feat: add std/signal/mod.ts (#3913)

cli/js/lib.deno.ns.d.ts

@@ -2146,14 +2146,15 @@ declare namespace Deno {
    * SignalStream represents the stream of signals, implements both
    * AsyncIterator and PromiseLike
    */
-  export class SignalStream implements AsyncIterator<void>, PromiseLike<void> {
+  export class SignalStream
+    implements AsyncIterableIterator<void>, PromiseLike<void> {
     constructor(signal: typeof Deno.Signal);
     then<T, S>(
       f: (v: void) => T | Promise<T>,
       g?: (v: void) => S | Promise<S>
     ): Promise<T | S>;
     next(): Promise<IteratorResult<void>>;
-    [Symbol.asyncIterator](): AsyncIterator<void>;
+    [Symbol.asyncIterator](): AsyncIterableIterator<void>;
     dispose(): void;
   }
 

cli/js/signals.ts

@@ -96,7 +96,8 @@ export const signals = {
 
 /** SignalStream represents the stream of signals, implements both
  * AsyncIterator and PromiseLike */
-export class SignalStream implements AsyncIterator<void>, PromiseLike<void> {
+export class SignalStream
+  implements AsyncIterableIterator<void>, PromiseLike<void> {
   private rid: number;
   /** The promise of polling the signal,
    * resolves with false when it receives signal,
@@ -134,7 +135,7 @@ export class SignalStream implements AsyncIterator<void>, PromiseLike<void> {
     return { done: await this.pollingPromise, value: undefined };
   }
 
-  [Symbol.asyncIterator](): AsyncIterator<void> {
+  [Symbol.asyncIterator](): AsyncIterableIterator<void> {
     return this;
   }
 

std/signal/mod.ts

+import { MuxAsyncIterator } from "../util/async.ts";
+
+export function signal(
+  ...signos: [number, ...number[]]
+): AsyncIterable<void> & { dispose: () => void } {
+  const mux = new MuxAsyncIterator<void>();
+
+  if (signos.length < 1) {
+    throw new Error(
+      "No signals are given. You need to specify at least one signal to create a signal stream."
+    );
+  }
+
+  const streams = signos.map(Deno.signal);
+
+  streams.forEach(stream => {
+    mux.add(stream);
+  });
+
+  // Create dispose method for the muxer of signal streams.
+  const dispose = (): void => {
+    streams.forEach(stream => {
+      stream.dispose();
+    });
+  };
+
+  return Object.assign(mux, { dispose });
+}

std/signal/test.ts

+import { test, assertEquals, assertThrows } from "../testing/mod.ts";
+import { delay } from "../util/async.ts";
+import { signal } from "./mod.ts";
+
+if (Deno.build.os !== "win") {
+  test("signal() throws when called with empty signals", (): void => {
+    assertThrows(
+      () => {
+        // @ts-ignore
+        signal();
+      },
+      Error,
+      "No signals are given. You need to specify at least one signal to create a signal stream."
+    );
+  });
+
+  test("signal() iterates for multiple signals", async (): Promise<void> => {
+    // This prevents the program from exiting.
+    const t = setInterval(() => {}, 1000);
+
+    let c = 0;
+    const sig = signal(
+      Deno.Signal.SIGUSR1,
+      Deno.Signal.SIGUSR2,
+      Deno.Signal.SIGINT
+    );
+
+    setTimeout(async () => {
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGINT);
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGUSR2);
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGUSR1);
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGUSR2);
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGUSR1);
+      await delay(20);
+      Deno.kill(Deno.pid, Deno.Signal.SIGINT);
+      await delay(20);
+      sig.dispose();
+    });
+
+    for await (const _ of sig) {
+      c += 1;
+    }
+
+    assertEquals(c, 6);
+
+    clearTimeout(t);
+  });
+}