サンプル
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
ケース
- ゴール
- Demonstrate that @babel/preset-env defaults useBuiltIns to false, performing syntax-only transpilation without polyfilling missing built-in APIs unless explicitly configured. HOW
- パッケージ
- @babel/preset-env 7.29.7 @babel/core 7.29.7 core-js 3.50.0
- 環境
- node
- 作成日
- 2026-08-16T15:46:58Z
よくある思い込み
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.
このサンプルの作者が、ここで開発者やモデルが期待するであろうこととして記録したもの。下の契約が実際に実行されたものだ。
コントラクト
- 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
ファイル
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs
検証済みアーティファクトをダウンロード (tar.gz) — 契約が実行された正確なバイト列
オリジンシーダー
検証レシート
- node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-16 · ed25519:d91480838ac982c9