flatted 3.4.4: stringify

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 flatted.stringify in pkg:npm/flatted@3.4.4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/flatted@3.4.4
Demonstrate these symbols/APIs:
  - flatted.stringify

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:sha256:232c6e2feaf49ea1176f2764823f814384767a944e23fb4b0553374d49bad2c5","contract":["flatted.stringify serializes circular object references without throwing TypeError","flatted.stringify serializes circular array references into indexed flatted structure","flatted.stringify preserves shared references across object properties","flatted.stringify serializes primitive values into flatted array representation","flatted.stringify supports replacer function to transform serialized values","flatted.stringify supports replacer array to filter object properties","flatted.stringify supports space parameter for formatted indentation","flatted.stringify roundtrips through flatted.parse recovering exact circular structure and identity"],"goal":"verify flatted.stringify in pkg:npm/flatted@3.4.4","kind":"HOW","packages":["pkg:npm/flatted@3.4.4"],"schemaVersion":1,"symbols":["flatted.stringify"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/flatted@3.4.4"],"schemaVersion":1,"subject":"pkg:npm/flatted@3.4.4","symbols":["flatted.stringify"],"verifierAdapter":"node-typescript@1"}

import { stringify, parse } from 'flatted';

export function stringifyCircular(value, replacer, space) {
  return stringify(value, replacer, space);
}

export function stringifyWithReplacer(value, replacer) {
  return stringify(value, replacer);
}

export function stringifyWithIndent(value, space) {
  return stringify(value, null, space);
}

export { stringify, parse };
export default stringify;

{
  "name": "sample-flatted-stringify",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-flatted-stringify",
      "version": "1.0.0",
      "dependencies": {
        "flatted": "3.4.4"
      }
    },
    "node_modules/flatted": {
      "version": "3.4.4",
      "resolved": "https://registry.npmjs.org/flatted/-/flatted-3.4.4.tgz",
      "integrity": "sha512-5+ybhBZANEJxaH3X5evAFatUxLfEHSr7n6kYJ+1Qd0mUqr4eu9gIf6GDbWHf8RJijHrjjO8G+la14SlL2SeS1Q==",
      "license": "ISC"
    }
  }
}

{
  "name": "sample-flatted-stringify",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "flatted": "3.4.4"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify flatted.stringify in pkg:npm/flatted@3.4.4",
  "kind": "HOW",
  "packages": [
    "pkg:npm/flatted@3.4.4"
  ],
  "symbols": [
    "flatted.stringify"
  ]
}

import assert from 'node:assert/strict';
import { parse } from 'flatted';
import { stringify, stringifyCircular, stringifyWithReplacer, stringifyWithIndent } from '../index.js';

// 1. flatted.stringify serializes circular object references without throwing TypeError
{
  const circularObj = { name: 'root' };
  circularObj.self = circularObj;
  circularObj.child = { parent: circularObj };

  // Standard JSON.stringify throws TypeError on circular structures
  assert.throws(() => JSON.stringify(circularObj), TypeError);

  const serialized = stringify(circularObj);
  assert.strictEqual(typeof serialized, 'string', 'serialized output must be a string');
  assert.strictEqual(stringifyCircular(circularObj), serialized);

  const raw = JSON.parse(serialized);
  assert.strictEqual(Array.isArray(raw), true, 'flatted serialized payload must be a JSON array');
  assert.strictEqual(raw[0].name, '1');
  assert.strictEqual(raw[0].self, '0', 'self reference points back to index 0');
}

// 2. flatted.stringify serializes circular array references into indexed flatted structure
{
  const circularArr = [10, 20];
  circularArr.push(circularArr);

  const serialized = stringify(circularArr);
  const raw = JSON.parse(serialized);
  assert.strictEqual(Array.isArray(raw), true, 'flatted serialized payload must be a JSON array');
  assert.strictEqual(raw[0][0], 10);
  assert.strictEqual(raw[0][1], 20);
  assert.strictEqual(raw[0][2], '0', 'self reference points back to root array index 0');
}

// 3. flatted.stringify preserves shared references across object properties
{
  const shared = { id: 'shared-node', count: 100 };
  const container = { first: shared, second: shared };

  const serialized = stringify(container);
  const raw = JSON.parse(serialized);
  assert.strictEqual(raw[0].first, raw[0].second, 'both properties must point to identical flatted index');
}

// 4. flatted.stringify serializes primitive values into flatted array representation
{
  assert.strictEqual(stringify('hello world'), '["hello world"]');
  assert.strictEqual(stringify(12345), '[12345]');
  assert.strictEqual(stringify(true), '[true]');
  assert.strictEqual(stringify(false), '[false]');
  assert.strictEqual(stringify(null), '[null]');
  assert.strictEqual(stringify(undefined), '[]');
}

// 5. flatted.stringify supports replacer function to transform serialized values
{
  const data = { x: 10, y: 20, tag: 'keep' };
  const serialized = stringifyWithReplacer(data, (key, value) => {
    if (typeof value === 'number') {
      return value * 2;
    }
    return value;
  });
  const parsed = parse(serialized);
  assert.strictEqual(parsed.x, 20, 'replacer should double numeric value x');
  assert.strictEqual(parsed.y, 40, 'replacer should double numeric value y');
  assert.strictEqual(parsed.tag, 'keep', 'replacer should preserve tag');
}

// 6. flatted.stringify supports replacer array to filter object properties
{
  const data = { a: 1, b: 2, c: 3 };
  const serialized = stringify(data, ['a', 'c']);
  const parsed = parse(serialized);
  assert.strictEqual(parsed.a, 1);
  assert.strictEqual(parsed.b, undefined, 'property b must be omitted');
  assert.strictEqual(parsed.c, 3);
}

// 7. flatted.stringify supports space parameter for formatted indentation
{
  const data = { a: 1, b: 'text' };
  const formatted = stringifyWithIndent(data, 2);
  assert.strictEqual(typeof formatted, 'string');
  assert.strictEqual(formatted.includes('\n'), true, 'formatted output should include newlines');
  assert.strictEqual(formatted.includes('  "a": 1'), true, 'formatted output should include indented properties');
}

// 8. flatted.stringify roundtrips through flatted.parse recovering exact circular structure and identity
{
  const nodeA = { name: 'NodeA' };
  const nodeB = { name: 'NodeB' };
  nodeA.neighbor = nodeB;
  nodeB.neighbor = nodeA;

  const serialized = stringify(nodeA);
  const recovered = parse(serialized);

  assert.strictEqual(recovered.name, 'NodeA');
  assert.strictEqual(recovered.neighbor.name, 'NodeB');
  assert.strictEqual(recovered.neighbor.neighbor, recovered, 'circular graph identity must be preserved across roundtrip');
}

console.log('Contract verification finished successfully.');