React Native: crypto module problem

Crypto dependency problem

on React Native

Having upgraded to React Native 0.65.1, I now get the following error when building the app:

error: Error: Unable to resolve module crypto from /path/project/node_modules/@walletconnect/randombytes/dist/cjs/node/index.js: crypto could not be found within the project or in these directories:
  node_modules

If you are sure the module exists, try these steps:
 1. Clear watchman watches: watchman watch-del-all
 2. Delete node_modules and run yarn install
 3. Reset Metro's cache: yarn start --reset-cache
 4. Remove the cache: rm -rf /tmp/metro-*
   5 | Object.defineProperty(exports, "__esModule", { value: true });
   6 | exports.randomBytes = void 0;
>  7 | const crypto_1 = __importDefault(require("crypto"));
     |                                           ^
   8 | const encoding_1 = require("@walletconnect/encoding");
   9 | function randomBytes(length) {
  10 |     const buf = crypto_1.default.randomBytes(length);

Some discussion about this on stackoverflow: https://stackoverflow.com/a/64363788

[ziadTaha]

following the workflow from react-native-crypto https://github.com/tradle/react-native-crypto

npm i --save react-native-crypto

install peer deps

npm i --save react-native-randombytes react-native link react-native-randombytes

on RN >= 0.60, instead do: cd iOS && pod install

install latest rn-nodeify

npm i --save-dev rn-nodeify

install node core shims and recursively hack package.json files in ./node_modules to add/update the “browser”/“react-native” field with relevant mappings

./node_modules/.bin/rn-nodeify --hack --install

it should work fine

[benorgera]

This is the issue of react native running in browser environment, not having the Node.js builtin deps. See here or here. To fix:

npm i --save-dev rn-nodeify

Add postinstall script to nodemodules:

"scripts": {
  …
  "postinstall": "node_modules/.bin/rn-nodeify --install crypto --hack"
}

Then npm install.

Note if you have this issue with multiple Node.js builtin packages (ie. streams) you can hack them inline as

"postinstall": "node_modules/.bin/rn-nodeify --install crypto --hack && node_modules/.bin/rn-nodeify --install stream --hack"