@vitest/utils 4.1.10: format

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 @vitest/utils.format in pkg:npm/%40vitest/utils@4.1.10
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40vitest/utils@4.1.10
Demonstrate these symbols/APIs:
  - @vitest/utils.format

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:c6d4ed54dfbafb5d1ca8089c7a3e3d585a22295e5194d9c3f923bfa75b388593","contract":["format replaces %s specifiers with formatted strings, BigInt literals, negative zero, and custom object representations","format replaces %d, %i, and %f specifiers with numbers, parsed integers, and floating-point representations","format serializes objects with %j and handles circular references by replacing them with [Circular]","format replaces %% with a literal percent sign without consuming an argument","format consumes %c arguments as CSS directives and outputs an empty string","format appends excess arguments separated by spaces and preserves unmatched format specifiers","format inspects and joins multiple arguments with spaces when the first argument is not a string"],"goal":"verify @vitest/utils.format in pkg:npm/%40vitest/utils@4.1.10","kind":"HOW","packages":["pkg:npm/%40vitest/utils@4.1.10"],"schemaVersion":1,"symbols":["@vitest/utils.format"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40vitest/utils@4.1.10"],"schemaVersion":1,"subject":"pkg:npm/%40vitest/utils@4.1.10","symbols":["@vitest/utils.format"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-vitest-utils-format",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-vitest-utils-format",
      "version": "1.0.0",
      "dependencies": {
        "@vitest/utils": "4.1.10"
      }
    },
    "node_modules/@vitest/pretty-format": {
      "version": "4.1.10",
      "resolved": "https://registry.npmjs.org/@vitest/pretty-format/-/pretty-format-4.1.10.tgz",
      "integrity": "sha512-W1HsjSH4MXQ9YfmmhLAoIYf1HRfekQCGngeIgcei6MP5QQGWUe0gkopdZQaVCFO+JDJMrAJGwa5pRpNpvy4P8Q==",
      "license": "MIT",
      "dependencies": {
        "tinyrainbow": "^3.1.0"
      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/@vitest/utils": {
      "version": "4.1.10",
      "resolved": "https://registry.npmjs.org/@vitest/utils/-/utils-4.1.10.tgz",
      "integrity": "sha512-fy9am/HWxbaGt/Sawrp90vt6Y6jQwf1RX77cz3uwoJwJVMli/e1IEwRPnMNJ7vKfPTwo0diXifkpPvwH9v7nGA==",
      "license": "MIT",
      "dependencies": {
        "@vitest/pretty-format": "4.1.10",
        "convert-source-map": "^2.0.0",
        "tinyrainbow": "^3.1.0"
      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/convert-source-map": {
      "version": "2.0.0",
      "resolved": "https://registry.npmjs.org/convert-source-map/-/convert-source-map-2.0.0.tgz",
      "integrity": "sha512-Kvp459HrV2FEJ1CAsi1Ku+MY3kasH19TFykTz2xWmMeq6bk2NU3XXvfJ+Q61m0xktWwt+1HSYf3JZsTms3aRJg==",
      "license": "MIT"
    },
    "node_modules/tinyrainbow": {
      "version": "3.1.1",
      "resolved": "https://registry.npmjs.org/tinyrainbow/-/tinyrainbow-3.1.1.tgz",
      "integrity": "sha512-yau8yJdTt989Mm0Bd/236QnzEiPf2xLLTqUZRUJOo/3CB078LSwzei343DgtJVmfJKJE3TMINY1u42SQsP6mXw==",
      "license": "MIT",
      "engines": {
        "node": ">=14.0.0"
      }
    }
  }
}

{
  "name": "sample-vitest-utils-format",
  "version": "1.0.0",
  "private": true,
  "description": "verify @vitest/utils.format in pkg:npm/@vitest/utils@4.1.10",
  "type": "module",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "@vitest/utils": "4.1.10"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @vitest/utils.format in pkg:npm/%40vitest/utils@4.1.10",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40vitest/utils@4.1.10"
  ],
  "symbols": [
    "@vitest/utils.format"
  ]
}

import { format } from '@vitest/utils/display';

/**
 * Formats a message string using printf-style specifiers or inspects multiple arguments.
 * @param {...unknown} args
 * @returns {string}
 */
export function formatMessage(...args) {
  return format(...args);
}

export { format };
export default format;

import assert from 'node:assert/strict';
import { format } from '@vitest/utils/display';
import { formatMessage } from '../src/index.js';

// 1. format replaces %s specifiers with formatted strings, BigInt literals, negative zero, and custom object representations
assert.equal(format('%s', 'vitest'), 'vitest');
assert.equal(format('Hello %s', 'world'), 'Hello world');
assert.equal(format('%s', 123n), '123n');
assert.equal(format('%s', -0), '-0');
assert.equal(format('%s', { toString() { return 'custom-repr'; } }), 'custom-repr');
assert.equal(format('%s', { a: 1 }), '{ a: 1 }');
assert.equal(formatMessage('Value: %s', 'wrapped'), 'Value: wrapped');

// 2. format replaces %d, %i, and %f specifiers with numbers, parsed integers, and floating-point representations
assert.equal(format('%d and %d', 42.5, 99n), '42.5 and 99n');
assert.equal(format('%d', Symbol('s')), 'NaN');
assert.equal(format('%i', '42.9px'), '42');
assert.equal(format('%i', 88n), '88n');
assert.equal(format('%f', '3.14159'), '3.14159');

// 3. format serializes objects with %j and handles circular references by replacing them with [Circular]
assert.equal(format('%j', { id: 10, ok: true }), '{"id":10,"ok":true}');
const circular = {};
circular.self = circular;
assert.equal(format('%j', circular), '[Circular]');

// 4. format replaces %% with a literal percent sign without consuming an argument
assert.equal(format('rate: %d%%', 100), 'rate: 100%');
assert.equal(format('%% alone'), '% alone');
assert.equal(format('%% %s', 'escaped'), '% escaped');

// 5. format consumes %c arguments as CSS directives and outputs an empty string
assert.equal(format('%cTitle %s', 'color: blue', 'text'), 'Title text');
assert.equal(format('%c', 'font-weight: bold'), '');

// 6. format appends excess arguments separated by spaces and preserves unmatched format specifiers
assert.equal(format('%s and %s', 'first'), 'first and %s');
assert.equal(format('Hello', 'world', 123), 'Hello world 123');
assert.equal(format('Prefix: %s', 'arg', 'extra1', { k: 'v' }), "Prefix: arg extra1 { k: 'v' }");

// 7. format inspects and joins multiple arguments with spaces when the first argument is not a string
assert.equal(format({ a: 1 }, [1, 2]), '{ a: 1 } [ 1, 2 ]');
assert.equal(format(42, 'str'), "42 'str'");
assert.equal(format(null, undefined, true), 'null undefined true');

console.log('All @vitest/utils.format contract assertions passed.');