rubocop how do you fix Missing magic comment

Question

I have a library of ruby code, and to look for defects I run

$ rubocop

And I get

$ rubocop
Inspecting 153 files
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCWCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCWCCCCCCCWWCCCCC

Offenses:

Gemfile:1:1: C: Missing magic comment # frozen_string_literal: true.
source "https://rubygems.org"

What modifications are required in my Gemfile to make rubocop not complain?

Answer 1

If you want to ignore it, add to your .rubocop.yml

Style/FrozenStringLiteralComment:
  Enabled: false

But may be you want to know what "Magic comment" is, especially if you're using Ruby 2.x

Answer 2

Just add

# frozen_string_literal: true

to the first line of each Ruby file. Or run

rubocop -a

to allow Rubocop to fix all offenses automatically that it is able to fix.

Btw. I like Rubocop and use it myself, but I wouldn't call the things it finds defects. I see the list more like suggestions or reasons for a discussion with my co-workers.