Fixup env checks

[Andarist]

Regarding - https://twitter.com/DavidKPiano/status/1098437300550336512 😉

When performing env checks you should never reference process directly - replacing plugins are only concerned with replacing process.env.NODE_ENV lookup. Referencing process causes i.e. webpack to include a polyfill for this object.

Because of that developer-friendly warning which were meant to be removed in production bundles stayed in the bundles.

This has no dramatic effect but it allow bundlers to remove those unwanted strings in production, the UMD bundle went from 10.87 KB to 10.54 KB

In general I don't recommend storing env check result in a variable (inline check is easier for minifiers to remove), and I strongly would advise against exporting it from a file - especially given a fact that you don't flat bundle and depending on the consumer's setup it might not be possible to check this value across module-boundary.

This also provides a browser-friendly build which was actually requested originally ( #227 ) but the fix was done differently. cc @TimvdLippe

[TimvdLippe]

I think this change regresses the case where process is undefined in the browser. E.g. in the browser, you can't have a reference to a variable called process. Therefore, I think this is going to break that use case.

[Andarist]

That's why I'm building ./dist/xstate.esmodules-browsers.js bundle which should be browser compatible (no references to process). It's the same situation as in reduxjs/redux#3143 , redux-saga/redux-saga#1717 , etc

[TimvdLippe]

Ah okay. If that works, good! I am not an expert in rollup, so I don't really understand how it is makes sure it removes the reference. Is it the toplevel: true?

[Andarist]

toplevel: true is for uglify/terser - so it can mangle "top level" variables - otherwise it assumes they might be assigned as globals to window object. I think this actually should be the default for module sources, but maybe logic handling this wasnt implemented yet

I am not an expert in rollup, so I don't really understand how it is makes sure it removes the reference

This is done by rollup-plugin-replace

[Andarist]

@davidkpiano friendly 🏓

[davidkpiano]

Thank you!