[Fix rubocop#841] Fix an error for Rails/ActionOrder

Fixes rubocop#841.

This PR fixes an error for `Rails/ActionOrder`
when using unconventional order of multiple actions.

With this change, autocorrection blank line positions are not as expected,
so they are left to autocorrection of `Layout/EmptyLineBetweenDefs` and
`Layout/EmptyLinesAroundClassBody` cops.

This PR aims to fix the error, that it may be a cleaner autocorrection later.

changelog/fix_an_error_for_rails_action_order.md

@@ -0,0 +1 @@
+* [#841](https://github.com/rubocop/rubocop-rails/issues/841): Fix an error for `Rails/ActionOrder` when using unconventional order of multiple actions. ([@koic][])

lib/rubocop/cop/rails/action_order.rb

@@ -75,8 +75,7 @@ def register_offense(previous, current)
             current = correction_target(current)
             previous = correction_target(previous)
 
-            corrector.replace(current, previous.source)
-            corrector.replace(previous, current.source)
+            swap_range(corrector, current, previous)
           end
         end
 
@@ -106,6 +105,11 @@ def range_with_comments(node)
         def range_with_comments_and_lines(node)
           range_by_whole_lines(range_with_comments(node), include_final_newline: true)
         end
+
+        def swap_range(corrector, range1, range2)
+          corrector.insert_before(range2, range1.source)
+          corrector.remove(range1)
+        end
       end
     end
   end

spec/rubocop/cop/rails/action_order_spec.rb

@@ -18,6 +18,26 @@ def show; end
     RUBY
   end
 
+  it 'detects unconventional order of multiple actions' do
+    expect_offense(<<~RUBY)
+      class UserController < ApplicationController
+        def create; end
+        def edit; end
+        ^^^^^^^^^^^^^ Action `edit` should appear before `create`.
+        def show; end
+        ^^^^^^^^^^^^^ Action `show` should appear before `edit`.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      class UserController < ApplicationController
+        def show; end
+        def edit; end
+        def create; end
+      end
+    RUBY
+  end
+
   it 'supports methods with content' do
     expect_offense(<<~RUBY)
       class UserController < ApplicationController
@@ -33,10 +53,10 @@ def index; end
     expect_correction(<<~RUBY)
       class UserController < ApplicationController
         def index; end
-
         def show
           @user = User.find(params[:id])
         end
+
       end
     RUBY
   end
@@ -137,11 +157,11 @@ class TestController < BaseController
           def index
           end
         end
-
         unless Rails.env.development?
           def edit
           end
         end
+
       end
     RUBY
   end
@@ -181,8 +201,8 @@ def show; end
       expect_correction(<<~RUBY)
         class UserController < ApplicationController
           def show; end
-          def edit; end
           def index; end
+          def edit; end
         end
       RUBY
     end
@@ -205,9 +225,9 @@ def index; end
         class UserController < ApplicationController
           # index
           def index; end
-
           # show
           def show; end
+
         end
       RUBY
     end