scheduler 0.25.0: unstable_LowPriority

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_LowPriority 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_LowPriority
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:sha256:7612dcd0e9bae6e61ffe56ac4c342d254860ef947f1522b204e19e531a8535ad","constraints":{"executionContext":"node"},"contract":["scheduler package.json exports valid version 0.25.0","scheduler exports unstable_LowPriority constant matching numeric priority level 4","unstable_runWithPriority executes callback with current priority set to unstable_LowPriority and restores previous priority","unstable_scheduleCallback accepts unstable_LowPriority and returns a task node with priorityLevel 4","unstable_wrapCallback preserves unstable_LowPriority execution context when invoked later"],"goal":"verify unstable_LowPriority in pkg:npm/scheduler@0.25.0","kind":"HOW","packages":["pkg:npm/scheduler@0.25.0"],"schemaVersion":1,"symbols":["unstable_LowPriority"]},"contractCommand":["node","test/contract.cjs"],"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_LowPriority"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-scheduler-unstable-low-priority",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-scheduler-unstable-low-priority",
      "version": "1.0.0",
      "license": "MIT-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-unstable-low-priority",
  "version": "1.0.0",
  "private": true,
  "license": "MIT-0",
  "dependencies": {
    "scheduler": "0.25.0"
  }
}

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

const assert = require('node:assert/strict');
const fs = require('node:fs');
const path = require('node:path');
const scheduler = require('scheduler');

// Contract 1: scheduler package.json exports valid version 0.25.0
{
  const pkgJsonPath = require.resolve('scheduler/package.json');
  assert.ok(fs.existsSync(pkgJsonPath), 'scheduler package.json should exist');
  const pkgJson = JSON.parse(fs.readFileSync(pkgJsonPath, 'utf8'));
  assert.strictEqual(pkgJson.name, 'scheduler');
  assert.strictEqual(pkgJson.version, '0.25.0');
}

// Contract 2: scheduler exports unstable_LowPriority constant matching numeric priority level 4
{
  assert.strictEqual(typeof scheduler.unstable_LowPriority, 'number');
  assert.strictEqual(scheduler.unstable_LowPriority, 4);
  assert.strictEqual(scheduler.unstable_LowPriority, 4);
  assert.ok(scheduler.unstable_LowPriority > scheduler.unstable_NormalPriority);
  assert.ok(scheduler.unstable_LowPriority < scheduler.unstable_IdlePriority);
}

// Contract 3: unstable_runWithPriority executes callback with current priority set to unstable_LowPriority and restores previous priority
{
  const initialPriority = scheduler.unstable_getCurrentPriorityLevel();
  assert.strictEqual(initialPriority, scheduler.unstable_NormalPriority);

  let observedInsidePriority = null;
  const returnValue = scheduler.unstable_runWithPriority(scheduler.unstable_LowPriority, () => {
    observedInsidePriority = scheduler.unstable_getCurrentPriorityLevel();
    return 'computed-result';
  });

  assert.strictEqual(observedInsidePriority, scheduler.unstable_LowPriority);
  assert.strictEqual(returnValue, 'computed-result');
  assert.strictEqual(scheduler.unstable_getCurrentPriorityLevel(), initialPriority);
}

// Contract 4: unstable_scheduleCallback accepts unstable_LowPriority and returns a task node with priorityLevel 4
{
  let executed = false;
  const task = scheduler.unstable_scheduleCallback(scheduler.unstable_LowPriority, () => {
    executed = true;
  });

  assert.ok(task !== null && typeof task === 'object', 'scheduleCallback should return a task object');
  assert.strictEqual(task.priorityLevel, scheduler.unstable_LowPriority);
  assert.strictEqual(task.priorityLevel, 4);
  assert.strictEqual(typeof task.expirationTime, 'number');
  assert.ok(task.expirationTime > 0);

  scheduler.unstable_cancelCallback(task);
}

// Contract 5: unstable_wrapCallback preserves unstable_LowPriority execution context when invoked later
{
  let capturedPriority = null;
  const wrappedFn = scheduler.unstable_runWithPriority(scheduler.unstable_LowPriority, () => {
    return scheduler.unstable_wrapCallback(() => {
      capturedPriority = scheduler.unstable_getCurrentPriorityLevel();
      return 'wrapped-ok';
    });
  });

  assert.strictEqual(scheduler.unstable_getCurrentPriorityLevel(), scheduler.unstable_NormalPriority);
  const result = wrappedFn();
  assert.strictEqual(result, 'wrapped-ok');
  assert.strictEqual(capturedPriority, scheduler.unstable_LowPriority);
  assert.strictEqual(scheduler.unstable_getCurrentPriorityLevel(), scheduler.unstable_NormalPriority);
}

console.log('All scheduler unstable_LowPriority contract tests passed.');