Allow stripping of error messages and warnings in production

[agundermann]

Fixes #545

Hope I didn't miss anything ;)

[mjackson]

Thanks @taurose !

I'm trying to think of what the best strategy is here. e.g. the React project uses envify to translate blocks like

if (process.env.NODE_ENV !== 'production') {
  warning( ... );
}

to

if ('development' !== 'production') {
  warning( ... );
}

In this situation, a tool like uglify can come along and strip out the portions of dead code easily, reducing the overall size of the build.

I'd love to take a similar approach in react-router. Do you think you'd be up for it? It would require not only changes to the code, but some tweaks to our build process as well.

[agundermann]

I'm not sure I understand your comment. What you mentioned is already possible with these changes, and scripts/build is able to eliminate the dead code as is. Reported size went from 12943 bytes to 12444.

Since you mentioned build process, I realized only now that facebook has an AST transformation step (https://github.com/facebook/react/blob/master/vendor/constants.js). Is that what you're asking for?

[mjackson]

scripts/build is able to eliminate the dead code as is

Oh, I didn't realize that ;) Thanks for pointing that out. I'll take a closer look.

[agundermann]

Closing this since I think integrating this in the build process would be a better solution.
Feel free to reopen if there's interest after all.