@jridgewell/gen-mapping 0.3.13: GenMapping

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 @jridgewell/gen-mapping.GenMapping in pkg:npm/%40jridgewell/gen-mapping@0.3.13
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40jridgewell/gen-mapping@0.3.13
Demonstrate these symbols/APIs:
  - @jridgewell/gen-mapping.GenMapping

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:sha256:3730e2d68a9cb7e55e3159d72cad38e9244b048e445a5f437387554c3219ecf0","contract":["GenMapping initializes with optional file and sourceRoot metadata","setSourceContent stores original file source text","addMapping records 1-based generated lines with 0-based columns and symbol names","addSegment records 0-based generated positions and produces decoded segments","toEncodedMap generates valid VLQ-encoded Source Map v3 mappings","fromMap reconstructs a GenMapping instance preserving mappings and metadata","maybeAddMapping deduplicates mappings pointing to unchanged original locations"],"goal":"verify @jridgewell/gen-mapping.GenMapping in pkg:npm/%40jridgewell/gen-mapping@0.3.13","kind":"HOW","packages":["pkg:npm/%40jridgewell/gen-mapping@0.3.13"],"schemaVersion":1,"symbols":["@jridgewell/gen-mapping.GenMapping"]},"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/%40jridgewell/gen-mapping@0.3.13"],"schemaVersion":1,"subject":"pkg:npm/%40jridgewell/gen-mapping@0.3.13","symbols":["@jridgewell/gen-mapping.GenMapping"],"verifierAdapter":"node-typescript@1"}

{
  "name": "gen-mapping-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "gen-mapping-sample",
      "version": "1.0.0",
      "dependencies": {
        "@jridgewell/gen-mapping": "0.3.13"
      }
    },
    "node_modules/@jridgewell/gen-mapping": {
      "version": "0.3.13",
      "resolved": "https://registry.npmjs.org/@jridgewell/gen-mapping/-/gen-mapping-0.3.13.tgz",
      "integrity": "sha512-2kkt/7niJ6MgEPxF0bYdQ6etZaA+fQvDcLKckhy1yIQOzaoKjBBjSj63/aLVjYE3qhRt5dvM+uUyfCg6UKCBbA==",
      "license": "MIT",
      "dependencies": {
        "@jridgewell/sourcemap-codec": "^1.5.0",
        "@jridgewell/trace-mapping": "^0.3.24"
      }
    },
    "node_modules/@jridgewell/resolve-uri": {
      "version": "3.1.2",
      "resolved": "https://registry.npmjs.org/@jridgewell/resolve-uri/-/resolve-uri-3.1.2.tgz",
      "integrity": "sha512-bRISgCIjP20/tbWSPWMEi54QVPRZExkuD9lJL+UIxUKtwVJA8wW1Trb1jMs1RFXo1CBTNZ/5hpC9QvmKWdopKw==",
      "license": "MIT",
      "engines": {
        "node": ">=6.0.0"
      }
    },
    "node_modules/@jridgewell/sourcemap-codec": {
      "version": "1.6.0",
      "resolved": "https://registry.npmjs.org/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.6.0.tgz",
      "integrity": "sha512-T7jf+5zgsZHwNJ4lvQ7/aezbyk0nNX+zJVWpmHA7VYsEx7a7qr5Rg5IbtJFqkgze5Y2sruq1RUY8Q837Od7iFw==",
      "license": "MIT"
    },
    "node_modules/@jridgewell/trace-mapping": {
      "version": "0.3.31",
      "resolved": "https://registry.npmjs.org/@jridgewell/trace-mapping/-/trace-mapping-0.3.31.tgz",
      "integrity": "sha512-zzNR+SdQSDJzc8joaeP8QQoCQr8NuYx2dIIytl1QeBEZHJ9uW6hebsrYgbz8hJwUQao3TWCMtmfV8Nu1twOLAw==",
      "license": "MIT",
      "dependencies": {
        "@jridgewell/resolve-uri": "^3.1.0",
        "@jridgewell/sourcemap-codec": "^1.4.14"
      }
    }
  }
}

{
  "name": "gen-mapping-sample",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for @jridgewell/gen-mapping",
  "dependencies": {
    "@jridgewell/gen-mapping": "0.3.13"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @jridgewell/gen-mapping.GenMapping in pkg:npm/%40jridgewell/gen-mapping@0.3.13",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jridgewell/gen-mapping@0.3.13"
  ],
  "symbols": [
    "@jridgewell/gen-mapping.GenMapping"
  ]
}

import assert from 'node:assert';
import {
  GenMapping,
  addMapping,
  addSegment,
  maybeAddMapping,
  setSourceContent,
  toDecodedMap,
  toEncodedMap,
  fromMap,
} from '@jridgewell/gen-mapping';

// 1. GenMapping initializes with optional file and sourceRoot metadata
const map = new GenMapping({
  file: 'bundle.js',
  sourceRoot: 'https://example.com/src/',
});
assert.strictEqual(map.file, 'bundle.js');
assert.strictEqual(map.sourceRoot, 'https://example.com/src/');

// 2. setSourceContent stores original file source text
setSourceContent(map, 'a.js', 'console.log("hello");');
const initialDecoded = toDecodedMap(map);
assert.deepStrictEqual(initialDecoded.sources, ['a.js']);
assert.deepStrictEqual(initialDecoded.sourcesContent, ['console.log("hello");']);

// 3. addMapping records 1-based generated lines with 0-based columns and symbol names
addMapping(map, {
  generated: { line: 1, column: 0 },
  source: 'a.js',
  original: { line: 1, column: 0 },
});
addMapping(map, {
  generated: { line: 1, column: 8 },
  source: 'a.js',
  original: { line: 1, column: 8 },
  name: 'log',
});
const decoded = toDecodedMap(map);
assert.deepStrictEqual(decoded.names, ['log']);
assert.deepStrictEqual(decoded.mappings[0], [
  [0, 0, 0, 0],
  [8, 0, 0, 8, 0],
]);

// 4. addSegment records 0-based generated positions and produces decoded segments
const segMap = new GenMapping();
addSegment(segMap, 0, 0, 'b.js', 0, 0);
addSegment(segMap, 0, 5, 'b.js', 0, 5, 'foo');
const segDecoded = toDecodedMap(segMap);
assert.deepStrictEqual(segDecoded.mappings[0], [
  [0, 0, 0, 0],
  [5, 0, 0, 5, 0],
]);
assert.deepStrictEqual(segDecoded.names, ['foo']);

// 5. toEncodedMap generates valid VLQ-encoded Source Map v3 mappings
const encoded = toEncodedMap(map);
assert.strictEqual(encoded.version, 3);
assert.strictEqual(encoded.file, 'bundle.js');
assert.strictEqual(encoded.sourceRoot, 'https://example.com/src/');
assert.deepStrictEqual(encoded.sources, ['a.js']);
assert.strictEqual(typeof encoded.mappings, 'string');
assert.strictEqual(encoded.mappings, 'AAAA,QAAQA');

// 6. fromMap reconstructs a GenMapping instance preserving mappings and metadata
const imported = fromMap(encoded);
assert(imported instanceof GenMapping);
assert.deepStrictEqual(toEncodedMap(imported), encoded);

// 7. maybeAddMapping deduplicates mappings pointing to unchanged original locations
const dedupMap = new GenMapping();
maybeAddMapping(dedupMap, {
  generated: { line: 1, column: 0 },
  source: 'c.js',
  original: { line: 1, column: 0 },
});
maybeAddMapping(dedupMap, {
  generated: { line: 1, column: 4 },
  source: 'c.js',
  original: { line: 1, column: 0 },
});
const dedupDecoded = toDecodedMap(dedupMap);
assert.strictEqual(dedupDecoded.mappings[0].length, 1);

console.log('Contract passed');