metro.config.js

const fs = require("fs");
const path = require("path");
const getDevPaths = require("get-dev-paths");

const projectRoot = __dirname;
module.exports = {
  resolver: {
    extraNodeModules: {
      react: path.resolve(__dirname, "node_modules/react"),
      "react-native": path.resolve(__dirname, "node_modules/react-native")
    }
  },
  // Old way
  getProjectRoots: () =>
    Array.from(new Set(getDevPaths(projectRoot).map($ => fs.realpathSync($)))),
  // New way
  watchFolders: Array.from(
    new Set(getDevPaths(projectRoot).map($ => fs.realpathSync($)))
  )
};