scheduler 0.25.0: unstable_ImmediatePriority

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify unstable_ImmediatePriority in pkg:npm/scheduler@0.25.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/scheduler@0.25.0
Demonstrate these symbols/APIs:
  - unstable_ImmediatePriority
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:4bfbd69abb01128a28765a5f7012ff73529a1b991d52f51d7c406199a51cc4c9","constraints":{"executionContext":"node"},"contract":["scheduler.unstable_ImmediatePriority is exported as a numeric constant with value 1","unstable_ImmediatePriority has highest priority level compared to UserBlocking, Normal, Low, and Idle priorities","scheduler.unstable_runWithPriority executes callbacks with current priority set to unstable_ImmediatePriority","scheduler.unstable_scheduleCallback schedules tasks assigned with unstable_ImmediatePriority level"],"goal":"verify unstable_ImmediatePriority in pkg:npm/scheduler@0.25.0","kind":"HOW","packages":["pkg:npm/scheduler@0.25.0"],"schemaVersion":1,"symbols":["unstable_ImmediatePriority"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/scheduler@0.25.0"],"schemaVersion":1,"subject":"pkg:npm/scheduler@0.25.0","symbols":["unstable_ImmediatePriority"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-scheduler-immediate-priority",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-scheduler-immediate-priority",
      "version": "1.0.0",
      "dependencies": {
        "scheduler": "0.25.0"
      }
    },
    "node_modules/scheduler": {
      "version": "0.25.0",
      "resolved": "https://registry.npmjs.org/scheduler/-/scheduler-0.25.0.tgz",
      "integrity": "sha512-xFVuu11jh+xcO7JOAGJNOXld8/TcEHK/4CituBUeUb5hqxJLj9YuemAEuvm9gQ/+pgXYfbQuqAkiYu+u7YEsNA==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-scheduler-immediate-priority",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of scheduler unstable_ImmediatePriority",
  "main": "src/index.js",
  "dependencies": {
    "scheduler": "0.25.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify unstable_ImmediatePriority in pkg:npm/scheduler@0.25.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/scheduler@0.25.0"
  ],
  "symbols": [
    "unstable_ImmediatePriority"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const scheduler = require('scheduler');

/**
 * Returns the numeric constant representing the immediate priority level.
 * @returns {number} The immediate priority level constant.
 */
function getImmediatePriority() {
  return scheduler.unstable_ImmediatePriority;
}

/**
 * Executes a callback synchronously under the immediate priority level.
 * @param {Function} action - Function to execute under immediate priority.
 * @returns {*} The result of the action and the observed priority level.
 */
function runWithImmediatePriority(action) {
  return scheduler.unstable_runWithPriority(scheduler.unstable_ImmediatePriority, () => {
    const currentPriority = scheduler.unstable_getCurrentPriorityLevel();
    const result = action ? action() : undefined;
    return {
      priority: currentPriority,
      result
    };
  });
}

/**
 * Schedules a callback task with immediate priority level.
 * @param {Function} callback - Task callback.
 * @param {object} [options] - Scheduling options.
 * @returns {object} The scheduled task node.
 */
function scheduleImmediateTask(callback, options) {
  return scheduler.unstable_scheduleCallback(
    scheduler.unstable_ImmediatePriority,
    callback,
    options
  );
}

module.exports = {
  getImmediatePriority,
  runWithImmediatePriority,
  scheduleImmediateTask,
  scheduler
};

import assert from 'node:assert';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const {
  getImmediatePriority,
  runWithImmediatePriority,
  scheduleImmediateTask,
  scheduler
} = require('../src/index.js');

// 1. Export verification
assert.strictEqual(typeof scheduler.unstable_ImmediatePriority, 'number', 'unstable_ImmediatePriority should be exported as a number');
assert.strictEqual(scheduler.unstable_ImmediatePriority, 1, 'unstable_ImmediatePriority should equal 1');
assert.strictEqual(getImmediatePriority(), 1, 'getImmediatePriority should return 1');

// 2. Relative priority level ordering (1 is highest priority)
assert.ok(scheduler.unstable_ImmediatePriority < scheduler.unstable_UserBlockingPriority, 'Immediate priority is higher than UserBlocking');
assert.ok(scheduler.unstable_ImmediatePriority < scheduler.unstable_NormalPriority, 'Immediate priority is higher than Normal');
assert.ok(scheduler.unstable_ImmediatePriority < scheduler.unstable_LowPriority, 'Immediate priority is higher than Low');
assert.ok(scheduler.unstable_ImmediatePriority < scheduler.unstable_IdlePriority, 'Immediate priority is higher than Idle');

// 3. Execution under immediate priority with runWithImmediatePriority
const executed = runWithImmediatePriority(() => 'immediate-action-executed');
assert.strictEqual(executed.priority, scheduler.unstable_ImmediatePriority, 'Observed execution priority is unstable_ImmediatePriority');
assert.strictEqual(executed.result, 'immediate-action-executed', 'Action returns expected result under immediate priority');

// 4. Scheduling a task with unstable_ImmediatePriority
const task = scheduleImmediateTask(() => 'immediate-task-result');
assert.strictEqual(typeof task, 'object', 'scheduleImmediateTask returns a task object');
assert.strictEqual(task.priorityLevel, scheduler.unstable_ImmediatePriority, 'Task priorityLevel is unstable_ImmediatePriority');
assert.strictEqual(typeof task.callback, 'function', 'Task callback is queued');
assert.ok(typeof task.expirationTime === 'number', 'Task expirationTime is a number');

console.log('Contract assertions for unstable_ImmediatePriority passed.');