pretty-format 29.7.0: plugins

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 plugins in pkg:npm/pretty-format@29.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/pretty-format@29.7.0
Demonstrate these symbols/APIs:
  - plugins

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:sha256:16e7c8d985b2c94cc4e1d300cb4be56fb96479cabd90f0c8a04073ed4f0a28bb","contract":["plugins exports built-in serializer plugins including ReactElement, ReactTestComponent, and AsymmetricMatcher","format with plugins.ReactElement formats React element structures into JSX-like strings","format with plugins.ReactTestComponent formats React test renderer JSON structures","format with plugins.AsymmetricMatcher formats Jest asymmetric matchers","format supports custom plugins implementing test and serialize hooks","format supports recursive nested serialization with printer in custom plugins","format applies plugins in array order where earlier matching plugins take precedence","format ignores plugins when test returns false and falls back to default formatting"],"goal":"verify plugins in pkg:npm/pretty-format@29.7.0","kind":"HOW","packages":["pkg:npm/pretty-format@29.7.0"],"schemaVersion":1,"symbols":["plugins"]},"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/pretty-format@29.7.0"],"schemaVersion":1,"subject":"pkg:npm/pretty-format@29.7.0","symbols":["plugins"],"verifierAdapter":"node-typescript@1"}

import prettyFormat, { format, plugins, DEFAULT_OPTIONS } from 'pretty-format';

export { prettyFormat, format, plugins, DEFAULT_OPTIONS };

/**
 * Format a value using provided plugins array.
 */
export function formatWithPlugins(value, pluginList, options = {}) {
  return format(value, { ...options, plugins: pluginList });
}

/**
 * Format a value using a custom test/serialize plugin.
 */
export function formatWithCustomSerializer(value, testFn, serializeFn, options = {}) {
  const plugin = {
    test: testFn,
    serialize: serializeFn,
  };
  return format(value, { ...options, plugins: [plugin] });
}

/**
 * Create a simple custom serializer plugin.
 */
export function createCustomPlugin(testFn, serializeFn) {
  return {
    test: testFn,
    serialize: serializeFn,
  };
}

{
  "name": "sample-pretty-format-plugins",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-pretty-format-plugins",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "pretty-format": "29.7.0"
      }
    },
    "node_modules/@jest/schemas": {
      "version": "29.6.3",
      "resolved": "https://registry.npmjs.org/@jest/schemas/-/schemas-29.6.3.tgz",
      "integrity": "sha512-mo5j5X+jIZmJQveBKeS/clAueipV7KgiX1vMgCxam1RNYiqE1w62n0/tJJnHtjW8ZHcQco5gY85jA3mi0L+nSA==",
      "license": "MIT",
      "dependencies": {
        "@sinclair/typebox": "^0.27.8"
      },
      "engines": {
        "node": "^14.15.0 || ^16.10.0 || >=18.0.0"
      }
    },
    "node_modules/@sinclair/typebox": {
      "version": "0.27.12",
      "resolved": "https://registry.npmjs.org/@sinclair/typebox/-/typebox-0.27.12.tgz",
      "integrity": "sha512-hhyNJ+nbR6ZR7pToHvllEFun9TL0sbL+tk/ON75lo+Xas054uez98qRbsuNt7MBCyZKK4+8Yli/OAGZhmfBZ/g==",
      "license": "MIT"
    },
    "node_modules/ansi-styles": {
      "version": "5.2.0",
      "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-5.2.0.tgz",
      "integrity": "sha512-Cxwpt2SfTzTtXcfOlzGEee8O+c+MmUgGrNiBcXnuWxuFJHe6a5Hz7qwhwe5OgaSYI0IJvkLqWX1ASG+cJOkEiA==",
      "license": "MIT",
      "engines": {
        "node": ">=10"
      },
      "funding": {
        "url": "https://github.com/chalk/ansi-styles?sponsor=1"
      }
    },
    "node_modules/pretty-format": {
      "version": "29.7.0",
      "resolved": "https://registry.npmjs.org/pretty-format/-/pretty-format-29.7.0.tgz",
      "integrity": "sha512-Pdlw/oPxN+aXdmM9R00JVC9WVFoCLTKJvDVLgmJ+qAffBMxsV85l/Lu7sNx4zSzPyoL2euImuEwHhOXdEgNFZQ==",
      "license": "MIT",
      "dependencies": {
        "@jest/schemas": "^29.6.3",
        "ansi-styles": "^5.0.0",
        "react-is": "^18.0.0"
      },
      "engines": {
        "node": "^14.15.0 || ^16.10.0 || >=18.0.0"
      }
    },
    "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-pretty-format-plugins",
  "version": "1.0.0",
  "description": "Clean-room verification sample for pretty-format plugins",
  "type": "module",
  "main": "index.mjs",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "pretty-format": "29.7.0"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify plugins in pkg:npm/pretty-format@29.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/pretty-format@29.7.0"
  ],
  "symbols": [
    "plugins"
  ]
}

import assert from 'node:assert/strict';
import prettyFormat, { format, plugins, DEFAULT_OPTIONS } from 'pretty-format';
import {
  formatWithPlugins,
  formatWithCustomSerializer,
  createCustomPlugin,
} from '../index.mjs';

// 1. plugins exports built-in serializer plugins including ReactElement, ReactTestComponent, and AsymmetricMatcher
{
  assert.equal(typeof plugins, 'object');
  assert.equal(typeof plugins.ReactElement.test, 'function');
  assert.equal(typeof plugins.ReactElement.serialize, 'function');
  assert.equal(typeof plugins.ReactTestComponent.test, 'function');
  assert.equal(typeof plugins.ReactTestComponent.serialize, 'function');
  assert.equal(typeof plugins.AsymmetricMatcher.test, 'function');
  assert.equal(typeof plugins.AsymmetricMatcher.serialize, 'function');
  assert.equal(typeof plugins.DOMElement.test, 'function');
  assert.equal(typeof plugins.DOMCollection.test, 'function');
  assert.equal(typeof plugins.Immutable.test, 'function');
}

// 2. format with plugins.ReactElement formats React element structures into JSX-like strings
{
  const reactEl = {
    $$typeof: Symbol.for('react.element'),
    type: 'div',
    props: { className: 'card' },
    key: null,
    ref: null,
  };
  const result = format(reactEl, { plugins: [plugins.ReactElement] });
  assert.equal(result, '<div\n  className="card"\n/>');
  assert.equal(formatWithPlugins(reactEl, [plugins.ReactElement]), '<div\n  className="card"\n/>');
}

// 3. format with plugins.ReactTestComponent formats React test renderer JSON structures
{
  const testComp = {
    $$typeof: Symbol.for('react.test.json'),
    type: 'button',
    props: { disabled: true },
    children: ['Click'],
  };
  const result = format(testComp, { plugins: [plugins.ReactTestComponent] });
  assert.equal(result, '<button\n  disabled={true}\n>\n  Click\n</button>');
}

// 4. format with plugins.AsymmetricMatcher formats Jest asymmetric matchers
{
  const matcher = {
    $$typeof: Symbol.for('jest.asymmetricMatcher'),
    asymmetricMatch: () => true,
    toAsymmetricMatcher: () => 'StringMatching(/xyz/)',
  };
  const result = format(matcher, { plugins: [plugins.AsymmetricMatcher] });
  assert.equal(result, 'StringMatching(/xyz/)');
}

// 5. format supports custom plugins implementing test and serialize hooks
{
  const personPlugin = createCustomPlugin(
    (val) => val && val.__type === 'Person',
    (val) => `Person(${val.name}, ${val.age})`
  );
  const data = { user: { __type: 'Person', name: 'Bob', age: 25 } };
  const result = format(data, { plugins: [personPlugin] });
  assert.equal(result, 'Object {\n  "user": Person(Bob, 25),\n}');

  const helperResult = formatWithCustomSerializer(
    data,
    (val) => val && val.__type === 'Person',
    (val) => `Person(${val.name}, ${val.age})`
  );
  assert.equal(helperResult, 'Object {\n  "user": Person(Bob, 25),\n}');
}

// 6. format supports recursive nested serialization with printer in custom plugins
{
  const wrapperPlugin = {
    test: (val) => val && val.__type === 'Wrapper',
    serialize: (val, config, indentation, depth, refs, printer) => {
      return `Wrapper<${printer(val.inner, config, indentation, depth, refs)}>`;
    },
  };
  const wrapped = { __type: 'Wrapper', inner: 42 };
  assert.equal(format(wrapped, { plugins: [wrapperPlugin] }), 'Wrapper<42>');
}

// 7. format applies plugins in array order where earlier matching plugins take precedence
{
  const pluginA = {
    test: (val) => val && val.tag === 'special',
    serialize: () => 'PluginA',
  };
  const pluginB = {
    test: (val) => val && val.tag === 'special',
    serialize: () => 'PluginB',
  };
  assert.equal(format({ tag: 'special' }, { plugins: [pluginA, pluginB] }), 'PluginA');
  assert.equal(format({ tag: 'special' }, { plugins: [pluginB, pluginA] }), 'PluginB');
}

// 8. format ignores plugins when test returns false and falls back to default formatting
{
  const noopPlugin = {
    test: () => false,
    serialize: () => 'Never',
  };
  assert.equal(format({ a: 1 }, { plugins: [noopPlugin] }), 'Object {\n  "a": 1,\n}');
}

console.log('All pretty-format plugins contract assertions passed.');