dkebler / core-esm-named-import-error

repo to show how core esm can not do a named import from a cjs module using dot export

Demonstrating that core esm support in V14 does not support a named import of a cjs dot export even though esm support via std/esm package does.

the std/esm support can import cjs dot exports as named imports just fine but core esm v14 support cannot.

This is a repo that allows recreating the issue with esm support of dot exports in cjs modules in V14 when using the "type": "module" key in package.json and how this is not an issue using esm support via std/esm.

How

clone repo, install.

there are flavors of package.json, one with "type": "module" for running core esm support in V14 and one without designed to be run with the std/esm package using the flag -r esm

Runing using core esm support in V14

To use with esm support in V14 copy esm-package.json to package.json do the same within the esm-module package which is a folder in this repo

delete /node_modules and run npm-install

then npm start

you will get this error

file:///mnt/AllData/hacking/active-dev-repos/name-import-error/index.js:5
import { cjsDotExport as cjs } from 'example-cjs-module'
         ^^^^^^^^^^^^
SyntaxError: The requested module 'example-cjs-module' does not provide an export named 'cjsDotExport'

now comment out the lines in index.js

// import { cjsDotExport as cjs } from 'example-cjs-module'
// cjs()

run again npm start and you will see that the esm-module loads correctly using the "type": "module" in it's package.json and outputs Hello from esm module

Running using std/esm package

To see the cjs module work as a named import with std/esm copy std-esm-package.json to package.json and the same in the esm-module folder/package

uncomment the lines in index.js

import { cjsDotExport as cjs } from 'example-cjs-module'
cjs()

delete /node_modules and run npm-install

then npm start

the output will be

Hello from esm module
Hello from cjs module

Conclusion

the std/esm support can import cjs dot exports as named imports just fine but core esm v14 support cannot.