Support Tree Shaking through the module field in package.json

[jwickens]

Webpack and rollup use the module field in the package.json to find a build with ES6 imports which enables tree shaking.

You can use babel to transpile with

{
  "presets": [["es2015", {"modules": false}]]
}

You will have configure babel to transpile flow too.

Enabling this in this library could potentially reduce client builds by around 100kb

[wincent]

Thanks for posting this issue, @jwickens. I thought we already had one to track this, but I can't find it. I must have been thinking of this one on the Relay repo.

[baer]

@wincent PR #880 is a step in this direction since it allows for variable output types. After that is merged, implementing this should just be using the BABEL_ENV variable to create different build targets. I'm more than happy to take on this work.

[baer]

Okay, now that #880 is merged, this should be somewhat straightforward! The holdup is that there is a unique build/deploy process that will have to change to support it.

@leebyron @wincent I spent a minute looking through how this gets all bundled up, and it seems like the build steps in the package.json are never used. I don't see any references to dist in the code. Instead, there are a couple of bash scripts here and here that build the project.

Would you mind if I consolidate the duplicate sed and babel commands and use npm scripts to get this tidied up? I'm not sure I see how to do a secondary "modules" build with babel running in the root like it is now.

[baer]

Okay, I've got a first pass at what this type of change would look like. Before I get it all tucked in, I'd love to get some feedback.

#939

[leebyron]

Supported in master (thanks to @baer's hard work) and will be included with the next release