Adds Result.orThrow and Result.flatten

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Added
 * Adds `Result.catch` to enable the same behaviour as `Either.catch` (Alejandro Metke)
+* Adds `Result<Result<T>>.flatten(): Result<T>` (Jem Mawson)
 
 ### Fixed
 * `T.failure(): Result<T>` was invalid. Changed to `Throwable.failure(): Result<A>` (Jem Mawson)

lib/api/lib.api

@@ -272,7 +272,9 @@ public final class app/cash/quiver/extensions/OptionKt {
 
 public final class app/cash/quiver/extensions/ResultKt {
 	public static final fun failure (Ljava/lang/Throwable;)Ljava/lang/Object;
+	public static final fun flatten (Ljava/lang/Object;)Ljava/lang/Object;
 	public static final fun mapFailure (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;
+	public static final fun orThrow (Ljava/lang/Object;)Ljava/lang/Object;
 	public static final fun success (Ljava/lang/Object;)Ljava/lang/Object;
 	public static final fun toEither (Ljava/lang/Object;)Larrow/core/Either;
 	public static final fun toResult (Ljava/lang/Object;Lkotlin/jvm/functions/Function0;)Ljava/lang/Object;

lib/src/main/kotlin/app/cash/quiver/extensions/Result.kt

@@ -1,6 +1,9 @@
 package app.cash.quiver.extensions
 
 import arrow.core.Either
+import arrow.core.flatMap
+import arrow.core.getOrElse
+import arrow.core.identity
 import arrow.core.left
 import arrow.core.right
 
@@ -45,3 +48,13 @@ inline fun <N : Throwable, T> Result<T>.mapFailure(
 @JvmName("tryCatch")
 inline fun <R> Result.Companion.catch(f: () -> R): Result<R> =
   arrow.core.raise.catch({ success(f()) }) { failure(it) }
+
+/**
+ * Retrieves the success of a Result, or throws the failure. Alias of `getOrThrow`, included for consistency with ErrorOr.
+ */
+fun <A> Result<A>.orThrow() = getOrThrow()
+
+/**
+ * Flattens a `Result<Result<T>>` into a `Result<T>`
+ */
+fun <T> Result<Result<T>>.flatten(): Result<T> = flatMap(::identity)

lib/src/test/kotlin/app/cash/quiver/extensions/ResultTest.kt

@@ -60,4 +60,16 @@ class ResultTest : StringSpec({
       }
     }
   }
+
+  "Result.orThrow" {
+    Result.success("世界").orThrow() shouldBe "世界"
+    shouldThrow<RuntimeException> { Result.failure<Unit>(RuntimeException("thrown")).orThrow() }
+  }
+
+  "Result<Result<T>>.flatten" {
+    val exception = RuntimeException("thrown")
+    Result.success(Result.success("hello")).flatten() shouldBeSuccess "hello"
+    Result.success(Result.failure<String>(exception)).flatten() shouldBeFailure exception
+    Result.failure<Result<String>>(exception).flatten() shouldBeFailure exception
+  }
 })