Пример

Demonstrate that @babel/preset-env defaults useBuiltIns to false, performing syntax-only transpilation without polyfilling missing built-in APIs unless explicitly configured.

sha256:8f91486f2c59f67a07afd45b8a3a5988da85d7f85f7f3347a1c43d8e1c5c1a31

PUBLISHED L3_CONTRACT_PASS MIT-0

Кейс

Цель: Demonstrate that @babel/preset-env defaults useBuiltIns to false, performing syntax-only transpilation without polyfilling missing built-in APIs unless explicitly configured. HOW
Пакеты: @babel/preset-env 7.29.7 @babel/core 7.29.7 core-js 3.50.0
Окружение: node
Создан: 2026-08-16T15:46:58Z

Что обычно предполагают

Leaving useBuiltIns unset in @babel/preset-env automatically injects polyfills for unsupported ECMAScript standard library methods across configured target environments when corejs is configured or core-js is imported.

Автор образца записал здесь то, чего ожидал бы разработчик или модель. Контракт ниже — это то, что действительно выполнялось.

Контракт

When useBuiltIns is unset, @babel/preset-env defaults to false and leaves standard library methods un-polyfilled without injecting any core-js imports, even when targets lack support or corejs is specified.
assert leaving useBuiltIns unset leaves built-in methods like Array.prototype.flat, Object.fromEntries, and Promise.allSettled completely un-polyfilled without core-js module imports
assert specifying corejs alone without enabling useBuiltIns has no effect on polyfill injection
assert leaving useBuiltIns unset preserves raw core-js entry imports rather than splitting them into per-target polyfill imports
assert useBuiltIns: 'usage' with corejs scans AST usage and injects only the required core-js module imports
assert useBuiltIns: 'entry' with corejs replaces monolithic core-js imports with target-specific individual polyfill imports

Файлы

NOTES.md
csx.json
package-lock.json
package.json
test/contract.mjs

Скачать проверенный артефакт (tar.gz) — те самые байты, на которых выполнялся контракт

Исходный сидер

csx-seed

Квитанции проверки

node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-16 · ed25519:d91480838ac982c9