fast-json-stable-stringify 2.1.0: 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 stringify in pkg:npm/fast-json-stable-stringify@2.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/fast-json-stable-stringify@2.1.0
Demonstrate these symbols/APIs:
  - 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:ee0f51b30675b0b7871e0c2fc6fd582f979630605d4913483998d447d1e3bedd","contract":["assert stringify produces deterministic JSON string with sorted keys regardless of property insertion order","assert stringify handles nested objects and arrays deterministically","assert stringify supports custom key comparison function via cmp option","assert stringify throws TypeError on circular references by default and replaces cycles with __cycle__ when cycles option is true","assert stringify correctly serializes primitive values, null, and omits undefined or functions in objects while converting them to null in arrays"],"goal":"verify stringify in pkg:npm/fast-json-stable-stringify@2.1.0","kind":"HOW","packages":["pkg:npm/fast-json-stable-stringify@2.1.0"],"schemaVersion":1,"symbols":["stringify"]},"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/fast-json-stable-stringify@2.1.0"],"schemaVersion":1,"subject":"pkg:npm/fast-json-stable-stringify@2.1.0","symbols":["stringify"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-fast-json-stable-stringify",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-fast-json-stable-stringify",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "fast-json-stable-stringify": "2.1.0"
      }
    },
    "node_modules/fast-json-stable-stringify": {
      "version": "2.1.0",
      "resolved": "https://registry.npmjs.org/fast-json-stable-stringify/-/fast-json-stable-stringify-2.1.0.tgz",
      "integrity": "sha512-lhd/wF+Lk98HZoTCtlVraHtfh5XYijIjalXck7saUtuanSDyLMxnHhSXEDJqHxD7msR8D0uCmqlkwjCV8xvwHw==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-fast-json-stable-stringify",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "fast-json-stable-stringify": "2.1.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify stringify in pkg:npm/fast-json-stable-stringify@2.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/fast-json-stable-stringify@2.1.0"
  ],
  "symbols": [
    "stringify"
  ]
}

import assert from 'node:assert/strict';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const stringify = require('fast-json-stable-stringify');

// 1. Deterministic JSON string with sorted keys regardless of property insertion order
const obj1 = { c: 3, a: 1, b: 2 };
const obj2 = { b: 2, c: 3, a: 1 };
assert.equal(stringify(obj1), '{"a":1,"b":2,"c":3}');
assert.equal(stringify(obj2), '{"a":1,"b":2,"c":3}');
assert.equal(stringify(obj1), stringify(obj2));

// 2. Nested objects and arrays deterministically handled
const nested1 = { z: { b: 1, a: 2 }, list: [{ d: 4, c: 3 }] };
const nested2 = { list: [{ c: 3, d: 4 }], z: { a: 2, b: 1 } };
assert.equal(stringify(nested1), '{"list":[{"c":3,"d":4}],"z":{"a":2,"b":1}}');
assert.equal(stringify(nested1), stringify(nested2));

// 3. Custom comparison function via cmp option
const customCmp = (a, b) => (a.key < b.key ? 1 : -1);
const reversed = stringify({ a: 1, b: 2, c: 3 }, { cmp: customCmp });
assert.equal(reversed, '{"c":3,"b":2,"a":1}');

// 4. Circular structures: throws TypeError by default, handles cycles when cycles: true
const circularObj = { name: 'cycle-test' };
circularObj.self = circularObj;

assert.throws(
  () => stringify(circularObj),
  (err) => err instanceof TypeError && /circular structure/.test(err.message)
);

const withCycles = stringify(circularObj, { cycles: true });
assert.equal(withCycles, '{"name":"cycle-test","self":"__cycle__"}');

// 5. Primitive values, null, undefined, functions
assert.equal(stringify(42), '42');
assert.equal(stringify('hello'), '"hello"');
assert.equal(stringify(true), 'true');
assert.equal(stringify(null), 'null');
assert.equal(stringify(undefined), undefined);

// Undefined and functions are omitted in objects
assert.equal(stringify({ a: 1, b: undefined, c: () => {}, d: 'val' }), '{"a":1,"d":"val"}');

// Undefined and functions are converted to null in arrays
assert.equal(stringify([1, undefined, () => {}, 'val']), '[1,null,null,"val"]');