Create a devcontainer command

This command boots the application, and generates a Dev Container setup based on the current configuration of the application.

Author: andrewn617

railties/lib/rails/commands/devcontainer/devcontainer_command.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "rails/generators"
+require "rails/generators/rails/devcontainer/devcontainer_generator"
+
+module Rails
+  module Command
+    class DevcontainerCommand < Base # :nodoc:
+      desc "devcontainer", "Generate a Dev Container setup based on current application configuration"
+      def perform(*)
+        boot_application!
+
+        say "Generating Dev Container with the following options:"
+        devcontainer_options.each do |option, value|
+          say "#{option}: #{value}"
+        end
+
+        Rails::Generators::DevcontainerGenerator.new([], devcontainer_options).invoke_all
+      end
+
+      private
+        def devcontainer_options
+          @devcontainer_options ||= {
+            app_name: Rails.application.railtie_name.chomp("_application"),
+            database: !!defined?(ActiveRecord) && ActiveRecord::Base.connection_db_config.adapter,
+            active_storage: !!defined?(ActiveStorage),
+            redis: !!(defined?(ActionCable) || defined?(ActiveJob)),
+            system_test: File.exist?("test/application_system_test_case.rb"),
+            node: File.exist?(".node-version"),
+          }
+        end
+    end
+  end
+end

railties/test/commands/devcontainer_test.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rails/command"
+
+class Rails::Command::DevcontainerTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation
+
+  teardown { teardown_app }
+
+  test "generates devcontainer for default app" do
+    build_app
+
+    output = rails "devcontainer"
+
+    assert_match "app_name: app_template", output
+    assert_match "database: sqlite3", output
+    assert_match "active_storage: true", output
+    assert_match "redis: true", output
+    assert_match "system_test: true", output
+    assert_match "node: false", output
+  end
+end