Ensure AutoCloseScope and ResourceScope only ever call finalizers once (#3530)

Author: kyay10

arrow-libs/core/arrow-autoclose/src/commonMain/kotlin/arrow/AutoCloseScope.kt

@@ -2,7 +2,6 @@ package arrow
 
 import arrow.atomic.Atomic
 import arrow.atomic.update
-import arrow.atomic.value
 import kotlin.coroutines.cancellation.CancellationException
 
 /**
@@ -97,7 +96,7 @@ internal class DefaultAutoCloseScope : AutoCloseScope {
   }
 
   fun close(error: Throwable?): Nothing? {
-    return finalizers.value.asReversed().fold(error) { acc, finalizer ->
+    return finalizers.getAndSet(emptyList()).asReversed().fold(error) { acc, finalizer ->
       acc.add(runCatching { finalizer(error) }.exceptionOrNull())
     }?.let { throw it }
   }

arrow-libs/fx/arrow-fx-coroutines/src/commonMain/kotlin/arrow/fx/coroutines/Resource.kt

@@ -3,7 +3,6 @@ package arrow.fx.coroutines
 import arrow.AutoCloseScope
 import arrow.atomic.Atomic
 import arrow.atomic.update
-import arrow.atomic.value
 import arrow.core.nonFatalOrThrow
 import arrow.core.prependTo
 import kotlinx.coroutines.CoroutineDispatcher
@@ -471,7 +470,7 @@ internal class ResourceScopeImpl : ResourceScope {
 
   suspend fun cancelAll(exitCase: ExitCase) {
     withContext(NonCancellable) {
-      finalizers.value.fold(exitCase.errorOrNull) { acc, finalizer ->
+      finalizers.getAndSet(emptyList()).fold(exitCase.errorOrNull) { acc, finalizer ->
         acc.add(runCatching { finalizer(exitCase) }.exceptionOrNull())
       }
     }?.let { throw it }

arrow-libs/fx/arrow-fx-coroutines/src/commonTest/kotlin/arrow/fx/coroutines/ResourceTest.kt

@@ -699,6 +699,21 @@ class ResourceTest {
     }
   }
 
+  @OptIn(DelicateCoroutinesApi::class)
+  @Test
+  fun allocatedRunsReleasersOnlyOnce() = runTest {
+    val released = CompletableDeferred<ExitCase>()
+    val (_, release) =
+      resource {
+        onRelease { exitCase ->
+          require(released.complete(exitCase))
+        }
+      }.allocate()
+    release(ExitCase.Completed)
+    release(ExitCase.Completed)
+    released.shouldHaveCompleted() shouldBe ExitCase.Completed
+  }
+
   private class Res : AutoCloseable {
     private val isActive = AtomicBoolean(true)