Add support for reloading in React Native environment

[rasom]

Currently lein-figwheel >= 0.5.9 crashes with Reload not defined for this platform error message in React Native applications (re-natal). This commit fixes the problem.

[bhauman]

Well it's pretty obvious we are going to have to start moving to an idea of traits rather than going by an environment.

But for now I'd like to have a react-native-env? and a :react-native key returned by host-env?

And then look for the spots that are using (html-env?) as a behavior switch and include react native as needed.

Ideally if you find a spot that is testing for (html-env?) that needs to include react-native then it would be best to create a function that tests for the trait that is being looked for

(defn trait-console? [] (exists? js/console))

(defn trait-console-warn? [] (and (trait-console?) (exists? js/console.warn))

How does that sound?

[bhauman]

Those trait functions would go in the utils.cljs

[rasom]

Thanks, @bhauman, sounds reasonable.

I've just added updates in another commit, let's see if I understand you correctly.

[bhauman]

The only other thing I worry about, is if goog.global.navigator will exist in all environments?

[rasom]

The only other thing I worry about, is if goog.global.navigator will exist in all environments?

You are right, I'm not sure that it exists in all environments

[tiensonqin]

@rasom I got this same problem when using React Native with Exponent exponent-cljs-template, so thanks for your work.

I've tested goog.global.navigator on these 4 environments:

1. html, exists
2. worker, exists
3. node, not exists
4. react-native, exists and goog.global.navigator.product equals to react-native.

https://github.com/facebook/react-native/issues/1331

[rasom]

@tiensonqin, thanks for checking this. I suppose that (commit)

(and (exists? goog/global.navigator)
     (= goog/global.navigator.product "ReactNative")

will be safe in all environments.