False positive for Style/FormatStringToken in Rails validates format #7436
Description
In one of our Rails apps we've a validation that uses the "format" helper to constrain a value to a matching regex, it seems the Style/FormatStringToken cop has incorrectly matched this a use of the format method, which it is not.
Expected behavior
Given an example.rb file with the following content:
class SomeModel < ApplicationRecord
validates :colour, format: { with: /\A#[0-9a-fA-F]{6}\Z/, message: '%{colour} is not a valid hex colour' }
endand running the command
rubocop example.rb --only Style/FormatStringToken
I expect to see no offenses.
Actual behavior
A single Style/FormatStringToken offense is reported
$ rubocop example.rb --only Style/FormatStringToken
Inspecting 1 file
C
Offenses:
example.rb:2:71: C: Style/FormatStringToken: Prefer annotated tokens (like %<foo>s) over template tokens (like %{foo}).
validates :colour, format: { with: /\A#[0-9a-fA-F]{6}\Z/, message: '%{colour} is not a valid hex colour' }
^^^^^^^^^
1 file inspected, 1 offense detected
As an aside, the use of %<colour> in this context is not valid and would produce this error when attempting to save an invalid record:
I18n::MissingInterpolationArgument: missing interpolation argument :colour in "%<colour> is not a valid hex colour"
Steps to reproduce the problem
Covered above in expected behaviour
RuboCop version
$ rubocop -V
0.75.1 (using Parser 2.6.5.0, running on ruby 2.6.5 x86_64-darwin18)