode right value as right") {
+          assertDecodeIs[Either[Int, Double]](
+            unsafeEncode[Either[Int, Double]](Right(1d)),
+            Right(Right(1d))
+          )
+        }
+      }
+    }
+
     describe("encode") {
       it("should encode using codec for type") {
         forAll { n: Int =>