Don't remove all line endings from routes.rb

When there is a single scaffold in the routes.rb with no other lines
then revoking/destroying it will create a routes.rb file with a syntax
error. This is because the sentinel for the Thor `route` action didn't
include the newline but the logged route code did.

The fix is to add the newline to the sentinel and remove it from the
the logged route code.

Fixes #15913.

railties/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Don't remove all line endings from routes.rb when revoking scaffold.
+
+    Fixes #15913.
+
+    *Andrew White*
+
 *   Rename `--skip-test-unit` option to `--skip-test` in app generator
 
     *Melanie Gilman*

railties/lib/rails/generators/actions.rb

@@ -218,10 +218,10 @@ module Rails
       #   route "root 'welcome#index'"
       def route(routing_code)
         log :route, routing_code
-        sentinel = /\.routes\.draw do\s*$/
+        sentinel = /\.routes\.draw do\s*\n/m
 
         in_root do
-          inject_into_file 'config/routes.rb', "\n  #{routing_code}", { after: sentinel, verbose: false }
+          inject_into_file 'config/routes.rb', "  #{routing_code}", { after: sentinel, verbose: false }
         end
       end
 

railties/test/generators/scaffold_generator_test.rb

@@ -245,6 +245,24 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
     assert_file "config/routes.rb", /\.routes\.draw do\s*\|map\|\s*$/
   end
 
+  def test_scaffold_generator_on_revoke_does_not_mutilate_routes
+    run_generator
+
+    route_path = File.expand_path("config/routes.rb", destination_root)
+    content = File.read(route_path)
+
+    # Remove all of the comments and blank lines from the routes file
+    content.gsub!(/^  \#.*\n/, '')
+    content.gsub!(/^\n/, '')
+
+    File.open(route_path, "wb") { |file| file.write(content) }
+    assert_file "config/routes.rb", /\.routes\.draw do\n  resources :product_lines\nend\n\z/
+
+    run_generator ["product_line"], :behavior => :revoke
+
+    assert_file "config/routes.rb", /\.routes\.draw do\nend\n\z/
+  end
+
   def test_scaffold_generator_no_assets_with_switch_no_assets
     run_generator [ "posts", "--no-assets" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"