I can't use a symlinked package

[CodeWhisperer]

Description

Hello everyone, after the new update of react native with version 0.72, and support for Symlink, I wanted to create a small project to test these features, but when importing a package created with lerna for a monorepo, I can't import it and use it correctly.

React Native Version

0.72.1

Output of npx react-native info

info Fetching system and libraries information...
System:
OS: Linux 5.19 Ubuntu 22.04.2 LTS 22.04.2 LTS (Jammy Jellyfish)
CPU: (12) x64 AMD Ryzen 5 5600X 6-Core Processor
Memory: 5.50 GB / 15.54 GB
Shell:
version: 5.1.16
path: /bin/bash
Binaries:
Node:
version: 18.16.1
path: ~/.nvm/versions/node/v18.16.1/bin/node
Yarn:
version: 1.22.19
path: /home/linuxbrew/.linuxbrew/bin/yarn
npm:
version: 9.5.1
path: ~/.nvm/versions/node/v18.16.1/bin/npm
Watchman:
version: 2022.06.20.00
path: /home/linuxbrew/.linuxbrew/bin/watchman
SDKs:
Android SDK: Not Found
IDEs:
Android Studio: Not Found
Languages:
Java:
version: 11.0.19
path: /usr/bin/javac
Ruby:
version: 3.0.2
path: /usr/bin/ruby
npmPackages:
"@react-native-community/cli": Not Found
react:
installed: 18.2.0
wanted: 18.2.0
react-native:
installed: 0.72.1
wanted: 0.72.1
npmGlobalPackages:
"react-native": Not Found
Android:
hermesEnabled: true
newArchEnabled: false
iOS:
hermesEnabled: Not found
newArchEnabled: Not found

Steps to reproduce

First I create an empty folder
mkdir monorepo && cd monorepo

I create a react native app
npx react-native@latest init AwesomeProject

I start lerna
lerna init

I create new package with lerna
lerna create package1

I modify packages/package1/package.js with this code:

import React from 'react';
import { Text, TouchableOpacity } from 'react-native';

export const CustomButton = ({ onPress, title }) => {
  return (
    <TouchableOpacity onPress={onPress}>
      <Text>{title}</Text>
    </TouchableOpacity>
  );
};

I run react native in RN project (still without adding the lerna package)

/monorepo/AwesomeProject$ npm start
/monorepo/AwesomeProject$ npm run android

• The project runs correctly

I install my lerna package
/monorepo/AwesomeProject$ npm install ../packages/package1

I check that it has been installed in package.json

  "dependencies": {
    "package1": "file:../packages/package1",
    "react": "18.2.0",
    "react-native": "0.72.1"
  },

I go to App.tsx and import the package:
import {CustomButton} from 'package1';

And I use it:

  <View>
    <CustomButton
      title="Press me!"
      onPress={() => console.log('Hello!')}
    />
  </View>

Snack, code example, screenshot, or link to a repository

App.spx full code:

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 */

import React from 'react';
import type {PropsWithChildren} from 'react';
import {
  SafeAreaView,
  ScrollView,
  StatusBar,
  StyleSheet,
  Text,
  useColorScheme,
  View,
} from 'react-native';

import {
  Colors,
  DebugInstructions,
  Header,
  LearnMoreLinks,
  ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
import {CustomButton} from 'package1';

type SectionProps = PropsWithChildren<{
  title: string;
}>;

function Section({children, title}: SectionProps): JSX.Element {
  const isDarkMode = useColorScheme() === 'dark';
  return (
    <View style={styles.sectionContainer}>
      <Text
        style={[
          styles.sectionTitle,
          {
            color: isDarkMode ? Colors.white : Colors.black,
          },
        ]}>
        {title}
      </Text>
      <Text
        style={[
          styles.sectionDescription,
          {
            color: isDarkMode ? Colors.light : Colors.dark,
          },
        ]}>
        {children}
      </Text>
    </View>
  );
}

function App(): JSX.Element {
  const isDarkMode = useColorScheme() === 'dark';

  const backgroundStyle = {
    backgroundColor: isDarkMode ? Colors.darker : Colors.lighter,
  };

  return (
    <SafeAreaView style={backgroundStyle}>
      <StatusBar
        barStyle={isDarkMode ? 'light-content' : 'dark-content'}
        backgroundColor={backgroundStyle.backgroundColor}
      />
      <ScrollView
        contentInsetAdjustmentBehavior="automatic"
        style={backgroundStyle}>
        <Header />
        <View
          style={{
            backgroundColor: isDarkMode ? Colors.black : Colors.white,
          }}>
          <Section title="Step One">
            Edit <Text style={styles.highlight}>App.tsx</Text> to change this
            screen and then come back to see your edits.
          </Section>
          <View>
            <CustomButton
              title="Press me!"
              onPress={() => console.log('Hello!')}
            />
          </View>
          <Section title="See Your Changes">
            <ReloadInstructions />
          </Section>
          <Section title="Debug">
            <DebugInstructions />
          </Section>
          <Section title="Learn More">
            Read the docs to discover what to do next:
          </Section>
          <LearnMoreLinks />
        </View>
      </ScrollView>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  sectionContainer: {
    marginTop: 32,
    paddingHorizontal: 24,
  },
  sectionTitle: {
    fontSize: 24,
    fontWeight: '600',
  },
  sectionDescription: {
    marginTop: 8,
    fontSize: 18,
    fontWeight: '400',
  },
  highlight: {
    fontWeight: '700',
  },
});

export default App;

Screen error:

[robhogan]

Hi @CodeWhisperer - in a monorepo setup, Metro should be configured to watch your workspace root. You'll need to make sure that's added to watchFolders in your metro.config.js, for example:

watchFolders: [path.join(__dirname, '..', '..')]

You also need to have symlinks enabled in your Metro config:

resolver: { 
  unstable_enableSymlinks: true
}

If that doesn't work, can you share your metro.config.js?

[CodeWhisperer]

Hello @robhogan , thank you very much for your answer, as you comment, I forgot to add the configuration in metro.config.js, but I have added what you have commented and I still receive the same error.

My metro.config.js

const {getDefaultConfig, mergeConfig} = require('@react-native/metro-config');
const path = require('path');

/**
 * Metro configuration
 * https://facebook.github.io/metro/docs/configuration
 *
 * @type {import('metro-config').MetroConfig}
 */
const config = {
    resolver: {
      unstable_enableSymlinks: true,
      unstable_enablePackageExports: true,
      watchFolders: [path.join(__dirname, '..', '..')],
    },
  };

module.exports = mergeConfig(getDefaultConfig(__dirname), config);

I leave you the folder structure to add more information.

monorepo/
├── AwesomeProject
│   ├── android
│   ├── app.json
│   ├── App.tsx
│   ├── babel.config.js
│   ├── Gemfile
│   ├── index.js
│   ├── ios
│   ├── jest.config.js
│   ├── metro.config.js
│   ├── node_modules
│   ├── package.json
│   ├── package-lock.json
│   ├── README.md
│   ├── __tests__
│   ├── tsconfig.json
│   └── yarn.lock
├── lerna.json
├── package.json
└── packages
    └── package1

If you need more information or any proof, let me know.

[robhogan]

Hi @CodeWhisperer. Looks like the main issue there is that watchFolders needs to be a top-level config option, not under resolver.

Also, if your project structure is <monorepo root>/AwesomeProject/metro.config.js, you probably only want to go up one directory for your watchFolders - the idea is to watch your monorepo/workspace root.

Try this:

const config = {
  watchFolders: [path.resolve(__dirname, '..')],
  resolver: {
    unstable_enableSymlinks: true,
    unstable_enablePackageExports: true,
  },
};

[CodeWhisperer]

Hi @robhogan , Now I have metro.config.js file like this:

const {getDefaultConfig, mergeConfig} = require('@react-native/metro-config');
const path = require('path');

/**
 * Metro configuration
 * https://facebook.github.io/metro/docs/configuration
 *
 * @type {import('metro-config').MetroConfig}
 */
const config = {
    watchFolders: [path.join(__dirname, '..')],
    resolver: {
      unstable_enableSymlinks: true,
      unstable_enablePackageExports: true,
    },
  };

module.exports = mergeConfig(getDefaultConfig(__dirname), config);

And I'm getting this new error

error: Error: Unable to resolve module @babel/runtime/helpers/interopRequireDefault from /home/user/monorepo/packages/package1/lib/package1.js: @babel/runtime/helpers/interopRequireDefault could not be found within the project or in these directories:
  ../../node_modules

I have checked my version of babel and they are these in the package.json:

    "@babel/core": "^7.20.0",
    "@babel/preset-env": "^7.20.0",
    "@babel/runtime": "^7.22.6",

With that configuration, you can run it without problem? could you try it?

[takameyer]

Interesting, I'm hitting this issue as well.

@robhogan
I'll add more context. I'm hosting a react native example in my library's (realm/realm-js) monorepo. I have chosen not to include this example in my npm workspaces, as the amount of custom configuration required for that to work makes upgrading RN versions non-trivial.

In my example, I would like to use npm link to create a symlink to realm. I have applied the following configuration to make this work:

const config = {
  watchFolders: [path.resolve(__dirname, '../../../packages/realm')],
  resolver: {
    unstable_enableSymlinks: true,
  },
};

The symlinks are actually resolving correctly, however it appears with by adding this watchFolders configuration, the local node_modules are no longer being resolved:

Error: Unable to resolve module @babel/runtime/helpers/getPrototypeOf from /******/packages/realm/dist/bundle.react-native.js: @babel/runtime/helpers/getPrototypeOf could not be found within the project or in these directories:
  ../../../packages/realm/node_modules
  ../../../node_modules

It appears to be searching for @babel/runtime/helpers/getPrototypeOf in the configured watch folder and in the root of the monorepo. This babel package is in the current projects node_modules, so I'm unsure why it's not searching for it there.

I have tried setting the rootProject to __dirname and so, but this doesn't seem to work. I have also considered trying out yarn workspaces with no-hoist, but I believe this will not solve the issue, as I am essentially not hoisting the example by not including it as part of my npm workspace.

Any clue here? I can also open a new issue if that helps. I have also tried linking realm from a React Native project outside the mono-repo and ran into the same issue.

[takameyer]

I figured out why this is happening. Since npm workspaces hoists the dependencies of the packages I'm trying to link to the node_modules existing in the root of the mono-repo, metro is not able to determine the location of the deps for the linked package.
I can, however, add the node_modules at the root of the packages to the watchfolders, but there is a mismatch between react versions, so this causes more errors.

[mjvestal]

I ran into issues with symlinks in a monorepo when upgrading from 0.71.* to 0.72.*. This was working previously with rnx-kit and I was unsure what my new metro config should be. I got it working again by keeping my nodeModulesPaths. Without it, metro couldn't find react when resolving a monorepo dependency that also depended on react.

// Find the project and workspace directories
const projectRoot = __dirname
const workspaceRoot = path.resolve(projectRoot, '../..')

const config = {
  resolver: {
    // For monorepo
    unstable_enableSymlinks: true,
    // For monorepo: let Metro know where to resolve packages and in what order
    nodeModulesPaths: [
      path.resolve(projectRoot, 'node_modules'),
      path.resolve(workspaceRoot, 'node_modules'),
    ],
  },
  // For monorepo: Watch all files within the monorepo
  watchFolders: [workspaceRoot],
}

[robhogan]

This is a known problem with a fix in progress - Metro's metro:babel-runtime resolver (#1804) and the React Native preset side (react/react-native#57974). Neither has shipped yet.

Metro injects the @babel/runtime helper imports itself, then resolves them hierarchically from your source file, so they only resolve if @babel/runtime happens to sit on that file's path - which it won't for a package linked in from outside your app. Until the fix lands, adding @babel/runtime as a dependency of the linked package is the most portable workaround.

(NB resolver.unstable_enableSymlinks is obsolete - symlinks are always on since Metro 0.81.)

Leaving this open to track.