Update application_system_test_case.rb from DevcontainerGenerator

Instead of relying on the template to be dev container aware and generate the correct configuration, let's just update the configuration in place when running the DevcontainerGenerator. This will allow the devcontainer command to update this file with the configuration needed for devcontainers without overwriting the entire file.

Author: andrewn617

railties/lib/rails/generators/rails/app/templates/test/application_system_test_case.rb.tt

@@ -1,18 +1,5 @@
 require "test_helper"
 
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
-<% if skip_devcontainer? -%>
   driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ]
-<% else -%>
-  if ENV["CAPYBARA_SERVER_PORT"]
-    served_by host: "rails-app", port: ENV["CAPYBARA_SERVER_PORT"]
-
-    driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ], options: {
-      browser: :remote,
-      url: "http://#{ENV["SELENIUM_HOST"]}:4444"
-    }
-  else
-    driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ]
-  end
-<% end -%>
 end

railties/lib/rails/generators/rails/devcontainer/devcontainer_generator.rb

@@ -34,6 +34,13 @@ def create_devcontainer
         template ".devcontainer/compose.yaml"
       end
 
+      def update_application_system_test_case
+        return unless options[:system_test]
+        return unless File.exist?("test/application_system_test_case.rb")
+
+        gsub_file("test/application_system_test_case.rb", /^(\s*driven_by\b.*)/, system_test_configuration)
+      end
+
       private
         def dependencies
           return @dependencies if @dependencies
@@ -122,6 +129,21 @@ def local_rails_mount
             target: Rails::Generators::RAILS_DEV_PATH
           }
         end
+
+        def system_test_configuration
+          <<~RUBY
+              if ENV["CAPYBARA_SERVER_PORT"]
+                served_by host: "rails-app", port: ENV["CAPYBARA_SERVER_PORT"]
+
+                driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ], options: {
+                  browser: :remote,
+                  url: "http://#{ENV["SELENIUM_HOST"]}:4444"
+                }
+              else
+                driven_by :selenium, using: :headless_chrome, screen_size: [ 1400, 1400 ]
+              end
+          RUBY
+        end
     end
   end
 end

railties/test/generators/app_generator_test.rb

@@ -1285,6 +1285,9 @@ def test_devcontainer
     assert_file(".devcontainer/Dockerfile") do |content|
       assert_match(/ARG RUBY_VERSION=#{RUBY_VERSION}/, content)
     end
+    assert_file("test/application_system_test_case.rb") do |content|
+      assert_match(/served_by host: "rails-app", port: ENV\["CAPYBARA_SERVER_PORT"\]/, content)
+    end
     assert_compose_file do |compose_config|
       assert_equal "my_app", compose_config["name"]