Adds Result#handleFailureWith to easily recover from failures (#98)

block · Jul 31, 2024 · 030c57f · 030c57f
1 parent 6dc1cc9
commit 030c57f
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Showing 3 changed files with 20 additions and 1 deletion.
diff --git a/lib/api/lib.api b/lib/api/lib.api
@@ -278,6 +278,7 @@ public final class app/cash/quiver/extensions/ResultKt {
 	public static final fun failure (Ljava/lang/Throwable;)Ljava/lang/Object;
 	public static final fun flatTap (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;
 	public static final fun flatten (Ljava/lang/Object;)Ljava/lang/Object;
+	public static final fun handleFailureWith (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;
 	public static final fun isFailure (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Z
 	public static final fun isSuccess (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Z
 	public static final fun mapFailure (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;

diff --git a/lib/src/main/kotlin/app/cash/quiver/extensions/Result.kt b/lib/src/main/kotlin/app/cash/quiver/extensions/Result.kt
@@ -104,3 +104,10 @@ inline fun <T> Result<T>.isFailure(predicate: (Throwable) -> Boolean): Boolean =
  */
 inline fun <T> Result<T>.isSuccess(predicate: (T) -> Boolean): Boolean =
   fold(onFailure = { false }, onSuccess = predicate)
+
+/**
+ * Recovers errors with a function from Throwable to Result.
+ */
+inline fun <T> Result<T>.handleFailureWith(f: (Throwable) -> Result<T>): Result<T> = recoverCatching {
+  f(it).getOrThrow()
+}
diff --git a/lib/src/test/kotlin/app/cash/quiver/extensions/ResultTest.kt b/lib/src/test/kotlin/app/cash/quiver/extensions/ResultTest.kt
@@ -5,7 +5,6 @@ import app.cash.quiver.matchers.shouldBePresent
 import arrow.core.None
 import arrow.core.Some
 import arrow.core.raise.result
-import arrow.core.toOption
 import io.kotest.assertions.arrow.core.shouldBeLeft
 import io.kotest.assertions.arrow.core.shouldBeRight
 import io.kotest.assertions.throwables.shouldThrow
@@ -127,4 +126,16 @@ class ResultTest : StringSpec({
     Result.failure<String>(Exception("hello")).isSuccess { it == "hello" } shouldBe false
   }
 
+  "handleFailureWith recovers errors" {
+    1.success().handleFailureWith { Result.failure(Throwable("never happens")) }.shouldBeSuccess(1)
+    Throwable("sad panda").failure<Int>().handleFailureWith { Result.failure(Throwable("even sadder")) }
+      .shouldBeFailure().message shouldBe "even sadder"
+
+    Throwable("sad panda").failure<Int>().handleFailureWith { 1.success() }
+      .shouldBeSuccess(1)
+
+    Throwable("sad panda").failure<Int>().handleFailureWith { it.failure() }
+      .shouldBeFailure().message shouldBe "sad panda"
+  }
+
 })