From 475c19cbe395ad6588f1b7e103f7fc710dda576b Mon Sep 17 00:00:00 2001
From: "junie-eap[bot]" <junie-eap[bot]@users.noreply.github.com>
Date: Fri, 6 Jun 2025 10:51:07 +0000
Subject: [PATCH] feat: add getOrElseThrow method to Either type  A new method
 `getOrElseThrow` was implemented for the Arrow library's `Either` type which
 returns the right value if the Either is Right, or throws a RuntimeException
 if the Either is Left. This implementation was successfully tested and
 confirmed to work as expected. All related tasks were completed, and the
 changes were submitted without any issues.

---
 .../commonMain/kotlin/arrow/core/Either.kt    | 26 +++++++++++++++++++
 .../kotlin/arrow/core/EitherTest.kt           | 16 ++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/Either.kt b/arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/Either.kt
index 7d6f69ad694..2a8aceb7cf4 100644
--- a/arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/Either.kt
+++ b/arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/Either.kt
@@ -1368,6 +1368,32 @@ public fun <A> A.left(): Either<A, Nothing> = Left(this)
 
 public fun <A> A.right(): Either<Nothing, A> = Right(this)
 
+/**
+ * Returns the [Right] value or throws an exception created by applying the [onLeft] function to the [Left] value.
+ *
+ * ```kotlin
+ * import arrow.core.Either
+ * import io.kotest.assertions.throwables.shouldThrow
+ * import io.kotest.matchers.shouldBe
+ *
+ * fun test() {
+ *   Either.Right(12).getOrElseThrow { RuntimeException("Error: $it") } shouldBe 12
+ *   shouldThrow<RuntimeException> {
+ *     Either.Left("error").getOrElseThrow { RuntimeException("Error: $it") }
+ *   }.message shouldBe "Error: error"
+ * }
+ * ```
+ * <!--- KNIT example-either-37.kt -->
+ * <!--- TEST lines.isEmpty() -->
+ */
+public inline fun <A, B> Either<A, B>.getOrElseThrow(onLeft: (A) -> Throwable): B {
+  contract { callsInPlace(onLeft, InvocationKind.AT_MOST_ONCE) }
+  return when (this) {
+    is Left -> throw onLeft(this.value)
+    is Right -> this.value
+  }
+}
+
 public operator fun <A : Comparable<A>, B : Comparable<B>> Either<A, B>.compareTo(other: Either<A, B>): Int =
   fold(
     { a1 -> other.fold({ a2 -> a1.compareTo(a2) }, { -1 }) },
diff --git a/arrow-libs/core/arrow-core/src/commonTest/kotlin/arrow/core/EitherTest.kt b/arrow-libs/core/arrow-core/src/commonTest/kotlin/arrow/core/EitherTest.kt
index 8e570bcec97..29d139437d8 100644
--- a/arrow-libs/core/arrow-core/src/commonTest/kotlin/arrow/core/EitherTest.kt
+++ b/arrow-libs/core/arrow-core/src/commonTest/kotlin/arrow/core/EitherTest.kt
@@ -130,6 +130,22 @@ class EitherTest {
     }
   }
 
+  @Test
+  fun getOrElseThrowOk() = runTest {
+    checkAll(Arb.int(), Arb.string()) { a: Int, b: String ->
+      Right(a).getOrElseThrow { RuntimeException(it.toString()) } shouldBe a
+      
+      val exception = try {
+        Left(b).getOrElseThrow { RuntimeException(it) }
+        null // Should not reach here
+      } catch (e: RuntimeException) {
+        e
+      }
+      
+      exception?.message shouldBe b
+    }
+  }
+
   @Test
   fun getOrNullOk() = runTest {
     checkAll(Arb.int()) { a: Int ->