assetbundle_name.rb

class String
  def snakecase
    #gsub(/::/, '/').
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
    gsub(/([a-z\d])([A-Z])/,'\1_\2').
    tr('-', '_').
    gsub(/\s/, '_').
    gsub(/__+/, '_').
    downcase
  end
  alias_method :underscore, :snakecase
end

Dir.glob('Asset Bundles/*.meta').each do |file_path|
  file = File.read(file_path)
  name = File.basename(file_path).gsub(/.meta/, "").snakecase
  file = file.gsub(/assetBundleName: \n/, "assetBundleName: #{name}\n")
  File.write(file_path, file)
end