Use external @babel/runtime helpers

[realityking]

Fixes #302

It does complicate the rollup config quite a bit but this is needed to correctly generate both the ESM and CJS versions.

[trotzig]

Do you know if this increases the size of the built javascript file?

[realityking]

Do you mean the bundled file including the Babel helpers? It will probably depend on how things are build. If other libraries or the application itself uses @babel/runtime it'll be smaller, if the build pipeline is set-up for ESM and concatenating modules (web pack 4 or 5) it should be at worst the same. If it's set-up for CommonJS and there's no deduplication it will be a bit bigger because every module is wrapped.

I'll try to get some data on this :)

[realityking]

To get an idea of the size impact, I created a couple of different builds of the performance tests. This is using Webpack 4, I'd expect better results with Webpack 5 or Rollup.

• Current setup (build of src): 144K
• ESM build with external helpers: 144K
• CJS build with external helper: 148K
• ESM build without external helpers: 144K
• CJS build without external helper: 148K

Conclusion: CJS sucks but no impact on externalising these helpers :)

[realityking]

@trotzig I think a release needs to be done to address #347. It'd be great if you could take a look if you're comfortable including this in that release, if not, please go ahead without this one.

[lencioni]

I think this means that we probably want to remove the production section of the .babelrc. I can do that separately.

[lencioni]

Although don't we want to change this to runtime instead of using the getBabelOutputPlugin method? I'll try out an alternative approach now.

[lencioni]

#353

[lencioni]

I did this slightly differently here #353

Thanks for opening this PR!

[realityking]

That approach is entirely fair as well. :) The different is really one of personal preference as I don't like complicated .babelrc files 😆

Thanks for getting this merged!