Generate UMD build with Rollup

[Rich-Harris]

This PR generates a UMD build with Rollup, per @gaearon's suggestion on #928. The goal is to produce more compact, readable output.

It doesn't change the build:lib task, as Rollup only bundles modules rather than doing 1:1 transpilation, but I could amend the PR to create a CommonJS bundle in lib if that's desirable.

Zipped size is 14.5% smaller than the current build:

	Unminified	Minified	Gzipped
Current	21643	5402	1904
With Rollup	16177	3978	1628

[timdorr]

@gaearon What do you think about this? One of the nice side benefits is a more readable UMD output, and a removal of the ugly Webpack bootstrap code. The tradeoff being you now have two build tools in the same project. But for the UMD end user, it's a win.

[gaearon]

@timdorr

I want to wait for Lodash 4 to come out and then revisit, per #928 (comment)

[tracker1]

how about process.argv.indexOf('--prod') >= 0, then it can be on any argument.

[thisconnect]

I'd love to use redux in a project where we rollup everything. As far as I know, it is not possible to rollup an application that imports redux, neither with redux's main, jsnext:main nor the dist/redux.js. :(
umd or es6 would let us use redux. hope this gets merged.

[gaearon]

Redux has UMD build in dist folder.

[gaearon]

I'd love to use redux in a project where we rollup everything. As far as I know, it is not possible to rollup an application that imports redux, neither with redux's main, jsnext:main nor the dist/redux.js. :(

Can you please explain why Redux currently cannot be used with Rollup?

[thisconnect]

@gaearon Hi, sorry for my delay. I finally succeeded building a simple redux example (yes!!!) using some of @Rich-Harris PR's ideas. The main issue that it did not work in the first place was that I was missing replace({ 'process.env.NODE_ENV': JSON.stringify('production') }).
It did build but error'd in the browser Uncaught ReferenceError: process is not defined. With "replace process" stuff all works fine!

I setup a gist with 2 builds, one using es6 import and one commonjs require. Download npm i && npm start then open the html in a browser. Note: the minified version of es6 import has about half the size of the one built from commonjs with requires and no jsnext.

https://gist.github.com/thisconnect/af9c83ed56e9d554f63b

Thanks btw for the video's I love them! :)

[simplesmiler]

@gaearon jsnext:main of redux points to the es6 code, which breaks rolling up (this can be worked around with plugins). I believe the consensus is to point jsnext:main to the transpiled code with only imports/exports left intact.
Reference: rollup/rollup#337 (comment)

---

EDIT: #1042

[gaearon]

@simplesmiler

I'm happy to fix it but I can't figure out how to create a Rollup project reproducing the issue with Redux. Can you help me by pointing me at one?

[TrySound]

@gaearon via cli rollup --config rollup.config.js

import npm from 'rollup-plugin-npm';

export default {
  entry: 'src/index.js',
  dest: 'dist/index.js',
  format: 'iife',
  plugins: [
    npm({ jsnext: true })
  ]
};

[Rich-Harris]

The best way I've found to use Redux with Rollup is by building it separately: https://github.com/Rich-Harris/rollup-redux-debug. Lil' bit hacky but it works, and is very space-efficient! #1042 would render the custom build unnecessary.

[thisconnect]

Thanks, looks great! Updated gist to use Redux 3.3.1 and removed commonjs plugin.

main.iife.min.js shrank from 2,972 bytes (with Redux 3.2.1) to 2,202 bytes (with Redux 3.3.1)

[gaearon]

I’m still up for adding this, but it currently doesn’t merge cleanly.
Lodash 4 is out so seems like the only thing blocking this is now fixed.
If you’d like, please rebase and I’ll gladly reopen and merge.