Latch implements Effect<void> with .await semantics (#3638)

Co-authored-by: maksim.khramtsov <maksim.khramtsov@btsdigital.kz>

.changeset/early-poems-explode.md

@@ -0,0 +1,5 @@
+---
+"effect": minor
+---
+
+`Latch` implements `Effect<void>` with `.await` semantic

packages/effect/dtslint/Unify.ts

@@ -117,7 +117,7 @@ export type ResourceUnify = Unify.Unify<
   | Resource.Resource<any, any>
 >
 
-// $ExpectType 0 | Option<string | number> | Ref<1> | SynchronizedRef<1> | SubscriptionRef<1> | Deferred<1, 2> | Deferred<"a", "b"> | Fiber<"a" | 1, "b" | 2> | RuntimeFiber<"a" | 1, "b" | 2> | Queue<1> | Queue<"a"> | Dequeue<"a" | 1> | ScopedRef<1> | ScopedRef<"a"> | Resource<1, 2> | Ref<"A"> | SynchronizedRef<"A"> | SubscriptionRef<"A"> | FiberRef<12> | FiberRef<"a2"> | Resource<"a", never> | Either<1 | "A", 0 | "E"> | Effect<1 | "A", 0 | "E", "R" | "R1"> | RcRef<1 | "A", 0 | "E">
+// $ExpectType 0 | Option<string | number> | Ref<1> | SynchronizedRef<1> | SubscriptionRef<1> | Deferred<1, 2> | Deferred<"a", "b"> | Fiber<"a" | 1, "b" | 2> | RuntimeFiber<"a" | 1, "b" | 2> | Queue<1> | Queue<"a"> | Dequeue<"a" | 1> | ScopedRef<1> | ScopedRef<"a"> | Resource<1, 2> | Ref<"A"> | SynchronizedRef<"A"> | SubscriptionRef<"A"> | FiberRef<12> | FiberRef<"a2"> | Resource<"a", never> | Latch | Either<1 | "A", 0 | "E"> | Effect<1 | "A", 0 | "E", "R" | "R1"> | RcRef<1 | "A", 0 | "E">
 export type AllUnify = Unify.Unify<
   | Either.Either<1, 0>
   | Either.Either<"A", "E">
@@ -149,5 +149,6 @@ export type AllUnify = Unify.Unify<
   | ScopedRef.ScopedRef<"a">
   | Resource.Resource<1, 2>
   | Resource.Resource<"a">
+  | Effect.Latch
   | 0
 >

packages/effect/src/Effect.ts

@@ -5408,7 +5408,7 @@ export const makeSemaphore: (permits: number) => Effect<Semaphore> = circular.ma
  * @category latch
  * @since 3.8.0
  */
-export interface Latch {
+export interface Latch extends Effect<void> {
   /** open the latch, releasing all fibers waiting on it */
   readonly open: Effect<void>
   /** release all fibers waiting on the latch, without opening it */
@@ -5419,6 +5419,26 @@ export interface Latch {
   readonly close: Effect<void>
   /** only run the given effect when the latch is open */
   readonly whenOpen: <A, E, R>(self: Effect<A, E, R>) => Effect<A, E, R>
+
+  readonly [Unify.typeSymbol]?: unknown
+  readonly [Unify.unifySymbol]?: LatchUnify<this>
+  readonly [Unify.ignoreSymbol]?: LatchUnifyIgnore
+}
+
+/**
+ * @category models
+ * @since 3.8.0
+ */
+export interface LatchUnify<A extends { [Unify.typeSymbol]?: any }> extends EffectUnify<A> {
+  Latch?: () => Latch
+}
+
+/**
+ * @category models
+ * @since 3.8.0
+ */
+export interface LatchUnifyIgnore extends EffectUnifyIgnore {
+  Effect?: true
 }
 
 /**

packages/effect/src/internal/effect/circular.ts

@@ -112,10 +112,16 @@ export const unsafeMakeSemaphore = (permits: number): Semaphore => new Semaphore
 /** @internal */
 export const makeSemaphore = (permits: number) => core.sync(() => unsafeMakeSemaphore(permits))
 
-class Latch implements Effect.Latch {
+class Latch extends Effectable.Class<void> implements Effect.Latch {
   waiters: Array<(_: Effect.Effect<void>) => void> = []
   scheduled = false
-  constructor(private isOpen: boolean) {}
+  constructor(private isOpen: boolean) {
+    super()
+  }
+
+  commit() {
+    return this.await
+  }
 
   private unsafeSchedule(fiber: Fiber.RuntimeFiber<void>) {
     if (this.scheduled || this.waiters.length === 0) {

packages/effect/test/Effect/latch.test.ts

@@ -30,4 +30,14 @@ describe("Latch", () => {
       yield* latch.release
       assert.deepStrictEqual(yield* fiber.await, Exit.void)
     }))
+
+  it.effect("subtype of Effect", () =>
+    Effect.gen(function*() {
+      const latch = yield* Effect.makeLatch()
+      const fiber = yield* Effect.fork(latch)
+
+      yield* latch.open
+
+      assert.deepStrictEqual(yield* fiber.await, Exit.void)
+    }))
 })