diff 5.2.2: diffLines

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 diffLines in pkg:npm/diff@5.2.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/diff@5.2.2
Demonstrate these symbols/APIs:
  - diffLines

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:sha256:5c732594e85dbb4a74fb1dee485157b6be231e9c15ac8a4920e6128a77d12415","contract":["diffLines returns ordered change objects with count, value, added, and removed properties per line chunk","diffLines with ignoreWhitespace: true treats lines differing only in leading or trailing whitespace as unchanged","diffLines with newlineIsToken: true treats newline characters as separate tokens when computing line counts","diffLines with stripTrailingCr: true strips trailing carriage returns before diffing CRLF and LF inputs"],"goal":"verify diffLines in pkg:npm/diff@5.2.2","kind":"HOW","packages":["pkg:npm/diff@5.2.2"],"schemaVersion":1,"symbols":["diffLines"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","runtime":"node","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/diff@5.2.2"],"schemaVersion":1,"subject":"pkg:npm/diff@5.2.2","symbols":["diffLines"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-diff-lines",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-diff-lines",
      "version": "1.0.0",
      "dependencies": {
        "diff": "5.2.2"
      }
    },
    "node_modules/diff": {
      "version": "5.2.2",
      "resolved": "https://registry.npmjs.org/diff/-/diff-5.2.2.tgz",
      "integrity": "sha512-vtcDfH3TOjP8UekytvnHH1o1P4FcUdt4eQ1Y+Abap1tk/OB2MWQvcwS2ClCd1zuIhc3JKOx6p3kod8Vfys3E+A==",
      "license": "BSD-3-Clause",
      "engines": {
        "node": ">=0.3.1"
      }
    }
  }
}

{
  "name": "sample-diff-lines",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "diff": "5.2.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify diffLines in pkg:npm/diff@5.2.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/diff@5.2.2"
  ],
  "symbols": [
    "diffLines"
  ]
}

import { diffLines } from 'diff';

export function computeLineDiff(oldStr, newStr, options) {
  return diffLines(oldStr, newStr, options);
}

import assert from 'node:assert/strict';
import { computeLineDiff } from '../src/index.mjs';

// 1. Standard line diffing preserves trailing newlines and counts lines per chunk
const basic = computeLineDiff('alpha\nbeta\ngamma\n', 'alpha\ndelta\ngamma\n');
assert.deepEqual(basic, [
  { count: 1, value: 'alpha\n' },
  { count: 1, added: undefined, removed: true, value: 'beta\n' },
  { count: 1, added: true, removed: undefined, value: 'delta\n' },
  { count: 1, value: 'gamma\n' }
]);

// 2. Options: ignoreWhitespace treats leading/trailing whitespace differences as equal
const wsIgnored = computeLineDiff('  first\nsecond\n', 'first  \nsecond\n', {
  ignoreWhitespace: true
});
assert.equal(wsIgnored.length, 1);
assert.equal(wsIgnored[0].count, 2);
assert.equal(wsIgnored[0].added, undefined);
assert.equal(wsIgnored[0].removed, undefined);

// 3. Options: newlineIsToken emits newline characters as separate change tokens
const tokenizedNewlines = computeLineDiff('line1\nline2', 'line1\nline3', {
  newlineIsToken: true
});
assert.deepEqual(tokenizedNewlines, [
  { count: 2, value: 'line1\n' },
  { count: 1, added: undefined, removed: true, value: 'line2' },
  { count: 1, added: true, removed: undefined, value: 'line3' }
]);

// 4. Options: stripTrailingCr normalizes CRLF to LF before comparing lines
const crStripped = computeLineDiff('a\r\nb\r\n', 'a\nb\n', {
  stripTrailingCr: true
});
assert.deepEqual(crStripped, [
  { count: 2, value: 'a\nb\n' }
]);