Sample
Demonstrate that @babel/preset-env defaults the modules option to 'auto' and converts ES module imports and exports to CommonJS unless caller explicitly signals ESM support or modules is set to false.
sha256:3d81b247421211362cb05daf878bca49b6e2a4d4faf59815eb407dd3a95c36a1
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Case
- Goal
- Demonstrate that @babel/preset-env defaults the modules option to 'auto' and converts ES module imports and exports to CommonJS unless caller explicitly signals ESM support or modules is set to false. HOW
- Packages
- @babel/preset-env 7.26.9 @babel/core 7.26.9
- Environment
- node
- Created
- 2026-08-17T01:46:29Z
Commonly assumed
Targeting modern environments like Node 22 or setting targets.esmodules to true causes @babel/preset-env to preserve ES module import and export syntax by default without transforming them to CommonJS.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- Even when targeting modern environments that natively support ES modules such as Node 22 or esmodules: true, @babel/preset-env defaults modules to 'auto' and transforms import and export statements into CommonJS require and exports unless the caller declares supportsStaticESM or modules is explicitly set to false.
- assert default modules: 'auto' transforms import and export statements to require() and exports without a caller
- assert targeting modern node or esmodules: true still compiles ESM to CommonJS when caller does not declare supportsStaticESM
- assert dynamic import expressions are transformed to require interop unless caller declares supportsDynamicImport
- assert caller declaring supportsStaticESM: true preserves static import and export declarations as ESM syntax
- assert caller declaring supportsDynamicImport: true preserves dynamic import() expressions
- assert explicit modules: false preserves ESM import/export syntax regardless of caller metadata
- assert explicit modules: 'commonjs' transforms ESM to CommonJS even when caller declares supportsStaticESM: true
Files
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs
Download the verified artifact (tar.gz) — the exact bytes the contract ran against
Origin Seeder
Verification receipts
- node 22 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9