add Mailbox module, a queue which can have done or failure signals (#3580)

Author: tim-smart

.changeset/new-dancers-ring.md

@@ -0,0 +1,6 @@
+---
+"@effect/platform": patch
+"@effect/rpc": patch
+---
+
+use Mailbox for Workers, Socket & Rpc

.changeset/thick-dingos-melt.md

@@ -0,0 +1,33 @@
+---
+"effect": minor
+---
+
+add Mailbox module, a queue which can have done or failure signals
+
+```ts
+import { Effect, Mailbox } from "effect"
+import * as assert from "node:assert"
+
+Effect.gen(function* () {
+  const mailbox = yield* Mailbox.make<number, string>()
+
+  // add messages to the mailbox
+  yield* mailbox.offer(1)
+  yield* mailbox.offer(2)
+  yield* mailbox.offerAll([3, 4, 5])
+
+  // take messages from the mailbox
+  const [messages, done] = yield* mailbox.takeAll
+  assert.deepStrictEqual(messages, [1, 2, 3, 4, 5])
+  assert.strictEqual(done, false)
+
+  // signal that the mailbox is done
+  yield* mailbox.end
+  const [messages2, done2] = yield* mailbox.takeAll
+  assert.deepStrictEqual(messages2, [])
+  assert.strictEqual(done2, true)
+
+  // signal that the mailbox is failed
+  yield* mailbox.fail("boom")
+})
+```

packages/effect/src/Mailbox.ts

@@ -0,0 +1,236 @@
+/**
+ * @since 3.8.0
+ * @experimental
+ */
+import type { Cause, NoSuchElementException } from "./Cause.js"
+import type { Channel } from "./Channel.js"
+import type { Chunk } from "./Chunk.js"
+import type { Effect } from "./Effect.js"
+import type { Exit } from "./Exit.js"
+import type { Inspectable } from "./Inspectable.js"
+import * as internal from "./internal/mailbox.js"
+import type { Option } from "./Option.js"
+import { hasProperty } from "./Predicate.js"
+import type { Stream } from "./Stream.js"
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category type ids
+ */
+export const TypeId: unique symbol = internal.TypeId
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category type ids
+ */
+export type TypeId = typeof TypeId
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category type ids
+ */
+export const ReadonlyTypeId: unique symbol = internal.ReadonlyTypeId
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category type ids
+ */
+export type ReadonlyTypeId = typeof ReadonlyTypeId
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category guards
+ */
+export const isMailbox = <A = unknown, E = unknown>(u: unknown): u is Mailbox<A, E> => hasProperty(u, TypeId)
+
+/**
+ * @since 3.8.0
+ * @experimental
+ * @category guards
+ */
+export const isReadonlyMailbox = <A = unknown, E = unknown>(u: unknown): u is ReadonlyMailbox<A, E> =>
+  hasProperty(u, ReadonlyTypeId)
+
+/**
+ * A `Mailbox` is a queue that can be signaled to be done or failed.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category models
+ */
+export interface Mailbox<in out A, in out E = never> extends ReadonlyMailbox<A, E> {
+  readonly [TypeId]: TypeId
+  /**
+   * Add a message to the mailbox. Returns `false` if the mailbox is done.
+   */
+  readonly offer: (message: A) => Effect<boolean>
+  /**
+   * Add a message to the mailbox. Returns `false` if the mailbox is done.
+   */
+  readonly unsafeOffer: (message: A) => boolean
+  /**
+   * Add multiple messages to the mailbox. Returns the remaining messages that
+   * were not added.
+   */
+  readonly offerAll: (messages: Iterable<A>) => Effect<Chunk<A>>
+  /**
+   * Add multiple messages to the mailbox. Returns the remaining messages that
+   * were not added.
+   */
+  readonly unsafeOfferAll: (messages: Iterable<A>) => Chunk<A>
+  /**
+   * Fail the mailbox with an error. If the mailbox is already done, `false` is
+   * returned.
+   */
+  readonly fail: (error: E) => Effect<boolean>
+  /**
+   * Fail the mailbox with a cause. If the mailbox is already done, `false` is
+   * returned.
+   */
+  readonly failCause: (cause: Cause<E>) => Effect<boolean>
+  /**
+   * Signal that the mailbox is complete. If the mailbox is already done, `false` is
+   * returned.
+   */
+  readonly end: Effect<boolean>
+  /**
+   * Signal that the mailbox is done. If the mailbox is already done, `false` is
+   * returned.
+   */
+  readonly done: (exit: Exit<void, E>) => Effect<boolean>
+  /**
+   * Signal that the mailbox is done. If the mailbox is already done, `false` is
+   * returned.
+   */
+  readonly unsafeDone: (exit: Exit<void, E>) => boolean
+  /**
+   * Shutdown the mailbox, canceling any pending operations.
+   * If the mailbox is already done, `false` is returned.
+   */
+  readonly shutdown: Effect<boolean>
+}
+
+/**
+ * A `ReadonlyMailbox` represents a mailbox that can only be read from.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category models
+ */
+export interface ReadonlyMailbox<out A, out E = never>
+  extends Effect<readonly [messages: Chunk<A>, done: boolean], E>, Inspectable
+{
+  readonly [ReadonlyTypeId]: ReadonlyTypeId
+  /**
+   * Take all messages from the mailbox, returning an empty Chunk if the mailbox
+   * is empty or done.
+   */
+  readonly clear: Effect<Chunk<A>, E>
+  /**
+   * Take all messages from the mailbox, or wait for messages to be available.
+   *
+   * If the mailbox is done, the `done` flag will be `true`. If the mailbox
+   * fails, the Effect will fail with the error.
+   */
+  readonly takeAll: Effect<readonly [messages: Chunk<A>, done: boolean], E>
+  /**
+   * Take a specified number of messages from the mailbox. It will only take
+   * up to the capacity of the mailbox.
+   *
+   * If the mailbox is done, the `done` flag will be `true`. If the mailbox
+   * fails, the Effect will fail with the error.
+   */
+  readonly takeN: (n: number) => Effect<readonly [messages: Chunk<A>, done: boolean], E>
+  /**
+   * Take a single message from the mailbox, or wait for a message to be
+   * available.
+   *
+   * If the mailbox is done, it will fail with `NoSuchElementException`. If the
+   * mailbox fails, the Effect will fail with the error.
+   */
+  readonly take: Effect<A, E | NoSuchElementException>
+  /** Wait for the mailbox to be done. */
+  readonly await: Effect<void, E>
+  /**
+   * Check the size of the mailbox.
+   *
+   * If the mailbox is complete, it will return `None`.
+   */
+  readonly size: Effect<Option<number>>
+  /**
+   * Check the size of the mailbox.
+   *
+   * If the mailbox is complete, it will return `None`.
+   */
+  readonly unsafeSize: () => Option<number>
+}
+
+/**
+ * A `Mailbox` is a queue that can be signaled to be done or failed.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category constructors
+ * @example
+ * import { Effect, Mailbox } from "effect"
+ *
+ * Effect.gen(function*() {
+ *   const mailbox = yield* Mailbox.make<number, string>()
+ *
+ *   // add messages to the mailbox
+ *   yield* mailbox.offer(1)
+ *   yield* mailbox.offer(2)
+ *   yield* mailbox.offerAll([3, 4, 5])
+ *
+ *   // take messages from the mailbox
+ *   const [messages, done] = yield* mailbox.takeAll
+ *   assert.deepStrictEqual(messages, [1, 2, 3, 4, 5])
+ *   assert.strictEqual(done, false)
+ *
+ *   // signal that the mailbox is done
+ *   yield* mailbox.end
+ *   const [messages2, done2] = yield* mailbox.takeAll
+ *   assert.deepStrictEqual(messages2, [])
+ *   assert.strictEqual(done2, true)
+ *
+ *   // signal that the mailbox has failed
+ *   yield* mailbox.fail("boom")
+ * })
+ */
+export const make: <A, E = never>(capacity?: number | undefined) => Effect<Mailbox<A, E>> = internal.make
+
+/**
+ * Run an `Effect` into a `Mailbox`, where success ends the mailbox and failure
+ * fails the mailbox.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category combinators
+ */
+export const into: {
+  <A, E>(self: Mailbox<A, E>): <AX, EX extends E, RX>(effect: Effect<AX, EX, RX>) => Effect<boolean, never, RX>
+  <AX, E, EX extends E, RX, A>(effect: Effect<AX, EX, RX>, self: Mailbox<A, E>): Effect<boolean, never, RX>
+} = internal.into
+
+/**
+ * Create a `Channel` from a `Mailbox`.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category conversions
+ */
+export const toChannel: <A, E>(self: ReadonlyMailbox<A, E>) => Channel<Chunk<A>, unknown, E> = internal.toChannel
+
+/**
+ * Create a `Stream` from a `Mailbox`.
+ *
+ * @since 3.8.0
+ * @experimental
+ * @category conversions
+ */
+export const toStream: <A, E>(self: ReadonlyMailbox<A, E>) => Stream<A, E> = internal.toStream

packages/effect/src/index.ts

@@ -409,6 +409,12 @@ export * as LogSpan from "./LogSpan.js"
  */
 export * as Logger from "./Logger.js"
 
+/**
+ * @since 3.8.0
+ * @experimental
+ */
+export * as Mailbox from "./Mailbox.js"
+
 /**
  * @since 2.0.0
  */

packages/effect/src/internal/core.ts

@@ -516,9 +516,7 @@ export const unsafeAsync = <A, E = never, R = never>(
     cancelerRef = register(resume)
   }
   effect.effect_instruction_i1 = blockingOn
-  return cancelerRef !== undefined ?
-    onInterrupt(effect, (_) => cancelerRef!) :
-    effect
+  return onInterrupt(effect, (_) => isEffect(cancelerRef) ? cancelerRef : void_)
 }
 
 /* @internal */