react-is 19.2.8: isProfiler

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.isProfiler in pkg:npm/react-is@19.2.8
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/react-is@19.2.8
Demonstrate these symbols/APIs:
  - react-is.isProfiler

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:e4eabbc8cb56064608329b94a9fb1da75a7476bb670a42104d29bac9149bf268","contract":["isProfiler identifies React Profiler elements created with Element and Profiler symbols","isProfiler rejects plain elements, fragments, primitives, null, and non-element objects","isProfiler rejects elements using legacy React 18 element symbols","isValidElementType validates Profiler symbol as an acceptable element type","typeOf returns Profiler symbol for Profiler elements"],"goal":"verify react-is.isProfiler in pkg:npm/react-is@19.2.8","kind":"HOW","packages":["pkg:npm/react-is@19.2.8"],"schemaVersion":1,"symbols":["react-is.isProfiler"]},"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@19.2.8"],"schemaVersion":1,"subject":"pkg:npm/react-is@19.2.8","symbols":["react-is.isProfiler"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-react-is-profiler",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-react-is-profiler",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "react-is": "19.2.8"
      }
    },
    "node_modules/react-is": {
      "version": "19.2.8",
      "resolved": "https://registry.npmjs.org/react-is/-/react-is-19.2.8.tgz",
      "integrity": "sha512-s5un28nYxKJw5gvUHyW5PCC28CvBqLu9r3cWgzHT4Vo/5fqqkFcdRYsGcKf50WMPpjjFZS5d76fn3YCo2njKwQ==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-react-is-profiler",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of react-is 19.2.8 isProfiler API",
  "type": "module",
  "main": "src/index.js",
  "dependencies": {
    "react-is": "19.2.8"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify react-is.isProfiler in pkg:npm/react-is@19.2.8",
  "kind": "HOW",
  "packages": [
    "pkg:npm/react-is@19.2.8"
  ],
  "symbols": [
    "react-is.isProfiler"
  ]
}

import {
  isProfiler,
  Profiler,
  Element,
  typeOf,
  isValidElementType,
} from 'react-is';

/**
 * Check if the given value is a React Profiler element.
 *
 * @param {*} value - The value to check.
 * @returns {boolean} True if the value is a Profiler element.
 */
export function checkIsProfiler(value) {
  return isProfiler(value);
}

/**
 * Check if the given type is a valid React element type.
 *
 * @param {*} value - The type to check.
 * @returns {boolean} True if the type is a valid element type.
 */
export function checkIsValidElementType(value) {
  return isValidElementType(value);
}

/**
 * Identify the React element type symbol of a given object.
 *
 * @param {*} value - The React element to inspect.
 * @returns {symbol|undefined} The matched React symbol or undefined.
 */
export function identifyTypeOf(value) {
  return typeOf(value);
}

export {
  isProfiler,
  Profiler,
  Element,
  typeOf,
  isValidElementType,
};

import assert from 'node:assert/strict';
import {
  checkIsProfiler,
  checkIsValidElementType,
  identifyTypeOf,
  isProfiler,
  isValidElementType,
  typeOf,
  Profiler,
  Element,
} from '../src/index.js';

// 1. Export verification
assert.equal(typeof isProfiler, 'function', 'isProfiler should be a function');
assert.equal(typeof checkIsProfiler, 'function', 'checkIsProfiler should be a function');
assert.equal(typeof checkIsValidElementType, 'function', 'checkIsValidElementType should be a function');
assert.equal(typeof identifyTypeOf, 'function', 'identifyTypeOf should be a function');
assert.equal(typeof Profiler, 'symbol', 'Profiler should be a symbol');
assert.equal(typeof Element, 'symbol', 'Element should be a symbol');
assert.equal(Profiler, Symbol.for('react.profiler'), 'Profiler should match Symbol.for("react.profiler")');
assert.equal(Element, Symbol.for('react.transitional.element'), 'Element should match Symbol.for("react.transitional.element")');

// 2. Profiler element detection with React 19 transitional element
const validProfilerElement = {
  $$typeof: Element,
  type: Profiler,
  props: { id: 'test-profiler', onRender: () => {} },
  key: null,
  ref: null,
};

assert.equal(isProfiler(validProfilerElement), true, 'Valid Profiler element must be detected by isProfiler');
assert.equal(checkIsProfiler(validProfilerElement), true, 'checkIsProfiler helper must return true for valid Profiler element');
assert.equal(typeOf(validProfilerElement), Profiler, 'typeOf must return Profiler symbol for Profiler element');
assert.equal(identifyTypeOf(validProfilerElement), Profiler, 'identifyTypeOf helper must return Profiler symbol');

// 3. Profiler rejects plain element and non-Profiler element types
const plainElement = {
  $$typeof: Element,
  type: 'div',
  props: {},
  key: null,
  ref: null,
};
assert.equal(isProfiler(plainElement), false, 'Plain element must not be detected as Profiler');

const fragmentElement = {
  $$typeof: Element,
  type: Symbol.for('react.fragment'),
  props: {},
  key: null,
  ref: null,
};
assert.equal(isProfiler(fragmentElement), false, 'Fragment element must not be detected as Profiler');

// 4. Profiler rejects primitives, null, undefined, and non-element objects
assert.equal(isProfiler(null), false, 'null is not a Profiler');
assert.equal(isProfiler(undefined), false, 'undefined is not a Profiler');
assert.equal(isProfiler({}), false, 'Empty object is not a Profiler');
assert.equal(isProfiler('profiler'), false, 'String is not a Profiler');
assert.equal(isProfiler(123), false, 'Number is not a Profiler');
assert.equal(isProfiler(Profiler), false, 'Symbol itself is not a Profiler element');

// 5. Profiler rejects legacy React 18/17 element representations
const legacyElement = {
  $$typeof: Symbol.for('react.element'),
  type: Profiler,
  props: {},
  key: null,
  ref: null,
};
assert.equal(isProfiler(legacyElement), false, 'Legacy react.element representation is rejected in React 19');

// 6. Element type validation
assert.equal(isValidElementType(Profiler), true, 'Profiler symbol is a valid element type');
assert.equal(checkIsValidElementType(Profiler), true, 'checkIsValidElementType returns true for Profiler');

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