helmturner/Expo-bug

Steps to reproduce

1. Create a pnpm workspace with a subdirectory containing an Expo app
2. Follow the manual setup directions for expo-router
3. Follow the directions for setting up a monorepo in the Expo documentation
   • Modify the Metro config:

     // metro.config.js:
     
     const path = require("path");
     const { getDefaultConfig } = require("expo/metro-config");
     
     const projectRoot = __dirname;
     const workspaceRoot = path.resolve(__dirname, "../..");
     
     const config = getDefaultConfig(projectRoot);
     
     config.watchFolders = [workspaceRoot],
     
     config.resolver.nodeModulesPaths = [
       path.resolve(projectRoot, "node_modules"),
       path.resolve(workspaceRoot, "node_modules"),
     ]
     
     module.exports = config;

   • Prepend the run command with EXPO_USE_METRO_WORKSPACE_ROOT=1 as described in Change the default entrypoint

     // package.json:
     
     {
     /* ... */
     "scripts": {
         "ios": "EXPO_USE_METRO_WORKSPACE_ROOT=1 expo run:ios",
         "android": "EXPO_USE_METRO_WORKSPACE_ROOT=1 expo run:android",
         }
     /* ... */
     }

   • Add node-linker=hoisted to .npmrc at the root of the monorepo as described in Can I use another Monorepo tool?

     # .npmrc:
     
     node-linker=hoisted

4. Install expo-dev-client in the Expo app

   cd apps/expo
   pnpm i expo-dev-client

5. run pnpm i in the monorepo root
6. run either pnpm ios or pnpm android to create and launch a development build
7. Open the debugger and observe the error
8. Click any of the links in the error message to see the resolution error

Expected behavior

Source-maps (and by extension, the debugger) should just work.

Actual behavior

The debugger gets a 404 error when trying to load the source-map.

Workaround

Recalling a fix for an older bug, I was able to work around the issue as follows:

• Create an index.ts file in the app's root directory (or index.js, etc)
• Add the following single line:

  import "expo-router/entry";

• Update package.json#main to point to the new file

  {
  "main": "index.ts",
  /* ... */
  }