type-fest 0.13.1: ConditionalExcept

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 type-fest.ConditionalExcept in pkg:npm/type-fest@0.13.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/type-fest@0.13.1
Demonstrate these symbols/APIs:
  - type-fest.ConditionalExcept

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:sha256:0ba36f8666292b5213b4f7ac5ba6083bcafc0b376b7f77591d81c5d1fa31f122","contract":["type-fest package.json defines package name as type-fest and version as 0.13.1 with types entry point","type-fest index declarations export ConditionalExcept symbol","ConditionalExcept type definition delegates to Except utility and ConditionalKeys helper","ConditionalKeys type definition maps object keys filtering for types matching condition using distributive conditional type","Except type definition restricts omitted keys to target object keys using Pick and Exclude"],"goal":"verify type-fest.ConditionalExcept in pkg:npm/type-fest@0.13.1","kind":"HOW","packages":["pkg:npm/type-fest@0.13.1"],"schemaVersion":1,"symbols":["type-fest.ConditionalExcept"]},"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/type-fest@0.13.1"],"schemaVersion":1,"subject":"pkg:npm/type-fest@0.13.1","symbols":["type-fest.ConditionalExcept"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-type-fest-conditional-except",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-type-fest-conditional-except",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "type-fest": "0.13.1"
      }
    },
    "node_modules/type-fest": {
      "version": "0.13.1",
      "resolved": "https://registry.npmjs.org/type-fest/-/type-fest-0.13.1.tgz",
      "integrity": "sha512-34R7HTnG0XIJcBSn5XhDd7nNFPRcXYRZrBB2O2jdKqYODldSzBAqzsWoZYYvduky73toYS/ESqxPvkDf/F0XMg==",
      "license": "(MIT OR CC0-1.0)",
      "engines": {
        "node": ">=10"
      },
      "funding": {
        "url": "https://github.com/sponsors/sindresorhus"
      }
    }
  }
}

{
  "name": "sample-type-fest-conditional-except",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "license": "MIT-0",
  "dependencies": {
    "type-fest": "0.13.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify type-fest.ConditionalExcept in pkg:npm/type-fest@0.13.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/type-fest@0.13.1"
  ],
  "symbols": [
    "type-fest.ConditionalExcept"
  ]
}

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

const require = createRequire(import.meta.url);

// Contract 1: type-fest package.json defines package name as type-fest and version as 0.13.1 with types entry point
{
  const pkgJson = require('type-fest/package.json');
  assert.equal(pkgJson.name, 'type-fest');
  assert.equal(pkgJson.version, '0.13.1');
  assert.equal(pkgJson.types, 'index.d.ts');
}

// Contract 2: type-fest index declarations export ConditionalExcept symbol
{
  const pkgDir = path.dirname(require.resolve('type-fest/package.json'));
  const indexDtsPath = path.join(pkgDir, 'index.d.ts');
  assert.ok(fs.existsSync(indexDtsPath), 'index.d.ts must exist');
  const indexDtsContent = fs.readFileSync(indexDtsPath, 'utf8');
  assert.ok(
    indexDtsContent.includes("export {ConditionalExcept} from './source/conditional-except';"),
    'ConditionalExcept must be exported from index.d.ts'
  );
}

// Contract 3: ConditionalExcept type definition delegates to Except utility and ConditionalKeys helper
{
  const pkgDir = path.dirname(require.resolve('type-fest/package.json'));
  const condExceptDtsPath = path.join(pkgDir, 'source', 'conditional-except.d.ts');
  assert.ok(fs.existsSync(condExceptDtsPath), 'source/conditional-except.d.ts must exist');
  const condExceptDtsContent = fs.readFileSync(condExceptDtsPath, 'utf8');
  assert.ok(
    condExceptDtsContent.includes("import {Except} from './except';"),
    'conditional-except.d.ts must import Except'
  );
  assert.ok(
    condExceptDtsContent.includes("import {ConditionalKeys} from './conditional-keys';"),
    'conditional-except.d.ts must import ConditionalKeys'
  );
  assert.ok(
    condExceptDtsContent.includes('export type ConditionalExcept<Base, Condition> = Except<'),
    'ConditionalExcept must be defined as Except over Base'
  );
  assert.ok(
    condExceptDtsContent.includes('ConditionalKeys<Base, Condition>'),
    'ConditionalExcept must exclude ConditionalKeys matching Condition'
  );
}

// Contract 4: ConditionalKeys type definition maps object keys filtering for types matching condition using distributive conditional type
{
  const pkgDir = path.dirname(require.resolve('type-fest/package.json'));
  const condKeysDtsPath = path.join(pkgDir, 'source', 'conditional-keys.d.ts');
  assert.ok(fs.existsSync(condKeysDtsPath), 'source/conditional-keys.d.ts must exist');
  const condKeysDtsContent = fs.readFileSync(condKeysDtsPath, 'utf8');
  assert.ok(
    condKeysDtsContent.includes('export type ConditionalKeys<Base, Condition> = NonNullable<'),
    'ConditionalKeys must wrap result in NonNullable'
  );
  assert.ok(
    condKeysDtsContent.includes('[Key in keyof Base]:'),
    'ConditionalKeys must map across keyof Base'
  );
  assert.ok(
    condKeysDtsContent.includes('Base[Key] extends Condition'),
    'ConditionalKeys must check if property type extends Condition'
  );
}

// Contract 5: Except type definition restricts omitted keys to target object keys using Pick and Exclude
{
  const pkgDir = path.dirname(require.resolve('type-fest/package.json'));
  const exceptDtsPath = path.join(pkgDir, 'source', 'except.d.ts');
  assert.ok(fs.existsSync(exceptDtsPath), 'source/except.d.ts must exist');
  const exceptDtsContent = fs.readFileSync(exceptDtsPath, 'utf8');
  assert.ok(
    exceptDtsContent.includes('export type Except<ObjectType, KeysType extends keyof ObjectType>'),
    'Except must constrain KeysType to keyof ObjectType'
  );
  assert.ok(
    exceptDtsContent.includes('Pick<ObjectType, Exclude<keyof ObjectType, KeysType>>'),
    'Except must use Pick and Exclude'
  );
}

console.log('All pkg:npm/type-fest@0.13.1 contracts passed successfully.');