feat(async/delay): add persistent option (#2527)

_deno_unstable.ts

@@ -195,3 +195,13 @@ export function ListenerUnref(
     throw new TypeError("Requires --unstable");
   }
 }
+
+export function unrefTimer(
+  ...args: Parameters<typeof Deno.unrefTimer>
+): ReturnType<typeof Deno.unrefTimer> {
+  if (typeof Deno.unrefTimer == "function") {
+    return Deno.unrefTimer(...args);
+  } else {
+    throw new TypeError("Requires --unstable");
+  }
+}

async/README.md

@@ -135,6 +135,17 @@ const result = await delayedPromise;
 // ...
 ```
 
+To allow the process to continue to run as long as the timer exists. Requires
+`--unstable` flag.
+
+```typescript
+import { delay } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
+
+// ...
+await delay(100, { persistent: false });
+// ...
+```
+
 ## MuxAsyncIterator
 
 The MuxAsyncIterator class multiplexes multiple async iterators into a single

async/delay.ts

@@ -1,13 +1,16 @@
 // Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
 // This module is browser compatible.
+import { unrefTimer } from "../_deno_unstable.ts";
 
 export interface DelayOptions {
   signal?: AbortSignal;
+  /** Indicates whether the process should continue to run as long as the timer exists. This is `true` by default. */
+  persistent?: boolean;
 }
 
 /* Resolves after the given number of milliseconds. */
 export function delay(ms: number, options: DelayOptions = {}): Promise<void> {
-  const { signal } = options;
+  const { signal, persistent } = options;
   if (signal?.aborted) {
     return Promise.reject(new DOMException("Delay was aborted.", "AbortError"));
   }
@@ -22,5 +25,8 @@ export function delay(ms: number, options: DelayOptions = {}): Promise<void> {
     };
     const i = setTimeout(done, ms);
     signal?.addEventListener("abort", abort, { once: true });
+    if (persistent === false) {
+      unrefTimer(i);
+    }
   });
 }