Add new Rails/MultipleRoutePaths cop

This PR adds new `Rails/MultipleRoutePaths` cop that
checks if mapping a route with multiple paths is deprecated and will be removed in Rails 8.1.

```ruby
# bad
get '/users', '/other_path', to: 'users#index'

# good
get '/users', to: 'users#index'
get '/other_path', to: 'users#index'
```

This provides a migration path for the following warning added in rails/rails#52409.

```consle
DEPRECATION WARNING: Mapping a route with multiple paths is deprecated and will be removed in Rails 8.1.
Please use multiple method calls instead. ...
```

changelog/new_add_new_rails_multiple_route_paths_cop.md

@@ -0,0 +1 @@
+* [#1407](https://github.com/rubocop/rubocop-rails/pull/1407): Add new `Rails/MultipleRoutePaths` cop. ([@koic][])

config/default.yml

@@ -698,6 +698,12 @@ Rails/MigrationClassName:
   Include:
     - db/**/*.rb
 
+Rails/MultipleRoutePaths:
+  Description: 'Checks if mapping a route with multiple paths is deprecated and will be removed in Rails 8.1.'
+  Enabled: pending
+  Severity: warning
+  VersionAdded: '<<next>>'
+
 Rails/NegateInclude:
   Description: 'Prefer `collection.exclude?(obj)` over `!collection.include?(obj)`.'
   StyleGuide: 'https://rails.rubystyle.guide#exclude'

lib/rubocop/cop/mixin/routes_helper.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Common functionality for cops working with routes.
+    module RoutesHelper
+      extend NodePattern::Macros
+
+      HTTP_METHODS = %i[get post put patch delete].freeze
+
+      def_node_matcher :routes_draw?, <<~PATTERN
+        (send (send _ :routes) :draw)
+      PATTERN
+
+      def within_routes?(node)
+        node.each_ancestor(:block).any? { |block| routes_draw?(block.send_node) }
+      end
+    end
+  end
+end

lib/rubocop/cop/rails/match_route.rb

@@ -21,11 +21,11 @@ module Rails
       #   match 'photos/:id', to: 'photos#show', via: :all
       #
       class MatchRoute < Base
+        include RoutesHelper
         extend AutoCorrector
 
         MSG = 'Use `%<http_method>s` instead of `match` to define a route.'
         RESTRICT_ON_SEND = %i[match].freeze
-        HTTP_METHODS = %i[get post put patch delete].freeze
 
         def_node_matcher :match_method_call?, <<~PATTERN
           (send nil? :match $_ $(hash ...) ?)
@@ -60,14 +60,6 @@ def register_offense(node, http_method)
           end
         end
 
-        def_node_matcher :routes_draw?, <<~PATTERN
-          (send (send _ :routes) :draw)
-        PATTERN
-
-        def within_routes?(node)
-          node.each_ancestor(:block).any? { |a| routes_draw?(a.send_node) }
-        end
-
         def extract_via(node)
           via_pair = via_pair(node)
           return %i[get] unless via_pair

lib/rubocop/cop/rails/multiple_route_paths.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # Checks if mapping a route with multiple paths is deprecated and will be removed in Rails 8.1.
+      #
+      # @example
+      #
+      #   # bad
+      #   get '/users', '/other_path', to: 'users#index'
+      #
+      #   # good
+      #   get '/users', to: 'users#index'
+      #   get '/other_path', to: 'users#index'
+      #
+      class MultipleRoutePaths < Base
+        include RoutesHelper
+        extend AutoCorrector
+
+        MSG = 'Use separate routes instead of combining multiple route paths in a single route.'
+        RESTRICT_ON_SEND = HTTP_METHODS
+
+        IGNORED_ARGUMENT_TYPES = %i[array hash].freeze
+
+        def on_send(node)
+          return unless within_routes?(node)
+
+          route_paths = node.arguments.reject { |argument| IGNORED_ARGUMENT_TYPES.include?(argument.type) }
+          return if route_paths.count < 2
+
+          add_offense(node) do |corrector|
+            corrector.replace(node, migrate_to_multiple_routes(node, route_paths))
+          end
+        end
+
+        private
+
+        def migrate_to_multiple_routes(node, route_paths)
+          rest = route_paths.last.source_range.end.join(node.source_range.end).source
+          indentation = ' ' * node.source_range.column
+
+          route_paths.map do |route_path|
+            "#{node.method_name} #{route_path.source}#{rest}"
+          end.join("\n#{indentation}")
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -7,6 +7,7 @@
 require_relative 'mixin/enforce_superclass'
 require_relative 'mixin/index_method'
 require_relative 'mixin/migrations_helper'
+require_relative 'mixin/routes_helper'
 require_relative 'mixin/target_rails_version'
 
 require_relative 'rails/action_controller_flash_before_render'
@@ -77,6 +78,7 @@
 require_relative 'rails/mailer_name'
 require_relative 'rails/match_route'
 require_relative 'rails/migration_class_name'
+require_relative 'rails/multiple_route_paths'
 require_relative 'rails/negate_include'
 require_relative 'rails/not_null_column'
 require_relative 'rails/order_by_id'

spec/rubocop/cop/rails/multiple_route_paths_spec.rb

@@ -0,0 +1,112 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::MultipleRoutePaths, :config do
+  it 'registers an offense when using a route with multiple string route paths' do
+    expect_offense(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', '/other_path/users', '/another_path/users'
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use separate routes instead of combining multiple route paths in a single route.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users'
+        get '/other_path/users'
+        get '/another_path/users'
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using a route with multiple route paths with option' do
+    expect_offense(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', '/other_path/users', '/another_path/users', to: 'users#index'
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use separate routes instead of combining multiple route paths in a single route.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', to: 'users#index'
+        get '/other_path/users', to: 'users#index'
+        get '/another_path/users', to: 'users#index'
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using a route with multiple route paths with splat option' do
+    expect_offense(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', '/other_path/users', '/another_path/users', **options
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use separate routes instead of combining multiple route paths in a single route.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', **options
+        get '/other_path/users', **options
+        get '/another_path/users', **options
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using a route with multiple symbol route paths' do
+    expect_offense(<<~RUBY)
+      Rails.application.routes.draw do
+        get :resend, :generate_new_password
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use separate routes instead of combining multiple route paths in a single route.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      Rails.application.routes.draw do
+        get :resend
+        get :generate_new_password
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using single string path method calls' do
+    expect_no_offenses(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users'
+        get '/other_path/users'
+        get '/another_path/users'
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using single string path with option method calls' do
+    expect_no_offenses(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/users', to: 'users#index'
+        get '/other_path/users', to: 'users#index'
+        get '/another_path/users', to: 'users#index'
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using single string path with array literal' do
+    expect_no_offenses(<<~RUBY)
+      Rails.application.routes.draw do
+        get '/other_path/users', []
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using single route path with no arguments' do
+    expect_no_offenses(<<~RUBY)
+      Rails.application.routes.draw do
+        get
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when not within routes' do
+    expect_no_offenses(<<~RUBY)
+      get '/users', '/other_path/users', '/another_path/users'
+    RUBY
+  end
+end