diff 5.2.2: parsePatch

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 diff.parsePatch 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:
  - diff.parsePatch

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:sha256:3d56c9a1f75209aa65dce514ecca3372847922cefa0cf25418203b814cdf0713","contract":["parsePatch(uniDiff) parses unified diff text into an array of patch objects containing index, oldFileName, newFileName, oldHeader, newHeader, and hunks","each parsed hunk includes oldStart, oldLines, newStart, newLines, lines, and linedelimiters","parsePatch(uniDiff, { strict: true }) throws an Error when hunk line counts do not match the hunk header"],"goal":"verify diff.parsePatch in pkg:npm/diff@5.2.2","kind":"HOW","packages":["pkg:npm/diff@5.2.2"],"schemaVersion":1,"symbols":["diff.parsePatch"]},"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/diff@5.2.2"],"schemaVersion":1,"subject":"pkg:npm/diff@5.2.2","symbols":["diff.parsePatch"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample",
      "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",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "diff": "5.2.2"
  }
}

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

import assert from "node:assert/strict";
import { parsePatch } from "diff";

const unifiedDiff = [
  "Index: sample.txt",
  "===================================================================",
  "--- sample.txt\told-rev",
  "+++ sample.txt\tnew-rev",
  "@@ -1,3 +1,3 @@",
  " line1",
  "-line2",
  "+line2-modified",
  " line3",
].join("\n");

const parsed = parsePatch(unifiedDiff);

assert.equal(Array.isArray(parsed), true);
assert.equal(parsed.length, 1);
assert.equal(parsed[0].index, "sample.txt");
assert.equal(parsed[0].oldFileName, "sample.txt");
assert.equal(parsed[0].newFileName, "sample.txt");
assert.equal(parsed[0].oldHeader, "old-rev");
assert.equal(parsed[0].newHeader, "new-rev");
assert.equal(parsed[0].hunks.length, 1);
assert.deepEqual(parsed[0].hunks[0], {
  oldStart: 1,
  oldLines: 3,
  newStart: 1,
  newLines: 3,
  lines: [" line1", "-line2", "+line2-modified", " line3"],
  linedelimiters: ["\n", "\n", "\n", "\n"],
});

assert.throws(
  () =>
    parsePatch(
      [
        "--- sample.txt",
        "+++ sample.txt",
        "@@ -1,2 +1,2 @@",
        " only-one-line",
      ].join("\n"),
      { strict: true }
    ),
  /Added line count did not match for hunk at line 3/
);