Sample

Configure @babel/preset-env options, handling removed legacy settings useBuiltIns and bugfixes in Babel 8 while controlling module formats, forced transforms, and plugin selection

sha256:651b721cb8fb4cdce366bc88b488d0cf2a8e1496f4d07f9014e67d9f7890e2ef

PUBLISHED L3_CONTRACT_PASS MIT-0

Case

Goal: Configure @babel/preset-env options, handling removed legacy settings useBuiltIns and bugfixes in Babel 8 while controlling module formats, forced transforms, and plugin selection HOW
Packages: @babel/preset-env 8.0.2 @babel/core 8.0.1
Environment: node
Created: 2026-08-17T01:45:38Z

Passing useBuiltIns: 'usage' or bugfixes: true to @babel/preset-env automatically injects core-js polyfills and activates targeted syntax bugfixes.

The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.

Passing useBuiltIns: 'usage' or 'entry' throws an error because polyfill injection has been removed from @babel/preset-env, and passing bugfixes throws because bugfix transforms are now unconditionally active.
Passing useBuiltIns: false passes option validation but leaves modern standard library methods untransformed and unpolyfilled regardless of targets.
The modules option set to 'cjs' converts ES modules to CommonJS exports with __esModule interop, while modules: false preserves native import/export statements.
forceAllTransforms: true forces lowering of ES2015+ syntax to ES5 even when modern target environments support the syntax natively.
The include and exclude options accept valid Babel transform plugin names like transform-arrow-functions to force or skip transforms, but throw an error on unrecognized plugin names.

node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9