webpack5 and loaders defined as `.mjs`: enable use of `someloader.mjs` ?

Feature request

What is the expected behavior?

• creating a loader as someloader.cjs or someloader.js works perflectly
• creating the same loader as someloader.mjs throws error (see below

What is motivation or use case for adding/changing the behavior?

• i (and others imo) want to define loaders as mjs

How should this be implemented in your opinion?

• i would need to review webpack internals (and docs, as i could be wrong and theres a bug in my code) before providing an opinion

Are you willing to work on this yourself? yes (with proper support on webpack internals)

example repository where i tried to load someloader.mjs

• clone repo
• $ cd packages/libraries/configproto/webpack
• $ pnpm install
• $ node removeFlowTypesLoader.test.mjs
• see error in terminal

more information

• someloader.cjs that works fine in tap tests
• someloader.cjs converted to .mjs that throws error in tap test
• my copypasta test.compiler.mjs from webpack docs
• line in test file with testconfig for someloader.cjs
• line in test file with testconfig for someloader.mjs
• line in test file for testing bundling with someloader.mjs
• link to issue created in node-tap
• possible related issue https://github.com/webpack/webpack/issues/4072

[alexander-akait]

Please update webpack to the latest version too

[alexander-akait]

Something wrong with tap