@jridgewell/gen-mapping 0.3.13: toDecodedMap

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.toDecodedMap 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.toDecodedMap
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:d292a7170ebe4c7e67db2247a850a11a37fc02d8f7237abc34b174063fcc23b2","constraints":{"executionContext":"node"},"contract":["toDecodedMap returns a valid v3 decoded source map structure with default fields","toDecodedMap preserves file and sourceRoot metadata","toDecodedMap extracts source file names into sources array","toDecodedMap preserves inline source contents via sourcesContent array","toDecodedMap records identifier names into names array with 5-field segment coordinates","toDecodedMap generates 4-field decoded segments for mappings without symbol names","toDecodedMap produces 1-field decoded segments for sourceless mappings","toDecodedMap preserves ignoreList indices for debugger filtering","toDecodedMap trims empty trailing lines from mappings array","toDecodedMap supports multi-line mappings sorted by generated column order"],"goal":"verify @jridgewell/gen-mapping.toDecodedMap 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.toDecodedMap"]},"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/gen-mapping@0.3.13"],"schemaVersion":1,"subject":"pkg:npm/%40jridgewell/gen-mapping@0.3.13","symbols":["@jridgewell/gen-mapping.toDecodedMap"],"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.toDecodedMap",
  "dependencies": {
    "@jridgewell/gen-mapping": "0.3.13"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @jridgewell/gen-mapping.toDecodedMap in pkg:npm/%40jridgewell/gen-mapping@0.3.13",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jridgewell/gen-mapping@0.3.13"
  ],
  "symbols": [
    "@jridgewell/gen-mapping.toDecodedMap"
  ],
  "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/strict';
import {
  GenMapping,
  addMapping,
  addSegment,
  setSourceContent,
  setIgnore,
  toDecodedMap,
} from '@jridgewell/gen-mapping';

// 1. toDecodedMap returns a valid v3 decoded source map structure with default fields
{
  const map = new GenMapping();
  const decoded = toDecodedMap(map);
  assert.equal(decoded.version, 3);
  assert.equal(decoded.file, undefined);
  assert.equal(decoded.sourceRoot, undefined);
  assert.deepEqual(decoded.sources, []);
  assert.deepEqual(decoded.names, []);
  assert.deepEqual(decoded.mappings, []);
  assert.deepEqual(decoded.ignoreList, []);
}

// 2. toDecodedMap preserves file and sourceRoot metadata
{
  const map = new GenMapping({
    file: 'bundle.js',
    sourceRoot: 'https://example.com/src/',
  });
  const decoded = toDecodedMap(map);
  assert.equal(decoded.file, 'bundle.js');
  assert.equal(decoded.sourceRoot, 'https://example.com/src/');
}

// 3. toDecodedMap extracts source file names into sources array
{
  const map = new GenMapping();
  addSegment(map, 0, 0, 'file-a.js', 0, 0);
  addSegment(map, 0, 10, 'file-b.js', 0, 0);
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.sources, ['file-a.js', 'file-b.js']);
}

// 4. toDecodedMap preserves inline source contents via sourcesContent array
{
  const map = new GenMapping();
  addSegment(map, 0, 0, 'src.js', 0, 0);
  setSourceContent(map, 'src.js', 'const x = 42;');
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.sourcesContent, ['const x = 42;']);
}

// 5. toDecodedMap records identifier names into names array with 5-field segment coordinates
{
  const map = new GenMapping();
  addMapping(map, {
    generated: { line: 1, column: 0 },
    source: 'foo.js',
    original: { line: 1, column: 0 },
    name: 'myFunction',
  });
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.names, ['myFunction']);
  assert.deepEqual(decoded.mappings, [[[0, 0, 0, 0, 0]]]);
}

// 6. toDecodedMap generates 4-field decoded segments for mappings without symbol names
{
  const map = new GenMapping();
  addMapping(map, {
    generated: { line: 1, column: 5 },
    source: 'bar.js',
    original: { line: 10, column: 2 },
  });
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.mappings, [[[5, 0, 9, 2]]]);
}

// 7. toDecodedMap produces 1-field decoded segments for sourceless mappings
{
  const map = new GenMapping();
  addSegment(map, 0, 12);
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.mappings, [[[12]]]);
}

// 8. toDecodedMap preserves ignoreList indices for debugger filtering
{
  const map = new GenMapping();
  addSegment(map, 0, 0, 'vendor/lib.js', 0, 0);
  addSegment(map, 0, 5, 'app.js', 0, 0);
  setIgnore(map, 'vendor/lib.js', true);
  const decoded = toDecodedMap(map);
  assert.deepEqual(decoded.ignoreList, [0]);
}

// 9. toDecodedMap trims empty trailing lines from mappings array
{
  const map = new GenMapping();
  addSegment(map, 0, 0, 'a.js', 0, 0);
  const decoded = toDecodedMap(map);
  assert.equal(decoded.mappings.length, 1);
  assert.deepEqual(decoded.mappings[0], [[0, 0, 0, 0]]);
}

// 10. toDecodedMap supports multi-line mappings sorted by generated column order
{
  const map = new GenMapping();
  addSegment(map, 1, 10, 'a.js', 1, 5);
  addSegment(map, 1, 0, 'a.js', 1, 0);
  addSegment(map, 0, 0, 'a.js', 0, 0);
  const decoded = toDecodedMap(map);
  assert.equal(decoded.mappings.length, 2);
  assert.deepEqual(decoded.mappings[0], [[0, 0, 0, 0]]);
  assert.deepEqual(decoded.mappings[1], [
    [0, 0, 1, 0],
    [10, 0, 1, 5],
  ]);
}

console.log('Contract passed');