Merge pull request #2901 from armanbilge/topic/ref-access

Relax `Ref#access` semantics if set more than once
typelevel · Jun 16, 2022 · a7bb2ad · a7bb2ad
2 parents 96dca5f + 3e40f68
commit a7bb2ad
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Showing 2 changed files with 3 additions and 20 deletions.
diff --git a/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala b/kernel/shared/src/main/scala/cats/effect/kernel/Ref.scala
@@ -24,7 +24,7 @@ import cats.syntax.all._
 
 import scala.annotation.tailrec
 
-import java.util.concurrent.atomic.{AtomicBoolean, AtomicReference}
+import java.util.concurrent.atomic.AtomicReference
 
 /**
  * A thread-safe, concurrent mutable reference.
@@ -65,7 +65,7 @@ abstract class Ref[F[_], A] extends RefSource[F, A] with RefSink[F, A] {
    * (in which case `false` is returned) if another concurrent call to `access` uses its setter
    * first.
    *
-   * Once it has noop'd or been used once, a setter never succeeds again.
+   * Once it has noop'd a setter will never succeed.
    *
    * Satisfies: `r.access.map(_._1) == r.get` `r.access.flatMap { case (v, setter) =>
    * setter(f(v)) } == r.tryUpdate(f).map(_.isDefined)`
@@ -314,10 +314,7 @@ object Ref {
     def access: F[(A, A => F[Boolean])] =
       F.delay {
         val snapshot = ar.get
-        val hasBeenCalled = new AtomicBoolean(false)
-        def setter =
-          (a: A) =>
-            F.delay(hasBeenCalled.compareAndSet(false, true) && ar.compareAndSet(snapshot, a))
+        def setter = (a: A) => F.delay(ar.compareAndSet(snapshot, a))
         (snapshot, setter)
       }
 

diff --git a/tests/shared/src/test/scala/cats/effect/kernel/RefSpec.scala b/tests/shared/src/test/scala/cats/effect/kernel/RefSpec.scala
@@ -93,20 +93,6 @@ class RefSpec extends BaseSpec { outer =>
         op must completeAs(true)
     }
 
-    "access - setter should fail if called twice" in ticked { implicit ticker =>
-      val op = for {
-        r <- Ref[IO].of(0)
-        valueAndSetter <- r.access
-        (value, setter) = valueAndSetter
-        cond1 <- setter(value + 1)
-        _ <- r.set(value)
-        cond2 <- setter(value + 1)
-        result <- r.get
-      } yield cond1 && !cond2 && result == 0
-
-      op must completeAs(true)
-    }
-
     "tryUpdate - modification occurs successfully" in ticked { implicit ticker =>
       val op = for {
         r <- Ref[IO].of(0)