RakeTask options for formatter don't remove default

[tigris]

If you set a formatter in the rake task like below, the "default" formatter isn't removed from the formatter set, and you end up with both formatters. As such there is no way to set a "default" formatter via rake.

RuboCop::RakeTask.new(:rubocop) do |t|
  t.options = %w(--format json)
end

[jonas054]

There's a special attribute for rake tasks called formatters that you should use instead of options. See https://github.com/bbatsov/rubocop#rake-integration

[tigris]

You're right. This works as expected. I wonder if the above still sounds like a "bug". Completely up to you, happy to just close it if you want.

[jonas054]

I think we should issue a warning if -f/--format appears in t.options, so please leave this open.