What's the correct way to create a library that works in a monorepo, has an example app, and exposes its App.cpp file?

[shirakaba]

I've spent the last week trying out everything I can think of to just develop a library in my monorepo, following the native module setup docs and more. I've:

1. Used react-native-windows-init:
   • … with experimentalNuGetDependency both enabled and disabled
   • … with both app and lib projectTypes
2. Forked React Native Document Picker
3. Forked @react-native-web-apis/web-storage
4. Forked react-native-randombytes
5. Forked react-native-svg
6. Forked test-app
7. Forked the react-native-test-app example
8. Gave up on building an example app and tried just consuming the native module directly from my main app
9. Gave up on building the libraries inside the monorepo and tried working on packages in a regular repo instead.

For one reason or another, I've not been able to get any of these working. It's genuinely quite exhausting as the builds take forever and the errors are impenetrable.

My environment:

• I'm running on an ARM Mac through an ARM Windows VM, building for ARM.
• I'm using a pnpm monorepo.
• I'm targeting react-native-windows v0.73 to align with react-native-macos.

Reasons for failed attempts include:

• Projects turn out to be library-only, so lack boilerplate for an example app.
• react-native-test-app projects don't expose the App.cpp file (this is a hard requirement, because my native module involves deeplinking).
• The windows folder is empty and running the commands provided in the boilerplate doesn't populate it
• The .sln file keeps being generated with the wrong paths to files, due to working in a monorepo that hoists dependencies.
• The project initialisation fails when using an org prefix.
• The conversion of project name to camel-case in one tool (e.g. ReactNativeAppAuthJS -> ReactNativeAppAuthJs) breaks other downstream tools that neglect to do the same conversion, so the .sln file can't be found.
• I get Command failed with error MSBuildError: C:\Users\jamie\git\my_monorepo\apps\noman\node_modules\react-native-app-auth-js\windows\Generated Files\ReactPackageProvider.g.cpp(5,49): error C2039: 'ReactNativeAppAuthJs': is not a member of 'winrt' (when forking @react-native-web-apis/web-storage).
• Not building for ARM (when using react-native-windows-init --projectType=app --experimentalNuGetDependency).
• Ending up with two copies of hermes.dll (when using react-native-windows-init --projectType=app).

I'd love to get involved with contributing Windows support to React Native packages, but I can't even start the first step. Is there any foolproof workflow for simply creating a native module, with an example app, which exposes its App.cpp file, in a pnpm monorepo?

[shirakaba]

Note to self – although I had no luck with react-native-windows-init, I still need to try out the newer npx react-native init-windows command as suggested here: #13558 (comment)

[chiaramooney]

Tagging @jonthysell who worked on newer init command. Jon, do you have input on this?

[chrisglein]

Linking related issue there: #13559

Summary is that this is pretty far off of our golden path (and will have lower priority as we focus on improving the golden path for the new architecture). That doesn't mean this will be impossible, but there are going to be rough edges and individual issues that need to be resolved one by one. We'll track those as issues logged on the repo.