catch for EffectScope

arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/continuations/EagerEffectScope.kt

@@ -10,6 +10,8 @@ import arrow.core.identity
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
 import kotlin.coroutines.RestrictsSuspension
+import kotlin.experimental.ExperimentalTypeInference
+import kotlin.jvm.JvmInline
 
 /** Context of the [EagerEffect] DSL. */
 @RestrictsSuspension
@@ -186,6 +188,56 @@ public interface EagerEffectScope<in R> {
    */
   public suspend fun ensure(condition: Boolean, shift: () -> R): Unit =
     if (condition) Unit else shift(shift())
+
+  /**
+   * Encloses an action for which you want to catch any `shift`.
+   * [attempt] is used in combination with [catch].
+   *
+   * ```
+   * attempt { ... } catch { ... }
+   * ```
+   *
+   * The [f] may `shift` into a different `EagerEffectScope`, giving
+   * the chance for a later [catch] to change the shifted value.
+   * This is useful to simulate re-throwing of exceptions.
+   */
+  @OptIn(ExperimentalTypeInference::class)
+  public suspend fun <E, A> attempt(
+    @BuilderInference
+    f: suspend EagerEffectScope<E>.() -> A,
+  ): suspend EagerEffectScope<E>.() -> A = f
+
+
+  /**
+   * When the [EagerEffect] has shifted with [R] it will [recover]
+   * the shifted value to [A], and when it ran the computation to
+   * completion it will return the value [A].
+   * [catch] is used in combination with [attempt].
+   *
+   * ```kotlin
+   * import arrow.core.Either
+   * import arrow.core.None
+   * import arrow.core.Option
+   * import arrow.core.Validated
+   * import arrow.core.continuations.eagerEffect
+   * import io.kotest.assertions.fail
+   * import io.kotest.matchers.shouldBe
+   *
+   * fun main() {
+   *   eagerEffect<String, Int> {
+   *     val x = Either.Right(1).bind()
+   *     val y = Validated.Valid(2).bind()
+   *     val z =
+   *      attempt { None.bind { "Option was empty" } } catch { 0 }
+   *     x + y + z
+   *   }.fold({ fail("Shift can never be the result") }, { it shouldBe 3 })
+   * }
+   * ```
+   * <!--- KNIT example-eager-effect-scope-08.kt -->
+   */
+  public infix fun <E, A> (suspend EagerEffectScope<E>.() -> A).catch(
+    recover: EagerEffectScope<R>.(E) -> A,
+  ): A = eagerEffect(this).fold({ recover(it) }, ::identity)
 }
 
 /**
@@ -207,10 +259,11 @@ public interface EagerEffectScope<in R> {
  *   }.toEither() shouldBe (int?.right() ?: failure.left())
  * }
  * ```
- * <!--- KNIT example-eager-effect-scope-08.kt -->
+ * <!--- KNIT example-eager-effect-scope-09.kt -->
  */
 @OptIn(ExperimentalContracts::class)
 public suspend fun <R, B : Any> EagerEffectScope<R>.ensureNotNull(value: B?, shift: () -> R): B {
   contract { returns() implies (value != null) }
   return value ?: shift(shift())
 }
+

arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/continuations/EffectScope.kt

@@ -9,6 +9,8 @@ import arrow.core.Validated
 import arrow.core.identity
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
+import kotlin.experimental.ExperimentalTypeInference
+import kotlin.jvm.JvmInline
 
 /** Context of the [Effect] DSL. */
 public interface EffectScope<in R> {
@@ -215,6 +217,55 @@ public interface EffectScope<in R> {
    */
   public suspend fun ensure(condition: Boolean, shift: () -> R): Unit =
     if (condition) Unit else shift(shift())
+
+  /**
+   * Encloses an action for which you want to catch any `shift`.
+   * [attempt] is used in combination with [catch].
+   *
+   * ```
+   * attempt { ... } catch { ... }
+   * ```
+   *
+   * The [f] may `shift` into a different `EffectScope`, giving
+   * the chance for a later [catch] to change the shifted value.
+   * This is useful to simulate re-throwing of exceptions.
+   */
+  @OptIn(ExperimentalTypeInference::class)
+  public suspend fun <E, A> attempt(
+    @BuilderInference
+    f: suspend EffectScope<E>.() -> A,
+  ): suspend EffectScope<E>.() -> A = f
+
+  /**
+   * When the [Effect] has shifted with [R] it will [recover]
+   * the shifted value to [A], and when it ran the computation to
+   * completion it will return the value [A].
+   * [catch] is used in combination with [attempt].
+   *
+   * ```kotlin
+   * import arrow.core.Either
+   * import arrow.core.None
+   * import arrow.core.Option
+   * import arrow.core.Validated
+   * import arrow.core.continuations.effect
+   * import io.kotest.assertions.fail
+   * import io.kotest.matchers.shouldBe
+   *
+   * suspend fun main() {
+   *   effect<String, Int> {
+   *     val x = Either.Right(1).bind()
+   *     val y = Validated.Valid(2).bind()
+   *     val z =
+   *      attempt { None.bind { "Option was empty" } } catch { 0 }
+   *     x + y + z
+   *   }.fold({ fail("Shift can never be the result") }, { it shouldBe 3 })
+   * }
+   * ```
+   * <!--- KNIT example-effect-scope-09.kt -->
+   */
+  public suspend infix fun <E, A> (suspend EffectScope<E>.() -> A).catch(
+    recover: suspend EffectScope<R>.(E) -> A,
+  ): A = effect(this).fold({ recover(it) }, ::identity)
 }
 
 /**
@@ -236,10 +287,11 @@ public interface EffectScope<in R> {
  *   }.toEither() shouldBe (int?.right() ?: failure.left())
  * }
  * ```
- * <!--- KNIT example-effect-scope-09.kt -->
+ * <!--- KNIT example-effect-scope-10.kt -->
  */
 @OptIn(ExperimentalContracts::class)
 public suspend fun <R, B : Any> EffectScope<R>.ensureNotNull(value: B?, shift: () -> R): B {
   contract { returns() implies (value != null) }
   return value ?: shift(shift())
 }
+

arrow-libs/core/arrow-core/src/commonTest/kotlin/arrow/core/continuations/EffectSpec.kt

@@ -10,6 +10,7 @@ import io.kotest.matchers.shouldBe
 import io.kotest.property.Arb
 import io.kotest.property.arbitrary.boolean
 import io.kotest.property.arbitrary.int
+import io.kotest.property.arbitrary.long
 import io.kotest.property.arbitrary.orNull
 import io.kotest.property.arbitrary.string
 import io.kotest.property.checkAll
@@ -109,6 +110,32 @@ class EffectSpec :
       }
     }
 
+    "attempt - catch" {
+      checkAll(Arb.int(), Arb.long()) { i, l ->
+        effect<String, Int> {
+          attempt<Long, Int> {
+            shift(l)
+          } catch { ll ->
+            ll shouldBe l
+            i
+          }
+        }.runCont() shouldBe i
+      }
+    }
+
+    "attempt - no catch" {
+      checkAll(Arb.int(), Arb.long()) { i, l ->
+        effect<String, Int> {
+          attempt<Long, Int> {
+            i
+          } catch { ll ->
+            ll shouldBe l
+            i + 1
+          }
+        }.runCont() shouldBe i
+      }
+    }
+
     "eagerEffect can be consumed within an Effect computation" {
       checkAll(Arb.int(), Arb.int()) { a, b ->
         val eager: EagerEffect<String, Int> =

arrow-libs/core/arrow-core/src/jvmTest/kotlin/examples/example-eager-effect-scope-08.kt

@@ -1,16 +1,20 @@
 // This file was automatically generated from EagerEffectScope.kt by Knit tool. Do not edit.
 package arrow.core.examples.exampleEagerEffectScope08
 
+import arrow.core.Either
+import arrow.core.None
+import arrow.core.Option
+import arrow.core.Validated
 import arrow.core.continuations.eagerEffect
-import arrow.core.continuations.ensureNotNull
-import arrow.core.left
-import arrow.core.right
+import io.kotest.assertions.fail
 import io.kotest.matchers.shouldBe
 
 fun main() {
-  val failure = "failed"
-  val int: Int? = null
   eagerEffect<String, Int> {
-    ensureNotNull(int) { failure }
-  }.toEither() shouldBe (int?.right() ?: failure.left())
+    val x = Either.Right(1).bind()
+    val y = Validated.Valid(2).bind()
+    val z =
+     attempt { None.bind { "Option was empty" } } catch { 0 }
+    x + y + z
+  }.fold({ fail("Shift can never be the result") }, { it shouldBe 3 })
 }

arrow-libs/core/arrow-core/src/jvmTest/kotlin/examples/example-eager-effect-scope-09.kt

@@ -0,0 +1,16 @@
+// This file was automatically generated from EagerEffectScope.kt by Knit tool. Do not edit.
+package arrow.core.examples.exampleEagerEffectScope09
+
+import arrow.core.continuations.eagerEffect
+import arrow.core.continuations.ensureNotNull
+import arrow.core.left
+import arrow.core.right
+import io.kotest.matchers.shouldBe
+
+fun main() {
+  val failure = "failed"
+  val int: Int? = null
+  eagerEffect<String, Int> {
+    ensureNotNull(int) { failure }
+  }.toEither() shouldBe (int?.right() ?: failure.left())
+}

arrow-libs/core/arrow-core/src/jvmTest/kotlin/examples/example-effect-scope-09.kt

@@ -1,16 +1,20 @@
 // This file was automatically generated from EffectScope.kt by Knit tool. Do not edit.
 package arrow.core.examples.exampleEffectScope09
 
+import arrow.core.Either
+import arrow.core.None
+import arrow.core.Option
+import arrow.core.Validated
 import arrow.core.continuations.effect
-import arrow.core.continuations.ensureNotNull
-import arrow.core.left
-import arrow.core.right
+import io.kotest.assertions.fail
 import io.kotest.matchers.shouldBe
 
 suspend fun main() {
-  val failure = "failed"
-  val int: Int? = null
   effect<String, Int> {
-    ensureNotNull(int) { failure }
-  }.toEither() shouldBe (int?.right() ?: failure.left())
+    val x = Either.Right(1).bind()
+    val y = Validated.Valid(2).bind()
+    val z =
+     attempt { None.bind { "Option was empty" } } catch { 0 }
+    x + y + z
+  }.fold({ fail("Shift can never be the result") }, { it shouldBe 3 })
 }

arrow-libs/core/arrow-core/src/jvmTest/kotlin/examples/example-effect-scope-10.kt

@@ -0,0 +1,16 @@
+// This file was automatically generated from EffectScope.kt by Knit tool. Do not edit.
+package arrow.core.examples.exampleEffectScope10
+
+import arrow.core.continuations.effect
+import arrow.core.continuations.ensureNotNull
+import arrow.core.left
+import arrow.core.right
+import io.kotest.matchers.shouldBe
+
+suspend fun main() {
+  val failure = "failed"
+  val int: Int? = null
+  effect<String, Int> {
+    ensureNotNull(int) { failure }
+  }.toEither() shouldBe (int?.right() ?: failure.left())
+}