@jridgewell/sourcemap-codec 1.5.5: encode

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 encode in pkg:npm/%40jridgewell/sourcemap-codec@1.5.5
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40jridgewell/sourcemap-codec@1.5.5
Demonstrate these symbols/APIs:
  - encode
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:a85a92d3047730331698b2ae7cbe9d3f3a4edcc180365526b4c850034e5c5e48","constraints":{"executionContext":"node"},"contract":["assert encode returns empty string for empty mappings","assert encode separates empty lines with semicolons","assert encode encodes single-field segments containing only generated column","assert encode encodes 4-field segments containing generated column source index original line and original column","assert encode encodes 5-field segments containing name index and applies relative delta encoding","assert encode correctly encodes multi-line mappings and roundtrips with decode"],"goal":"verify encode in pkg:npm/%40jridgewell/sourcemap-codec@1.5.5","kind":"HOW","packages":["pkg:npm/%40jridgewell/sourcemap-codec@1.5.5"],"schemaVersion":1,"symbols":["encode"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40jridgewell/sourcemap-codec@1.5.5"],"schemaVersion":1,"subject":"pkg:npm/%40jridgewell/sourcemap-codec@1.5.5","symbols":["encode"],"verifierAdapter":"node-typescript@1"}

const { encode, decode } = require('@jridgewell/sourcemap-codec');

/**
 * Encodes decoded source map line segments into a VLQ mapping string.
 *
 * @param {Array<Array<Array<number>>>} decoded - Decoded source map mappings.
 * @returns {string} Encoded source map mappings string.
 */
function encodeMappings(decoded) {
  return encode(decoded);
}

module.exports = {
  encodeMappings,
  encode,
  decode,
};

{
  "name": "sample-sourcemap-codec-encode",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-sourcemap-codec-encode",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "@jridgewell/sourcemap-codec": "1.5.5"
      }
    },
    "node_modules/@jridgewell/sourcemap-codec": {
      "version": "1.5.5",
      "resolved": "https://registry.npmjs.org/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.5.5.tgz",
      "integrity": "sha512-cYQ9310grqxueWbl+WuIUIaiUaDcj7WOq5fVhEljNVgRfOUhY9fy2zTvfoqWsnebh8Sl70VScFbICvJnLKB0Og==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-sourcemap-codec-encode",
  "version": "1.0.0",
  "description": "Clean-room sample verifying encode in @jridgewell/sourcemap-codec",
  "main": "index.js",
  "license": "MIT-0",
  "dependencies": {
    "@jridgewell/sourcemap-codec": "1.5.5"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify encode in pkg:npm/%40jridgewell/sourcemap-codec@1.5.5",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jridgewell/sourcemap-codec@1.5.5"
  ],
  "symbols": [
    "encode"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert';
import { encode, decode } from '@jridgewell/sourcemap-codec';
import { encodeMappings } from '../index.js';

// 1. Encode empty line mappings returns empty string
assert.strictEqual(encodeMappings([]), '', 'encode must return empty string for empty mappings');

// 2. Encode lines with empty segment arrays separated by semicolons
assert.strictEqual(
  encodeMappings([[], []]),
  ';',
  'encode must separate empty lines with semicolons'
);
assert.strictEqual(
  encodeMappings([[], [], []]),
  ';;',
  'encode must generate consecutive semicolons for multiple empty lines'
);

// 3. Encode single-field segments (generated column only)
assert.strictEqual(
  encodeMappings([[[0]], [[5]]]),
  'A;K',
  'encode must encode 1-field segments with generated column only'
);

// 4. Encode 4-field segments with generated column, source index, original line, original column
assert.strictEqual(
  encodeMappings([[[0, 0, 0, 0]]]),
  'AAAA',
  'encode must encode standard 4-field segment'
);
assert.strictEqual(
  encodeMappings([[[0, 0, 0, 0], [4, 0, 0, 4]]]),
  'AAAA,IAAI',
  'encode must encode multiple segments per line with comma separation and relative delta encoding'
);

// 5. Encode 5-field segments including name index
assert.strictEqual(
  encodeMappings([[[0, 0, 0, 0, 0]]]),
  'AAAAA',
  'encode must encode 5-field segment with name index'
);
assert.strictEqual(
  encodeMappings([[[0, 0, 0, 0, 0], [4, 0, 0, 4, 1]]]),
  'AAAAA,IAAIC',
  'encode must delta-encode name index across adjacent 5-field segments'
);

// 6. Encode multi-line mappings and verify roundtrip decoding
const complexMappings = [
  [[0, 0, 0, 0]],
  [[0, 0, 1, 0]],
  [[2, 0, 2, 5, 0]],
];
const encodedString = encodeMappings(complexMappings);
assert.strictEqual(
  encodedString,
  'AAAA;AACA;EACKA',
  'encode must encode complex multiline mappings with correct state offsets'
);
assert.deepStrictEqual(
  decode(encodedString),
  complexMappings,
  'decode must roundtrip correctly with encode output'
);

console.log('All sourcemap-codec encode contract assertions passed.');