Snippets accompanying my article "A concise guide to configuring React Native with Yarn Workspaces" on Medium

metro.config.js

/**
 * Metro Bundler configuration
 * https://facebook.github.io/metro/docs/en/configuration
 *
 * eslint-env node, es6
 */

const exclusionList = require('metro-config/src/defaults/exclusionList');
const getWorkspaces = require('get-yarn-workspaces');
const path = require('path');

function getConfig(appDir, options = {}) {
  const workspaces = getWorkspaces(appDir);

  // Add additional Yarn workspace package roots to the module map
  // https://bit.ly/2LHHTP0
  const watchFolders = [
    path.resolve(appDir, '..', 'node_modules'),
    ...workspaces.filter(
      workspaceDir => !(workspaceDir === appDir),
    ),
  ];

  return {
    watchFolders,
    resolver: {
      blockList: exclusionList([
        // Ignore other resolved react-native installations outside of
        // myapp-native - this prevents a module naming collision when mapped.
        /^((?!myapp-native).)+[\/\\]node_modules[/\\]react-native[/\\].*/,

        // Ignore react-native-svg dependency in myapp-ui, mapped below.
        // react-native-svg must only be included once due to a side-effect. It
        // has not been hoisted as it requires native module linking here.
        // http://bit.ly/2LJ7V4b
        /myapp-ui[\/\\]node_modules[/\\]react-native-svg[/\\].*/,
      ]),
      extraNodeModules: {
        // Resolve all react-native module imports to the locally-installed version
        'react-native': path.resolve(appDir, 'node_modules', 'react-native'),

        // Resolve additional nohoist modules depended on by other packages
        'react-native-svg': path.resolve(
          appDir,
          'node_modules',
          'react-native-svg',
        ),

        // Resolve core-js imports to the locally installed version
        'core-js': path.resolve(appDir, 'node_modules', 'core-js'),
      },
    },
  };
}

module.exports = getConfig(__dirname);

package.json

{
  "name": "myapp-native",
  "version": "1.0.0",
  "private": true,
  "scripts": {
    "postinstall": "jetify",
    "start": "react-native start",
    "android": "react-native run-android",
    "ios": "react-native run-ios",
    "pods": "cd ios; pod install"
  },
  "workspaces": {
    "nohoist": [
      "@react-native-community/async-storage",
      "react-native",
      "react-native/**",
      "react-native-dev-menu",
      "react-native-svg",
      "jetifier"
    ]
  },
  "dependencies": {
    "@react-native-community/async-storage": "^1.6.1",
    "myapp-settings": "1.0.0",
    "myapp-ui": "1.0.0",
    "react": "16.9.0",
    "react-native": "0.61.5",
    "react-native-dev-menu": "^4.0.0",
    "react-native-svg": "^9.12.0"
  },
  "devDependencies": {
    "get-yarn-workspaces": "^1.0.2",
    "metro-config": "^0.56.0"
  }
}

@AdamGerthel That regex looks right to me - another thing you might want to check is whether there is a react-native-svg conflict between app-one/ and app-two/ (your versions), plus whether there is a duplicate react-native-svg installation within dependencies app-one/.

Hopefully you can find from the debug output from what workspace the invariant violation is triggered.

This needs updating for the new metro-config/src/defaults/exclusionList module and the blocklist property in Metro's config.

Thanks for pointing this out @steveluscher, now updated. Funnily enough I now work on Metro 😄