fix(ext/node): Add Immediate class to mirror NodeJS.Immediate (#22808)

Fixes #21660

Adds a basic `Immediate` class to mirror `NodeJS.Immediate`, and changes
`setImmediate` and `clearImmediate` to return and accept (respectively)
`Immediate` objects.

Note that for now {ref,unref,hasRef} are effectively stubs, as deno_core
doesn't really natively support immediates (they're currently modeled as
timers with delay of 0). Eventually we probably want to actually
implement these properly.

ext/node/polyfills/internal/timers.mjs

@@ -20,6 +20,7 @@ import { ERR_OUT_OF_RANGE } from "ext:deno_node/internal/errors.ts";
 import { emitWarning } from "node:process";
 import {
   clearTimeout as clearTimeout_,
+  setImmediate as setImmediate_,
   setInterval as setInterval_,
   setTimeout as setTimeout_,
 } from "ext:deno_web/02_timers.js";
@@ -115,6 +116,35 @@ Timeout.prototype[Symbol.toPrimitive] = function () {
   return this[kTimerId];
 };
 
+// Immediate constructor function.
+export function Immediate(callback, args) {
+  this._immediateId = setImmediate_(callback, args);
+}
+
+// Make sure the linked list only shows the minimal necessary information.
+Immediate.prototype[inspect.custom] = function (_, options) {
+  return inspect(this, {
+    ...options,
+    // Only inspect one level.
+    depth: 0,
+    // It should not recurse.
+    customInspect: false,
+  });
+};
+
+// FIXME(nathanwhit): actually implement {ref,unref,hasRef} once deno_core supports it
+Immediate.prototype.unref = function () {
+  return this;
+};
+
+Immediate.prototype.ref = function () {
+  return this;
+};
+
+Immediate.prototype.hasRef = function () {
+  return true;
+};
+
 /**
  * @param {number} msecs
  * @param {string} name

ext/node/polyfills/timers.ts

@@ -11,6 +11,7 @@ const {
 
 import {
   activeTimers,
+  Immediate,
   setUnrefTimeout,
   Timeout,
 } from "ext:deno_node/internal/timers.mjs";
@@ -21,7 +22,6 @@ import * as timers from "ext:deno_web/02_timers.js";
 
 const clearTimeout_ = timers.clearTimeout;
 const clearInterval_ = timers.clearInterval;
-const setImmediate_ = timers.setImmediate;
 
 export function setTimeout(
   callback: (...args: unknown[]) => void,
@@ -70,15 +70,21 @@ export function clearInterval(timeout?: Timeout | number | string) {
   }
   clearInterval_(id);
 }
-// TODO(bartlomieju): implement the 'NodeJS.Immediate' versions of the timers.
-// https://github.com/DefinitelyTyped/DefinitelyTyped/blob/1163ead296d84e7a3c80d71e7c81ecbd1a130e9a/types/node/v12/globals.d.ts#L1120-L1131
 export function setImmediate(
   cb: (...args: unknown[]) => void,
   ...args: unknown[]
 ): Timeout {
-  return setImmediate_(cb, ...args);
+  return new Immediate(cb, ...args);
+}
+export function clearImmediate(immediate: Immediate) {
+  if (immediate == null) {
+    return;
+  }
+
+  // FIXME(nathanwhit): will probably change once
+  //  deno_core has proper support for immediates
+  clearTimeout_(immediate._immediateId);
 }
-export const clearImmediate = clearTimeout;
 
 export default {
   setTimeout,

tests/unit_node/timers_test.ts

@@ -33,13 +33,13 @@ Deno.test("[node/timers setInterval]", () => {
 Deno.test("[node/timers setImmediate]", () => {
   {
     const { clearImmediate, setImmediate } = timers;
-    const id = setImmediate(() => {});
+    const imm = setImmediate(() => {});
-    clearImmediate(id);
+    clearImmediate(imm);
   }
 
   {
-    const id = timers.setImmediate(() => {});
+    const imm = timers.setImmediate(() => {});
-    timers.clearImmediate(id);
+    timers.clearImmediate(imm);
   }
 });
 
@@ -60,3 +60,13 @@ Deno.test("[node/timers refresh cancelled timer]", () => {
   clearTimeout(p);
   p.refresh();
 });
+
+Deno.test("[node/timers setImmediate returns Immediate object]", () => {
+  const { clearImmediate, setImmediate } = timers;
+
+  const imm = setImmediate(() => {});
+  imm.unref();
+  imm.ref();
+  imm.hasRef();
+  clearImmediate(imm);
+});