Fail to build using Xcode 12 Beta 4

Description

When I try to build a project with Xcode 12 Beta 4 to test iOS14, I got a plenty of Undefined symbols for architecture x86_64. Every time I build the app, the list of errors is changed. Native libraries fail to recognize base React classes.

React Native version:

info Fetching system and libraries information...
(node:16978) Warning: Accessing non-existent property 'padLevels' of module exports inside circular dependency
(Use `node --trace-warnings ...` to show where the warning was created)
System:
    OS: macOS 10.15.6
    CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
    Memory: 558.54 MB / 16.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 14.3.0 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.4 - /usr/local/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.9.3 - /Users/laigorols/.rbenv/shims/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 14.0, DriverKit 20.0, macOS 11.0, tvOS 14.0, watchOS 7.0
    Android SDK: Not Found
  IDEs:
    Android Studio: 4.0 AI-193.6911.18.40.6626763
    Xcode: 12.0/12A8179i - /usr/bin/xcodebuild
  Languages:
    Java: 12.0.1 - /usr/bin/javac
    Python: 2.7.16 - /Users/laigorols/.pyenv/shims/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.13.1 => 16.13.1
    react-native: 0.63.2 => 0.63.2
  npmGlobalPackages:
    *react-native*: Not Found

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

1. Add native dependencies to package.json;
2. Install dependencies using yarn install;
3. Run pod install in ios folder to auto link native dependencies;
4. Try to run application in simulator using Xcode;

Expected Results

Application is successfully installed and executed in simulator.

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

Xcode error log: Build Xcode12ReactNativeSample_2020-08-12T17-06-23.txt

Github repository with sample: https://github.com/igoriols/xcode12reactnativesample

[alloy]

Hi all 👋

Unfortunately I only just became aware of this ticket, so my apologies for the delay but thanks for the workarounds and the patience! 🙏

I tried the reproduction kindly provided by @igoriols and was able to determine the problem. The issue is that all the podspecs of these libraries that fail to link depend on the React pod, which is in fact really only an umbrella dependency for pure JS applications to depend on, whereas the native APIs that these libraries rely on actually reside in the React-Core pod.

This means that they technically were always incorrect—conceptually one should always explicitly depend on the lib that provides the APIs you rely on, rather than relying on transitive dependencies—but it seems like in previous Xcode versions the build system worked differently and having the transitive dependencies around just happened to work 🤷‍♂️

The correct fix going forward is for all these libs to update their dependency from React to React-Core:

-  s.dependency 'React'
+  s.dependency 'React-Core'

To unblock yourself you could use something like patch-package to temporarily hot-patch the podspecs you need, but it would be really great for the longer term and the community if you could also submit that change upstream to the respective library 🙏 (See for example this react-native-webview pull-request.)

[xxsnakerxx]

find ./node_modules -type f -name '*.podspec' | xargs sed -i.sed -e "s%'%\"%g"
find ./node_modules -type f -name '*.podspec' | xargs sed -i.sed -e 's%s.dependency[\t ]*"React"%s.dependency "React-Core"%g'