class RuboCop::Cop::Bundler::DuplicatedGem

gem ‘rubocop’, groups: [:development, :test]
# good
end
gem ‘rubocop’
group :development, :test do
# good
end
gem ‘rubocop’
group :test do
end
gem ‘rubocop’
group :development do
# bad
gem ‘rubocop’
gem ‘rubocop’
# bad
@example
A Gem’s requirements should be listed only once in a Gemfile.

def duplicated_gem_nodes 

def duplicated_gem_nodes
  gem_declarations(processed_source.ast)
    .group_by(&:first_argument)
    .values
    .select { |nodes| nodes.size > 1 }
end

def investigate(processed_source) 

def investigate(processed_source)
  return if processed_source.blank?
  duplicated_gem_nodes.each do |nodes|
    nodes[1..-1].each do |node|
      register_offense(
        node,
        node.first_argument.to_a.first,
        nodes.first.first_line
      )
    end
  end
end

def register_offense(node, gem_name, line_of_first_occurrence) 

def register_offense(node, gem_name, line_of_first_occurrence)
  line_range = node.loc.column...node.loc.last_column
  offense_location =
    source_range(processed_source.buffer, node.first_line, line_range)
  message = format(
    MSG,
    gem_name: gem_name,
    line_of_first_occurrence: line_of_first_occurrence
  )
  add_offense(node, location: offense_location, message: message)
end