Add Rails/ToSWithArgument cop

changelog/new_add_railstoswithargument_cop.md

@@ -0,0 +1 @@
+* [#747](https://github.com/rubocop/rubocop-rails/pull/747): Add `Rails/ToSWithArgument` cop. ([@r7kamura][])

config/default.yml

@@ -952,6 +952,12 @@ Rails/ToFormattedS:
     - to_formatted_s
   VersionAdded: '2.15'
 
+Rails/ToSWithArgument:
+  Description: 'Identifies passing any argument to `#to_s`.'
+  Enabled: pending
+  Safe: false
+  VersionAdded: '<<next>>'
+
 Rails/TransactionExitStatement:
   Description: 'Avoid the usage of `return`, `break` and `throw` in transaction blocks.'
   Enabled: pending

lib/rubocop/cop/rails/to_s_with_argument.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # Identifies passing any argument to `#to_s`.
+      #
+      # @safety
+      #   This cop is marked as unsafe because it may detect `#to_s` calls
+      #   that are not related to Active Support implementation.
+      #
+      # @example
+      #
+      #   # bad
+      #   obj.to_s(:delimited)
+      #
+      #   # good
+      #   obj.to_formatted_s(:delimited)
+      #
+      class ToSWithArgument < Base
+        extend AutoCorrector
+        extend TargetRailsVersion
+
+        MSG = 'Use `to_formatted_s` instead.'
+
+        RESTRICT_ON_SEND = %i[to_s].freeze
+
+        minimum_target_rails_version 7.0
+
+        def on_send(node)
+          return if node.arguments.empty?
+
+          add_offense(node.loc.selector) do |corrector|
+            corrector.replace(node.loc.selector, 'to_formatted_s')
+          end
+        end
+        alias on_csend on_send
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -113,6 +113,7 @@
 require_relative 'rails/time_zone'
 require_relative 'rails/time_zone_assignment'
 require_relative 'rails/to_formatted_s'
+require_relative 'rails/to_s_with_argument'
 require_relative 'rails/transaction_exit_statement'
 require_relative 'rails/uniq_before_pluck'
 require_relative 'rails/unique_validation_without_index'

spec/rubocop/cop/rails/to_s_with_argument_spec.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::ToSWithArgument, :config, :rails70 do
+  context 'without argument' do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        to_s
+      RUBY
+    end
+  end
+
+  context 'with argument' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        to_s(:delimited)
+        ^^^^ Use `to_formatted_s` instead.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        to_formatted_s(:delimited)
+      RUBY
+    end
+  end
+
+  context 'with argument and receiver' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        1.to_s(:delimited)
+          ^^^^ Use `to_formatted_s` instead.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        1.to_formatted_s(:delimited)
+      RUBY
+    end
+  end
+
+  context 'with argument and safe navigation operator' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        1&.to_s(:delimited)
+           ^^^^ Use `to_formatted_s` instead.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        1&.to_formatted_s(:delimited)
+      RUBY
+    end
+  end
+
+  context 'with argument on Rails 6.1', :rails61 do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        to_s
+      RUBY
+    end
+  end
+end