Allow removal of debug code in production builds

[tschaub]

By wrapping debug code in conditions with process.NODE_ENV !== 'production', people using compressors that do dead code removal can generate production builds without the debug code.

This is possible using Browserify with the envify transform before running code through Uglify (with --compress dead_code=true). React itself uses this same pattern.

[hai-cea]

Thanks @tschaub - It may be a good idea to create a utility function to do this? Something like:

Log.warn(...);
Log.error(...);
Log.debug(...);

That way we can keep the NODE_ENV check inside a single function.

[tschaub]

@hai-cea I understand the desire to move the repeated code to utility functions, however I think that might defeat the purpose. The idea here is to keep the warning strings out of production builds. If the implementation of Log.warn has the process.NODE_ENV !== 'production' check, the body of the implementation will be removed, but the call sites (and warning strings) will remain.

Defining a const would be an alternative (e.g. const DEBUG = process.NODE_ENV !== 'production';). But I'm pretty sure this would need to appear in each module where it is used. A build flag is another alternative, but this isn't as widespread a convention as using NODE_ENV.

I understand if these checks seems like a hassle to maintain. And removing the warning strings from production builds is a pretty minor optimization. There would still be some benefit of a utility function that was a no-op in production.

[hai-cea]

Thanks @tschaub - Makes sense to me.

[oliviertassinari]

Why are we using process.NODE_ENV when react is using process.env.NODE_ENV ?

[tschaub]

@oliviertassinari very bad typo. Needs to be fixed.

[oliviertassinari]

@hai-cea @tschaub I have done a new PR to fix it #573

[mmrtnz]

@oliviertassinari's PR has been merged