flatted 3.4.3: fromJSON

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.fromJSON in pkg:npm/flatted@3.4.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/flatted@3.4.3
Demonstrate these symbols/APIs:
  - flatted.fromJSON

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:f132f14b8e3b7b22aa95004adeead27f3874a09c4ebf3bc9540c90cf53246e8a","contract":["flatted.fromJSON reconstructs primitive values from serialized flatted structure","flatted.fromJSON reconstructs standard objects and nested arrays without recursion","flatted.fromJSON reconstructs self-referencing circular object references preserving object identity","flatted.fromJSON reconstructs circular array references preserving root array identity","flatted.fromJSON reconstructs mutually circular references between multiple distinct objects","flatted.fromJSON preserves shared object references across distinct properties without duplication","flatted.fromJSON reconstructs object graphs from raw JSON-parsed flatted representation","flatted.fromJSON correctly handles empty objects and empty arrays"],"goal":"verify flatted.fromJSON in pkg:npm/flatted@3.4.3","kind":"HOW","packages":["pkg:npm/flatted@3.4.3"],"schemaVersion":1,"symbols":["flatted.fromJSON"]},"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@3.4.3"],"schemaVersion":1,"subject":"pkg:npm/flatted@3.4.3","symbols":["flatted.fromJSON"],"verifierAdapter":"node-typescript@1"}

import { fromJSON, toJSON, parse, stringify } from 'flatted';

export function restoreFromJSON(value) {
  return fromJSON(value);
}

export function roundtripFromJSON(value) {
  return fromJSON(toJSON(value));
}

export { fromJSON, toJSON, parse, stringify };
export default fromJSON;

{
  "name": "sample-flatted-fromjson",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-flatted-fromjson",
      "version": "1.0.0",
      "dependencies": {
        "flatted": "3.4.3"
      }
    },
    "node_modules/flatted": {
      "version": "3.4.3",
      "resolved": "https://registry.npmjs.org/flatted/-/flatted-3.4.3.tgz",
      "integrity": "sha512-/zipXxyO6rGvuNGDiULY9MvEGSkb2gaG4GGH4ygMi0ZZzyMHdUZBmntJmx5x1G2VuPytCwGN4xsJP6cw+sK+vQ==",
      "license": "ISC"
    }
  }
}

{
  "name": "sample-flatted-fromjson",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "flatted": "3.4.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify flatted.fromJSON in pkg:npm/flatted@3.4.3",
  "kind": "HOW",
  "packages": [
    "pkg:npm/flatted@3.4.3"
  ],
  "symbols": [
    "flatted.fromJSON"
  ]
}

import assert from 'node:assert/strict';
import { toJSON, parse, stringify } from 'flatted';
import { fromJSON, restoreFromJSON, roundtripFromJSON } from '../index.js';

// 1. flatted.fromJSON reconstructs primitive values from serialized flatted structure
{
  assert.strictEqual(fromJSON(toJSON(42)), 42);
  assert.strictEqual(fromJSON(toJSON('hello world')), 'hello world');
  assert.strictEqual(fromJSON(toJSON(true)), true);
  assert.strictEqual(fromJSON(toJSON(false)), false);
  assert.strictEqual(fromJSON(toJSON(null)), null);
  assert.strictEqual(restoreFromJSON(toJSON(100)), 100);
}

// 2. flatted.fromJSON reconstructs standard objects and nested arrays without recursion
{
  const original = {
    title: 'CodeSampleX',
    count: 10,
    tags: ['testing', 'samples', 'npm'],
    nested: { active: true, score: 99.5 }
  };
  const restored = fromJSON(toJSON(original));
  assert.deepStrictEqual(restored, original);
  assert.notStrictEqual(restored, original, 'restored object should be a new instance');
  assert.notStrictEqual(restored.nested, original.nested);
  assert.notStrictEqual(restored.tags, original.tags);
}

// 3. flatted.fromJSON reconstructs self-referencing circular object references preserving object identity
{
  const circular = { name: 'self-node', value: 1 };
  circular.self = circular;
  circular.nested = { parent: circular };

  const restored = roundtripFromJSON(circular);
  assert.strictEqual(restored.name, 'self-node');
  assert.strictEqual(restored.value, 1);
  assert.strictEqual(restored.self, restored, 'self reference must point back to restored root object');
  assert.strictEqual(restored.nested.parent, restored, 'nested parent reference must point back to restored root');
}

// 4. flatted.fromJSON reconstructs circular array references preserving root array identity
{
  const circularArr = ['root', 42];
  circularArr.push(circularArr);

  const restored = fromJSON(toJSON(circularArr));
  assert.strictEqual(Array.isArray(restored), true);
  assert.strictEqual(restored[0], 'root');
  assert.strictEqual(restored[1], 42);
  assert.strictEqual(restored[2], restored, 'array element must point back to restored array itself');
}

// 5. flatted.fromJSON reconstructs mutually circular references between multiple distinct objects
{
  const first = { label: 'first' };
  const second = { label: 'second' };
  first.partner = second;
  second.partner = first;

  const restored = fromJSON(toJSON(first));
  assert.strictEqual(restored.label, 'first');
  assert.strictEqual(restored.partner.label, 'second');
  assert.strictEqual(restored.partner.partner, restored, 'mutual circular link must be preserved');
}

// 6. flatted.fromJSON preserves shared object references across distinct properties without duplication
{
  const sharedLeaf = { leafId: 'leaf-101', timestamp: 123456 };
  const tree = {
    branchA: { item: sharedLeaf },
    branchB: { item: sharedLeaf },
    list: [sharedLeaf]
  };

  const restored = fromJSON(toJSON(tree));
  assert.strictEqual(restored.branchA.item, restored.branchB.item, 'shared reference must remain strictly identical');
  assert.strictEqual(restored.list[0], restored.branchA.item, 'list element reference must match branch item');

  // Mutating one reference should reflect on all shared points
  restored.branchA.item.leafId = 'leaf-updated';
  assert.strictEqual(restored.branchB.item.leafId, 'leaf-updated');
  assert.strictEqual(restored.list[0].leafId, 'leaf-updated');
}

// 7. flatted.fromJSON reconstructs object graphs from raw JSON-parsed flatted representation
{
  const source = { greeting: 'hello', numbers: [1, 2, 3] };
  const flattedString = stringify(source);
  const rawArray = JSON.parse(flattedString);

  assert.strictEqual(Array.isArray(rawArray), true);
  const restored = restoreFromJSON(rawArray);
  assert.deepStrictEqual(restored, source);
}

// 8. flatted.fromJSON correctly handles empty objects and empty arrays
{
  assert.deepStrictEqual(fromJSON(toJSON({})), {});
  assert.deepStrictEqual(fromJSON(toJSON([])), []);
}

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