Add a DisableComment Cop

Co-authored-by: Issy Long <issyl0@github.com>

Library/Homebrew/rubocops/all.rb

@@ -5,6 +5,7 @@ require_relative "../extend/array"
 require_relative "../extend/blank"
 require_relative "blank"
 require_relative "compact_blank"
+require_relative "disable_comment"
 require_relative "extend/mutable_constant_exclude_unfreezable"
 require_relative "io_read"
 require_relative "move_to_extend_os"

Library/Homebrew/rubocops/disable_comment.rb

@@ -0,0 +1,35 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Checks if rubocop disable comments have a clarifying comment preceding them.
+    class DisableComment < Base
+      MSG = "Add a clarifying comment to the RuboCop disable comment"
+
+      sig { void }
+      def on_new_investigation
+        super
+
+        processed_source.comments.each do |comment|
+          next unless disable_comment?(comment)
+          next if comment?(processed_source[comment.loc.line - 2])
+
+          add_offense(comment)
+        end
+      end
+
+      private
+
+      sig { params(comment: Parser::Source::Comment).returns(T::Boolean)
+      def disable_comment?(comment)
+        comment.text.start_with? "# rubocop:disable"
+      end
+
+sig { params(line: String).returns(T::Boolean) } 
+      def comment?(line)
+        line.strip.start_with? "#"
+      end
+    end
+  end
+end

Library/Homebrew/test/rubocops/disable_comment_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require "rubocops/disable_comment"
+
+RSpec.describe RuboCop::Cop::DisableComment, :config do
+  shared_examples "offense" do |source, correction, message|
+    it "registers an offense and corrects" do
+      expect_offense(<<~RUBY, source:, message:)
+        #{source}
+        ^{source} #{message}
+      RUBY
+
+      expect_correction(<<~RUBY)
+        #{correction}
+      RUBY
+    end
+  end
+
+  it "registers an offense" do
+    expect_offense(<<~RUBY)
+      def something; end
+      # rubocop:disable Naming/AccessorMethodName
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Add a clarifying comment to the RuboCop disable comment
+      def get_decrypted_io; end
+    RUBY
+  end
+
+  it "doesn't register an offense" do
+    expect_no_offenses(<<~RUBY)
+      def something; end
+      # This is a upstream name that we cannot change.
+      # rubocop:disable Naming/AccessorMethodName
+      def get_decrypted_io; end
+    RUBY
+  end
+end