@vitest/utils 4.1.10: diff

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.diff 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.diff

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:c9372bd10667f8a5d090cbb61d9bc501789b6e00fdd3615f9cb6493db6dc5ef8","contract":["diff returns empty string when comparing identical primitive strings","diff highlights differences between distinct primitive values with default annotations","diff formats visual difference between structured objects with modified properties","diff reports no visual difference message when comparing deeply equal distinct objects","diff applies custom aAnnotation and bAnnotation header labels","diff supports omitAnnotationLines and includeChangeCounts formatting options","diffStringsUnified computes unified diff between multiline strings","diffStringsRaw returns raw diff operations with DIFF_EQUAL, DIFF_DELETE, and DIFF_INSERT constants"],"goal":"verify @vitest/utils.diff in pkg:npm/%40vitest/utils@4.1.10","kind":"HOW","packages":["pkg:npm/%40vitest/utils@4.1.10"],"schemaVersion":1,"symbols":["@vitest/utils.diff"]},"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/%40vitest/utils@4.1.10"],"schemaVersion":1,"subject":"pkg:npm/%40vitest/utils@4.1.10","symbols":["@vitest/utils.diff"],"verifierAdapter":"node-typescript@1"}

{
  "name": "vitest-utils-diff-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "vitest-utils-diff-sample",
      "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": "vitest-utils-diff-sample",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for @vitest/utils diff",
  "type": "module",
  "dependencies": {
    "@vitest/utils": "4.1.10"
  }
}

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

import assert from 'node:assert';
import {
  diff,
  diffStringsUnified,
  diffStringsRaw,
  Diff,
  DIFF_DELETE,
  DIFF_INSERT,
  DIFF_EQUAL
} from '@vitest/utils/diff';

const stripAnsi = (str) => typeof str === 'string' ? str.replace(/\x1B\[\d+m/g, '') : '';

// 1. diff returns empty string when comparing identical primitive strings
assert.strictEqual(diff('identical', 'identical'), '');
assert.strictEqual(diff(12345, 12345), '');
assert.strictEqual(diff(true, true), '');

// 2. diff highlights differences between distinct primitive values with default annotations
const primitiveDiff = diff('expected-val', 'received-val');
assert.ok(typeof primitiveDiff === 'string' && primitiveDiff.length > 0);
const cleanPrimitiveDiff = stripAnsi(primitiveDiff);
assert.match(cleanPrimitiveDiff, /- Expected/);
assert.match(cleanPrimitiveDiff, /\+ Received/);
assert.match(cleanPrimitiveDiff, /- expected-val/);
assert.match(cleanPrimitiveDiff, /\+ received-val/);

// 3. diff formats visual difference between structured objects with modified properties
const objDiff = diff({ id: 1, status: 'open' }, { id: 1, status: 'closed' });
assert.ok(typeof objDiff === 'string');
const cleanObjDiff = stripAnsi(objDiff);
assert.match(cleanObjDiff, /-   "status": "open"/);
assert.match(cleanObjDiff, /\+   "status": "closed"/);

// 4. diff reports no visual difference message when comparing deeply equal distinct objects
const equalObjDiff = diff({ x: 10, y: [1, 2] }, { x: 10, y: [1, 2] });
assert.ok(typeof equalObjDiff === 'string');
const cleanEqualObjDiff = stripAnsi(equalObjDiff);
assert.match(cleanEqualObjDiff, /Compared values have no visual difference/);

// 5. diff applies custom aAnnotation and bAnnotation header labels
const customAnnotDiff = diff(
  { count: 1 },
  { count: 2 },
  { aAnnotation: 'Before', bAnnotation: 'After' }
);
const cleanCustomAnnot = stripAnsi(customAnnotDiff);
assert.match(cleanCustomAnnot, /- Before/);
assert.match(cleanCustomAnnot, /\+ After/);

// 6. diff supports omitAnnotationLines and includeChangeCounts formatting options
const omitted = diff('alpha', 'beta', { omitAnnotationLines: true });
const cleanOmitted = stripAnsi(omitted);
assert.ok(!cleanOmitted.includes('Expected') && !cleanOmitted.includes('Received'));
assert.match(cleanOmitted, /- alpha/);
assert.match(cleanOmitted, /\+ beta/);

const counted = diff('alpha', 'beta', { includeChangeCounts: true });
const cleanCounted = stripAnsi(counted);
assert.match(cleanCounted, /- Expected  - 1/);
assert.match(cleanCounted, /\+ Received  \+ 1/);

// 7. diffStringsUnified computes unified diff between multiline strings
const multilineDiff = diffStringsUnified('alpha\nbeta', 'alpha\ngamma');
assert.ok(typeof multilineDiff === 'string');
const cleanMultiline = stripAnsi(multilineDiff);
assert.match(cleanMultiline, /- beta/);
assert.match(cleanMultiline, /\+ gamma/);

// 8. diffStringsRaw returns raw diff operations with DIFF_EQUAL, DIFF_DELETE, and DIFF_INSERT constants
const [diffs, truncated] = diffStringsRaw('cat', 'car', true);
assert.strictEqual(truncated, false);
assert.strictEqual(diffs.length, 3);
assert.ok(diffs[0] instanceof Diff || diffs[0][0] !== undefined);
assert.strictEqual(DIFF_EQUAL, 0);
assert.strictEqual(DIFF_DELETE, -1);
assert.strictEqual(DIFF_INSERT, 1);
assert.strictEqual(diffs[0][0], DIFF_EQUAL);
assert.strictEqual(diffs[0][1], 'ca');
assert.strictEqual(diffs[1][0], DIFF_DELETE);
assert.strictEqual(diffs[1][1], 't');
assert.strictEqual(diffs[2][0], DIFF_INSERT);
assert.strictEqual(diffs[2][1], 'r');

console.log('Contract passed');