feat: better esm support

[ivanhofer]

fixes #1267

I have investigated #1267 a bit. There are a few road blocks to make msw/node work in a .mjs file:

• [x] reference lib/index.js instead of 'lib' in a few files (easy to achive)
• [x] ~tsup does not support import assertions (needed here https://github.com/mswjs/msw/blob/main/src/context/status.ts#L1) https://github.com/egoist/tsup/issues/714~ workaround: https://github.com/mswjs/msw/pull/1399#discussion_r968360168
• [x] ~dynamic import of node-fetch (https://github.com/mswjs/msw/blob/main/src/context/fetch.ts#L6) is not supported in esm context. https://github.com/evanw/esbuild/issues/1921~ workaround: https://github.com/mswjs/msw/pull/1399#issuecomment-1243681143

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[mattcosta7]

dynamic import of node-fetch

I think we could get around this with something like

useFetch = isNodeProcess() ? (input, init) => import('node-fetch').then(({default: nodeFetch}) => fetch(input, init)) : window.fetch

I'm curious if we could also avoid using node-fetch directly in this library and just stipulate that globalThis.fetch be defined already (via a user polyfill) instead?

[ivanhofer]

With this branch it is now poosible to run the following esm file:

test.mjs

import { setupServer } from 'msw/node'

setupServer()

with the command

node ./test.mjs

[filipw01]

Nice, work. I was about to open an issue, but it looks like it should be fixed once this PR is merged 😄

[ivanhofer]

I think this PR is ready to be merged. Or is something still missing?

[mataspetrikas]

@kettanaito @ivanhofer is this coming into the next release?

[kettanaito]

The only thing I'd add is an automated test for the distributed ESM format. Let me see if I can dig out the previous test I've written...

[kettanaito]

Released: v0.48.0 🎉

This has been released in v0.48.0!

• 📄 Release notes
• 📦 npm package

Make sure to always update to the latest version (npm i msw@latest) to get the newest features and bug fixes.

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