my_abs_path              = "/Users/me/rails_app/config/locales/text_en.yml"
expected_relative_result = "config/locales/text_en.yml"

my_abs_path.delete_prefix("#{Rails.root}/") == expected_relative_result
# => true

# this should be allowed by Rails/FilePath cop because the last / in /Users/me/rails_app/ must be deleted, not just /Users/me/rails_app
my_abs_path.delete_prefix("#{Rails.root}/")

my_abs_path.delete_prefix("#{Rails.root}/")
# raises Rails/FilePath, and is autocorrected to
my_abs_path.delete_prefix("#{Rails.root.join('')}")
# which raises Style/RedundantInterpolation, so we manually correct to
my_abs_path.delete_prefix(Rails.root.join('').to_s)
# which is wrong:
actual = my_abs_path.delete_prefix(Rails.root.join('').to_s)
actual == expected_relative_result
# => false
puts actual
# => "/config/locales/text_en.yml"

# so we try giving an argument to join, but still wrong because Rails.root.join never adds a trailing slash:
actual = my_abs_path.delete_prefix(Rails.root.join('./').to_s)
actual == expected_relative_result
# => false
puts actual
# => "/config/locales/text_en.yml"

# where Rails.root is /Users/me/rails_app
my_abs_path = "/Users/me/rails_app/config/locales/text_en.yml"
expected_relative_result = "config/locales/text_en.yml"

actual = my_abs_path.delete_prefix("#{Rails.root}/")
if actual != expected_relative_result
  raise "Invalid autocorrection: #{actual.inspect} != #{expected_relative_result.inspect}"
end