How to indicate that a loader uses ES modules

[morganney]

How do you indicate via config or options that a loader should be loaded using import instead of require?

How do you get this logic to kick-in?

I have a loader that is written with ES modules, and my package.json specifies "type": "module". I am running Jest using the node option --experimental-vm-modules and my tests written with ES modules are all working fine except for this one which has the following error: NonErrorEmittedError: (Emitted value instead of an instance of Error) Error: Must use import to load ES Module.

Relevant stack trace:

      at processResult (node_modules/webpack/lib/NormalModule.js:718:12)
      at node_modules/webpack/lib/NormalModule.js:827:5
      at node_modules/loader-runner/lib/LoaderRunner.js:399:11
      at node_modules/loader-runner/lib/LoaderRunner.js:185:11
      at loadLoader (node_modules/loader-runner/lib/loadLoader.js:33:11)
      at iteratePitchingLoaders (node_modules/loader-runner/lib/LoaderRunner.js:182:2)
      at runLoaders (node_modules/loader-runner/lib/LoaderRunner.js:397:2)
      at NormalModule.doBuild (node_modules/webpack/lib/NormalModule.js:781:3)
      at NormalModule.build (node_modules/webpack/lib/NormalModule.js:928:15)

[morganney]

Looks like the loader must use the .mjs file extension: https://github.com/webpack/loader-runner/blob/master/test/runLoaders.js#L616

Ok, so it is not possible yet: 4f91458#r40502100

[IdeaHunter]

@sokra Hi!
You mentioned in discussion here that this is not possible with webpack yet. Can you please elaborate why and what possibly should be done to change that?

[alexander-akait]

webpack/webpack#13233