This repository serves as a reproduction for a bug concerning module resolution in Node16, specifically when transpiling a mixed TypeScript/JavaScript file set using Node16/NodeNext as module/moduleResolution.
I expect tsc to produce __esModule transpilation marker only for modules that are NOT CommonJS as source, but CommonJS as final target. All else results in failed synthetic default import detection:
From TS file:
import syntheticDefault from './commonjs.cjs'
// syntheticDefault is now undefined!
- Clone this repository.
- Run
npm installto install the necessary dependencies. - Run
npm run buildto start the build process. - Check the output files in
dist/
All files transpiled from ESM to CJS should have a transpilation marker. No other files should have the marker.
The full test matrix is as follows:
Expected result:
| Source | Target ESM | Target CJS |
|---|---|---|
| JS-ESM | ? | M |
| JS-CJS | - | - |
| TS-ESM | - | M |
| TS-CJS | ? | - |
Actual result:
| Source | Target ESM | Target CJS |
|---|---|---|
| JS-ESM | X | M |
| JS-CJS | - | M |
| TS-ESM | - | M |
| TS-CJS | X | - |
Symbols:
-
- = No marker, no error
- M = Marker, no error
- X = Error (file did not transpile or causes bad transpiled code)
- ? = Should potentially be trated as error? Not sure, out of scope of this bug
Make sure to never rely of synthetic default imports in mixed ts/js node16 projects that rely on legacy CommonJS sources.
Alexander Schrab alexander.schrab@gmail.com