10.0.0-alpha.0: preact/debug doesn't automatically get removed in production

In Preact 8, the whole preact/debug was wrapped in a process.env.NODE_ENV conditional, so it got stripped out of production bundles by default: https://github.com/developit/preact/blob/8/debug/index.js#L3

But in Preact X, when using the .mjs bundle, it will always include the import{checkPropTypes as n}from"prop-types"; line, which in turn will always import the prop-types package. This can be seen in the preact/debug/dist/debug.mjs file. For example here on unpkg: https://unpkg.com/preact@10.0.0-alpha.0/debug/dist/debug.mjs

So now I wrapped preact/debug in my app myself:

if (process.env.NODE_ENV === 'development') {
  require('preact/debug')
}

which is okay, I guess, but the previous behaviour was definitely nicer, and by upgrading to Preact X users could potentially start shipping the debug package to production.

[developit]

We may want to consider only shipping CommonJS and UMD versions of debug for this reason, and using inline requires:

if (process.env.NODE_ENV==='development') {
  require('./debug').initDebug();
  require('./devtools').initDevTools();
}

[JoviDeCroock]

This is documented here and is a side-effect of how ESM works, we can’t really conditionally import in our bundle (async imports on your side however are an option but not in libraries).