fix: Check Null for RNRandomBytes

[0ndt]

lssues: #40

Expo projects that use the react-native-crypto library have problems with react-native-randombytes.

Uncaught Error:

null is not an object (evaluating 'RNRandomBytes.seed')

means that the RNrandomBytes value is uninitialized. So make sure this value is initialized properly first.

Check Null for RNRandomBytes:

I used if to check if RandomBytes is initialized. This solves the problem with Expo react-native mentioned in issue #40

Testing:

Have been tested on Android simulator, iOS simulator, and Android devices, iOS devices.
_react-native: 0.64
Expo: 44
react-native-crypto: 2.2

[mirceanis]

Shouldn't it be more like this?

Suggested change

	if (RNRandomBytes) {
	if (RNRandomBytes.seed) {
	let seedBuffer = toBuffer(RNRandomBytes.seed)
	addEntropy(seedBuffer)
	} else {
	seedSJCL()
	}
	}
	if (RNRandomBytes && RNRandomBytes.seed) {
	let seedBuffer = toBuffer(RNRandomBytes.seed)
	addEntropy(seedBuffer)
	} else {
	seedSJCL()
	}

[0ndt]

This seems to make the code look clear, right?

[mirceanis]

It's not about clarity, but about the fact that if RNRandomBytes evaluates to false then nothing gets called and in the original code, there's a call to seedSJCL() on the else branch.

[0ndt]

I am quite sure that seedSJCL() will continue to have the lssues #40 , so it is necessary to use the way I used it.

[mirceanis]

You're probably right.. I haven't spent time through the library code, I just landed on this PR as a fix to my current blocker.

[0ndt]

We have solved the problem by patch-package. This is a truly helpful dependency.

[normanzb]

the root question is why RNRandomBytes is not available. it should be there as it is implemented as a native module.
what we found out is when this lib is used as transitive depedency, react-native's cli doesn't do autolinking.
So you need to make sure react-native-randombytes is in your dependency list in package.json file, to be discovered by react native's autolinking. Once that's done you then do again pod install and rebuild the app.

I think whichever the lib that depends on this lib, they need to put this lib into their peerDependency instead.

ref:
react-native-community/cli#1347