ConfDecoder: add decoding Either values

scalameta · Aug 16, 2022 · b71c0d8 · b71c0d8
1 parent 4b0d474
commit b71c0d8
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diff --git a/metaconfig-core/shared/src/main/scala/metaconfig/ConfDecoder.scala b/metaconfig-core/shared/src/main/scala/metaconfig/ConfDecoder.scala
@@ -114,6 +114,12 @@ object ConfDecoder {
         case _ => ev.read(conf).map(Some(_))
       }
 
+  implicit def canBuildEither[A, B](
+      implicit evA: ConfDecoder[A],
+      evB: ConfDecoder[B]
+  ): ConfDecoder[Either[A, B]] =
+    orElse(evA.map(x => Left(x)), evB.map(x => Right(x)))
+
   // XXX: remove this method when MIMA no longer an issue
   @deprecated("Use canBuildFromAnyMapWithStringKey instead", "0.9.2")
   implicit def canBuildFromMapWithStringKey[A](

diff --git a/metaconfig-core/shared/src/main/scala/metaconfig/ConfDecoderExT.scala b/metaconfig-core/shared/src/main/scala/metaconfig/ConfDecoderExT.scala
@@ -89,6 +89,29 @@ object ConfDecoderExT {
         case _ => ev.read(state.flatten, conf).map(Some.apply)
       }
 
+  implicit def canBuildEitherT[S, A, B](
+      implicit evA: ConfDecoderExT[S, A],
+      evB: ConfDecoderExT[S, B]
+  ): ConfDecoderExT[S, Either[A, B]] =
+    evA.map[Either[A, B]](Left.apply).orElse(evB.map[Either[A, B]](Right.apply))
+
+  implicit def canBuildEither[A, B](
+      implicit evA: ConfDecoderEx[A],
+      evB: ConfDecoderEx[B]
+  ): ConfDecoderEx[Either[A, B]] =
+    (state, conf) => {
+      @inline def asA(s: Option[A]) = evA.read(s, conf).map(x => Left(x))
+      @inline def asB(s: Option[B]) = evB.read(s, conf).map(x => Right(x))
+      state.fold {
+        asA(None).recoverWithOrCombine(asB(None))
+      } {
+        _.fold(
+          a => asA(Some(a)).recoverWithOrCombine(asB(None)),
+          b => asB(Some(b)).recoverWithOrCombine(asA(None))
+        )
+      }
+    }
+
   implicit def canBuildStringMapT[S, A, CC[_, _]](
       implicit ev: ConfDecoderExT[S, A],
       factory: Factory[(String, A), CC[String, A]],

diff --git a/metaconfig-tests/shared/src/test/scala/metaconfig/DeriveConfDecoderExSuite.scala b/metaconfig-tests/shared/src/test/scala/metaconfig/DeriveConfDecoderExSuite.scala
@@ -109,6 +109,54 @@ class DeriveConfDecoderExSuite extends munit.FunSuite {
     assert(obtained == expected)
   }
 
+  test("either") {
+    implicit val decoderOneParam: ConfDecoderEx[OneParam] =
+      generic.deriveDecoderEx[OneParam](OneParam()).noTypos
+    implicit val decoderHasOption: ConfDecoderEx[HasOption] =
+      generic.deriveDecoderEx[HasOption](HasOption()).noTypos
+    val either = implicitly[ConfDecoderEx[Either[OneParam, HasOption]]]
+    assertEquals(
+      either.read(None, Obj("param" -> Num(2))).get,
+      Left(OneParam(2))
+    )
+    assertEquals(
+      either.read(Some(Left(OneParam(1))), Obj("param" -> Num(2))).get,
+      Left(OneParam(2))
+    )
+    assertEquals(
+      either.read(Some(Right(HasOption())), Obj("param" -> Num(2))).get,
+      Left(OneParam(2))
+    )
+
+    assertEquals(
+      either.read(None, Obj("b" -> Num(2))).get,
+      Right(HasOption(Some(2)))
+    )
+    assertEquals(
+      either.read(Some(Left(OneParam(1))), Obj("b" -> Num(2))).get,
+      Right(HasOption(Some(2)))
+    )
+    assertEquals(
+      either.read(Some(Right(HasOption())), Obj("b" -> Num(2))).get,
+      Right(HasOption(Some(2)))
+    )
+
+    def getMsg(c: Configured[_]) = c.toEither.left.get.msg
+
+    assertEquals(
+      getMsg(either.read(None, Obj("c" -> Num(3)))),
+      "found option 'c' which wasn't expected, or isn't valid in this context."
+    )
+    assertEquals(
+      getMsg(either.read(Some(Left(OneParam(1))), Obj("c" -> Num(3)))),
+      "found option 'c' which wasn't expected, or isn't valid in this context."
+    )
+    assertEquals(
+      getMsg(either.read(Some(Right(HasOption())), Obj("c" -> Num(3)))),
+      "found option 'c' which wasn't expected, or isn't valid in this context."
+    )
+  }
+
   case class MissingSurface(b: Int)
 
   def checkOption(

diff --git a/metaconfig-tests/shared/src/test/scala/metaconfig/DeriveConfDecoderSuite.scala b/metaconfig-tests/shared/src/test/scala/metaconfig/DeriveConfDecoderSuite.scala
@@ -103,6 +103,26 @@ class DeriveConfDecoderSuite extends munit.FunSuite {
     assert(obtained == expected)
   }
 
+  test("either") {
+    implicit val decoderOneParam: ConfDecoder[OneParam] =
+      generic.deriveDecoder[OneParam](OneParam()).noTypos
+    implicit val decoderHasOption: ConfDecoder[HasOption] =
+      generic.deriveDecoder[HasOption](HasOption()).noTypos
+    val either = implicitly[ConfDecoder[Either[OneParam, HasOption]]]
+    assertEquals(
+      either.read(Obj("param" -> Num(2))).get,
+      Left(OneParam(2))
+    )
+    assertEquals(
+      either.read(Obj("b" -> Num(2))).get,
+      Right(HasOption(Some(2)))
+    )
+    assertEquals(
+      either.read(Obj("c" -> Num(3))).toEither.left.get.msg,
+      "found option 'c' which wasn't expected, or isn't valid in this context."
+    )
+  }
+
   case class MissingSurface(b: Int)
 
   def checkOption(conf: Conf, expected: HasOption)(