How to fix Ruby Bundler on Big Sur beta

bundler-fix.md

THE PROBLEM

After updating to macOS Big Sur beta you might encounter issues when using Ruby Bundler to manage Ruby gems in your project - in our case to install CocoaPods and Fastlane for iOS development.

Ignoring json-2.2.0 because its extensions are not built. Try: gem pristine json --version 2.2.0

...

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

...

fatal error: 'ruby/config.h' file not found

THE SOLUTION

1. Make sure you have the latest Xcode and Command line tools installed in a correct directory
2. softwareupdate --all --install --force
3. sudo rm -rf /Library/Developer/CommandLineTools
4. sudo xcode-select --install
5. Install Rbenv to manage Ruby versions

• Why Rbenv is a better choice than RVM: https://dev.to/krtb/why-and-how-i-replaced-rvm-with-rbenv-23ad
• Full Rbenv installation guide: https://github.com/rbenv/rbenv#installation
• brew install rbenv ruby-build
• echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.zshrc
• echo 'if which rbenv > /dev/null; then eval "$(rbenv init -)"; fi' >> ~/.zshrc
• source ~/.zshrc

6. Install Ruby 2.7.2

• rbenv install 2.7.2
• rbenv global 2.7.2
• ruby -v should now return ruby 2.7.2 ...

7. Reinstall CocoaPods and Fastlane

• gem uninstall cocoapods
• rm /usr/local/bin/pod
• gem uninstall fastlane
• rm /usr/local/bin/fastlane
• gem install cocoapods - no sudo
• gem install fastlane - no sudo
• which fastlane and which pod should now return /Users/username/.rbenv/shims/...

8. Profit