react-native-config standard - Agenda 2023-01-19

[kelset]

Agenda notes

1. Where are we today

   • align-deps Use align-deps to help migrate apps to the New Architecture #1863
     • the problem with new arch: we have no clear way of knowing what works / what doesn't (and not even programmatically)
   • declaring configs today
     • react-native.config.js https://github.com/react-native-community/cli/blob/main/docs/configuration.md#configuration
       • https://github.com/react-native-community/cli/blob/main/docs/projects.md
       • https://github.com/react-native-community/cli/blob/main/docs/dependencies.md
       • https://github.com/react-native-community/cli/blob/main/docs/platforms.md
       • https://github.com/react-native-community/cli/blob/main/docs/plugins.md
       • desktop platforms
         • Provide information to metro to redirect to rn-macos when building macos react-native-macos#587
         • Allow out of tree platforms to work without custom metro configs react-native-community/cli#1115
         • https://microsoft.github.io/react-native-windows/docs/config
     • Expo's apps app.json/ app.config.js https://docs.expo.dev/workflow/configuration/
       • https://docs.expo.dev/versions/latest/config/app/
       • Q: is app.json used in non Expo-projects? RNTA?
         • Brent in 2020: What is the purpose of app.json file? Is it safe to delete it? react-native-community/cli#1113 (comment)
     • Expo's libs expo-module.config.json (https://docs.expo.dev/modules/autolinking/)
       • https://docs.expo.dev/modules/module-config/
     • react-native-test-app uses app.json https://github.com/microsoft/react-native-test-app/wiki/Manifest-(app.json)
     • codegenConfig
     • react-native core also has some more configuration flags that are hidden in native side (ex. turning on Hermes and the new arch are in iOS's podfile and Android's gradle file)

2. where do we want to be

   • lib maintainers have a way to declare support for the new arch
   • we can use align-deps and rn-directory to surface that information to the developers
     • we need a 3 lights semaphore:
       🔴 = no support for new arch at all
       🟡 = we can infer that it will probably work with the new arch based on. For example, we could use the same one that RNDirectory uses, based on the presence of the codegenConfig field in package.json
       🟢 = library has our custom-setting field set to true

3. How can we get there?

   • proposal 1: define a react-native-config section of package.json that is spec'd and is coherent with existing config approach (should 1:1 having a react-native.config.js/app.config.js) with a dedicated field for declaring new arch support
     • the reason why we need it in the package.json is that it makes it easier/faster to read (especially for rn-directory, no need to download the entire thing)
     • maybe also remove app.json entirely while at it?
   • other proposals?
   • what can we do in the meantime?
     • basic New Arch detection and new status react-native-community/directory#870
     • feat(dep-check): introduce preset with New Arch packages #1877
     • 3rd party libraries - updates and requests reactwg/react-native-new-architecture#6

4. Let's discuss!

   • Expo's proposal
     • doesn't solve the flags for app configuration (ex. hermes, new arch)
     • doesn't mention iOS/Android specificities
   • even the semaphore doesn't cover new arch only / not backward compat case
   • react-native-library section would be a much better name
   • react-native-metadata / react-native-meta is another broader alternative that would allow to keep everything within it and could potentially work along a future also react-native-config
   • reactNativeMeta looks like a winner
     • do we need to version it? (similarly to how CIs do it)
       • codegen changes so we should have a way to tell which version of codegen it's working against
     • let's use more specific keys like TurboModules and/or Fabric?

Action items

• @kelset RFC with first draft of the final idea reactNativeMeta so that we can async fill the details of the specific fields