builder-util-runtime 9.7.0: CancellationToken

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 builder-util-runtime.CancellationToken in pkg:npm/builder-util-runtime@9.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/builder-util-runtime@9.7.0
Demonstrate these symbols/APIs:
  - builder-util-runtime.CancellationToken

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.

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import { CancellationToken, CancellationError } from 'builder-util-runtime';

/**
 * Creates a new CancellationToken, optionally chained to a parent token.
 * @param {CancellationToken} [parent]
 * @returns {CancellationToken}
 */
export function createCancellationToken(parent) {
  return new CancellationToken(parent);
}

/**
 * Executes an async task with cancellation support.
 * @template T
 * @param {CancellationToken} token
 * @param {(resolve: (value: T) => void, reject: (reason?: any) => void, onCancel: (callback: () => void) => void) => void} callback
 * @returns {Promise<T>}
 */
export function executeWithCancellation(token, callback) {
  return token.createPromise(callback);
}

export { CancellationToken, CancellationError };

{
  "name": "builder-util-runtime-cancellation-token-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "builder-util-runtime-cancellation-token-sample",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "builder-util-runtime": "9.7.0"
      }
    },
    "node_modules/builder-util-runtime": {
      "version": "9.7.0",
      "resolved": "https://registry.npmjs.org/builder-util-runtime/-/builder-util-runtime-9.7.0.tgz",
      "integrity": "sha512-g/kR520giAFYkSXTzcmF3kqQq7wi8F6N6SzeDgZrqTBN+VHdmgWOyTdD1yD7AATDId/yXLvuP34CxW46/BwCdw==",
      "license": "MIT",
      "dependencies": {
        "debug": "^4.3.4",
        "sax": "^1.2.4"
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      "engines": {
        "node": ">=12.0.0"
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    "node_modules/debug": {
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      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz",
      "integrity": "sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==",
      "license": "MIT",
      "dependencies": {
        "ms": "^2.1.3"
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      "engines": {
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      "peerDependenciesMeta": {
        "supports-color": {
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      "version": "2.1.3",
      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
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      "license": "BlueOak-1.0.0",
      "engines": {
        "node": ">=11.0.0"
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}

{
  "name": "builder-util-runtime-cancellation-token-sample",
  "version": "1.0.0",
  "description": "Demonstrate builder-util-runtime.CancellationToken usage and behavior",
  "main": "index.mjs",
  "type": "module",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "builder-util-runtime": "9.7.0"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify builder-util-runtime.CancellationToken in pkg:npm/builder-util-runtime@9.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/builder-util-runtime@9.7.0"
  ],
  "symbols": [
    "builder-util-runtime.CancellationToken"
  ]
}

import assert from 'node:assert/strict';
import { EventEmitter } from 'node:events';
import { CancellationToken, CancellationError } from 'builder-util-runtime';
import { createCancellationToken, executeWithCancellation } from '../index.mjs';

// 1. assert CancellationToken starts uncancelled and emits cancel on cancel()
{
  const token = createCancellationToken();
  assert.ok(token instanceof EventEmitter, 'token must inherit from EventEmitter');
  assert.equal(token.cancelled, false, 'initial cancelled state must be false');

  let eventEmitted = false;
  token.on('cancel', () => {
    eventEmitted = true;
  });

  token.cancel();
  assert.equal(token.cancelled, true, 'cancelled state must be true after cancel()');
  assert.equal(eventEmitted, true, 'cancel event must be emitted');
}

// 2. assert child CancellationToken cancels when parent token cancels
{
  const parent = createCancellationToken();
  const child = createCancellationToken(parent);

  assert.equal(parent.cancelled, false);
  assert.equal(child.cancelled, false);

  parent.cancel();
  assert.equal(parent.cancelled, true);
  assert.equal(child.cancelled, true, 'child token must be cancelled when parent is cancelled');
}

// 3. assert createPromise resolves successfully when task completes
{
  const token = createCancellationToken();
  const result = await executeWithCancellation(token, (resolve) => {
    setTimeout(() => resolve('success-payload'), 10);
  });
  assert.equal(result, 'success-payload', 'createPromise must resolve with task value');
}

// 4. assert createPromise rejects with CancellationError and executes cleanup when cancelled
{
  const token = createCancellationToken();
  let cleanupInvoked = false;

  const promise = executeWithCancellation(token, (resolve, _reject, onCancel) => {
    const timer = setTimeout(() => resolve('done'), 1000);
    onCancel(() => {
      clearTimeout(timer);
      cleanupInvoked = true;
    });
  });

  assert.equal(token.cancelled, false);
  token.cancel();
  assert.equal(token.cancelled, true);

  await assert.rejects(
    promise,
    (err) => {
      assert.ok(err instanceof CancellationError, 'rejection error must be CancellationError');
      assert.equal(err.message, 'cancelled', 'error message must be cancelled');
      return true;
    },
    'createPromise must reject with CancellationError when cancelled'
  );
  assert.equal(cleanupInvoked, true, 'onCancel callback must be invoked');
}

// 5. assert createPromise on already-cancelled token immediately rejects with CancellationError
{
  const token = createCancellationToken();
  token.cancel();

  let taskStarted = false;
  const promise = executeWithCancellation(token, (resolve) => {
    taskStarted = true;
    resolve('done');
  });

  await assert.rejects(
    promise,
    CancellationError,
    'createPromise on cancelled token must immediately reject'
  );
  assert.equal(taskStarted, false, 'task callback must not execute when already cancelled');
}

// 6. assert dispose cleans up listeners and decouples from parent
{
  const parent = createCancellationToken();
  const child = createCancellationToken(parent);

  child.dispose();
  assert.equal(child.listenerCount('cancel'), 0, 'dispose must remove all listeners');

  parent.cancel();
  assert.equal(parent.cancelled, true);
  assert.equal(child.cancelled, false, 'disposed child must not be cancelled by parent');
}

console.log('All CancellationToken contract tests passed.');