Add pure component transform

[jamiebuilds]

This is all I have time for now so I'm throwing it up into a PR.

Trying to figure out why Jest won't run.

Re: https://twitter.com/cpojer/status/656602748050247680

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[zpao]

FWIW: tests look like they are running for me, but there are a few pre-existing failures

[zpao]

Oh actually I bet it isn't wouldn't be running - add your case in https://github.com/reactjs/react-codemod/blob/master/test/__tests__/transform-tests.js. That won't solve general issues with jest not running but will make sure your test does run when you work that out.

[cpojer]

yeah I'll take a look soon-ish at why the tests are failing.

@thejameskyle awesome work! :)

[cpojer]

This should do a didTransform kinda thing and only return a non-null value if the .size() of this collection is > 0.

See https://github.com/reactjs/react-codemod/blob/master/transforms/pure-render-mixin.js#L172

[cpojer]

This is a good start! The tests should be fixed on master now.

• Maybe take a look at the pure-render-mixin and class transforms in this file for the general structure. I think this codemod should be defensive and only inline actually pure components. It could print a console.warn that says that it skipped a class (class.js has a nice copy-paste-able warning thing).
• Move everything into module.exports to make it actually work
• Maybe add this: https://github.com/reactjs/react-codemod/blob/master/transforms/pure-render-mixin.js#L168 for safety!

[fkling]

It could print a console.warn that says that it skipped a class (class.js has a nice copy-paste-able warning thing).

There is also the stats function. It's basically a keyed counter. If you do a dry run, it prints how often stats was called with that argument. E.g. if a class with more than a render function is encountered, you could call api.stats('complex class') and it would print something like complex class: 4 in the dry run.

Useful for collecting statistics about your codebase / codemod.

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[jamiebuilds]

Threw together a Babel plugin as well. Thought it'd be a useful optimization to run in a production build https://github.com/thejameskyle/babel-plugin-react-pure-components

[cpojer]

this variant should probably take the argument of the ReturnStatement if the length of renderBody.body is one and it only contains a return statement :)

[cpojer]

Yay! Would you mind flattening your commits into a single one before I merge? :)

[cpojer]

Dammit, I missed this because github doesn't notify me about force pushes to PRs.

[jamiebuilds]

Sorry, I knew that, should've pinged you.