react-is 18.3.1: isLazy

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 react-is.isLazy in pkg:npm/react-is@18.3.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/react-is@18.3.1
Demonstrate these symbols/APIs:
  - react-is.isLazy

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:f03781d14f00450b7d939749d4fffc067318d4d8aa3b5d5e02eb170debbed82a","contract":["isLazy correctly identifies React elements created from react.lazy component types","isLazy returns false for plain React elements, component types, non-element objects, and primitives"],"goal":"verify react-is.isLazy in pkg:npm/react-is@18.3.1","kind":"HOW","packages":["pkg:npm/react-is@18.3.1"],"schemaVersion":1,"symbols":["react-is.isLazy"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/react-is@18.3.1"],"schemaVersion":1,"subject":"pkg:npm/react-is@18.3.1","symbols":["react-is.isLazy"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-react-is-lazy",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-react-is-lazy",
      "version": "1.0.0",
      "dependencies": {
        "react-is": "18.3.1"
      }
    },
    "node_modules/react-is": {
      "version": "18.3.1",
      "resolved": "https://registry.npmjs.org/react-is/-/react-is-18.3.1.tgz",
      "integrity": "sha512-/LLMVyas0ljjAtoYiPqYiL8VWXzUUdThrmU5+n20DZv+a+ClRoevUzw5JxU+Ieh5/c87ytoTBV9G1FiKfNJdmg==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-react-is-lazy",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of react-is 18.3.1 isLazy API",
  "type": "module",
  "main": "src/index.js",
  "dependencies": {
    "react-is": "18.3.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify react-is.isLazy in pkg:npm/react-is@18.3.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/react-is@18.3.1"
  ],
  "symbols": [
    "react-is.isLazy"
  ]
}

import { isLazy, Lazy } from 'react-is';

/**
 * Checks whether the given value is a React Lazy element.
 *
 * @param {*} value - The value to inspect.
 * @returns {boolean} True if the value is a React Lazy element, false otherwise.
 */
export function checkIsLazy(value) {
  return isLazy(value);
}

/**
 * Helper to create a mock React lazy element descriptor for inspection.
 *
 * @param {Function} [init] - Optional lazy initializer function.
 * @param {object} [payload] - Optional lazy payload.
 * @returns {object} A React element descriptor of lazy type.
 */
export function createLazyElement(init = () => {}, payload = {}) {
  return {
    $$typeof: Symbol.for('react.element'),
    type: {
      $$typeof: Symbol.for('react.lazy'),
      _init: init,
      _payload: payload,
    },
    props: {},
    key: null,
    ref: null,
  };
}

export { isLazy, Lazy };

import assert from 'node:assert/strict';
import { checkIsLazy, createLazyElement, isLazy, Lazy } from '../src/index.js';

// 1. Function and constant exports verification
assert.equal(typeof isLazy, 'function', 'isLazy should be a function');
assert.equal(typeof checkIsLazy, 'function', 'checkIsLazy helper should be a function');
assert.equal(typeof createLazyElement, 'function', 'createLazyElement helper should be a function');
assert.equal(typeof Lazy, 'symbol', 'Lazy should be a symbol');
assert.equal(Lazy, Symbol.for('react.lazy'), 'Lazy should match Symbol.for("react.lazy")');

// 2. isLazy correctly identifies React elements created from react.lazy component types
const lazyElement = createLazyElement();
assert.equal(isLazy(lazyElement), true, 'isLazy must return true for lazy React element');
assert.equal(checkIsLazy(lazyElement), true, 'checkIsLazy helper must return true for lazy React element');

const customLazyType = {
  $$typeof: Symbol.for('react.lazy'),
  _init: () => Promise.resolve({ default: () => null }),
  _payload: { _status: -1, _result: null },
};
const customLazyElement = {
  $$typeof: Symbol.for('react.element'),
  type: customLazyType,
  props: { id: 'lazy-test' },
  key: 'lazy-key',
  ref: null,
};
assert.equal(isLazy(customLazyElement), true, 'isLazy must return true for custom lazy element');
assert.equal(checkIsLazy(customLazyElement), true, 'checkIsLazy must return true for custom lazy element');

// 3. isLazy returns false for plain React elements, component types, non-element objects, and primitives
const plainElement = {
  $$typeof: Symbol.for('react.element'),
  type: 'div',
  props: { className: 'box' },
  key: null,
  ref: null,
};
assert.equal(isLazy(plainElement), false, 'isLazy must return false for standard HTML/DOM React element');
assert.equal(checkIsLazy(plainElement), false, 'checkIsLazy must return false for standard HTML/DOM React element');

// Component types themselves are not elements
assert.equal(isLazy(customLazyType), false, 'isLazy must return false for lazy component type descriptor itself');

// Other React element types
const fragmentElement = {
  $$typeof: Symbol.for('react.element'),
  type: Symbol.for('react.fragment'),
  props: {},
  key: null,
  ref: null,
};
assert.equal(isLazy(fragmentElement), false, 'isLazy must return false for Fragment element');

const memoElement = {
  $$typeof: Symbol.for('react.element'),
  type: { $$typeof: Symbol.for('react.memo'), type: 'span' },
  props: {},
  key: null,
  ref: null,
};
assert.equal(isLazy(memoElement), false, 'isLazy must return false for Memo element');

// Primitives and non-element objects
assert.equal(isLazy(null), false, 'isLazy must return false for null');
assert.equal(isLazy(undefined), false, 'isLazy must return false for undefined');
assert.equal(isLazy({}), false, 'isLazy must return false for empty object');
assert.equal(isLazy('react.lazy'), false, 'isLazy must return false for string');
assert.equal(isLazy(123), false, 'isLazy must return false for number');
assert.equal(isLazy(true), false, 'isLazy must return false for boolean');
assert.equal(isLazy(Symbol.for('react.lazy')), false, 'isLazy must return false for Symbol');
assert.equal(isLazy(() => {}), false, 'isLazy must return false for function');

console.log('Contract tests passed successfully.');