A Ruby code snippet to check whether an Xcode project and its targets have empty build settings

check_empty_build_settings.rb

require 'xcodeproj'

desc "Errors if the project contains build settings"
task :check_empty_build_settings do
  project = Xcodeproj::Project.open(PROJECT_PATH)
  elements_with_settings = []
  
  # Project
  project
    .build_configurations
    .each do |configuration|
      unless configuration.build_settings.empty?
      	elements_with_settings << "Project[#{configuration.name}]" 
      end
    end
  
  # Targets
  project
    .targets
    .each do |target|
      target.build_configurations.each do |configuration|
        unless configuration.build_settings.empty?
        	elements_with_settings << "#{target.name}[#{configuration.name}]"
        end
      end
    end
  
  unless elements_with_settings.empty?
    message = <<~EOD
    The following elements have build settings defined: #{elements_with_settings.join(", ")}.

    Move those to the associated .xcconfig files.
    EOD
    abort(message)
  else
    puts "The project and its targets have no build settings."
  end
end