Generate a .devcontainer folder and its contents when creating a new app.

The .devcontainer folder includes everything needed to boot the app and do development in a remote container.

The container setup includes:
 - A redis container for Kredis, ActionCable etc.
 - A database (SQLite, Postgres, MySQL or MariaDB)
 - A Headless chrome container for system tests
 - Active Storage configured to use the local disk and with preview features working

If any of these options are skipped in the app setup they will not be included in the container configuration.

These files can be skipped using the `--no-devcontainer` option.

Co-authored-by: Rafael Mendonça França <[email protected]>

Author: andrewn617

actionpack/lib/action_dispatch/system_test_case.rb

@@ -161,7 +161,7 @@ def self.driven_by(driver, using: :chrome, screen_size: [1400, 1400], options: {
       self.driver = SystemTesting::Driver.new(driver, **driver_options, &capabilities)
     end
 
-    # Configuration for the System Test application server
+    # Configuration for the System Test application server.
     #
     # By default this is localhost. This method allows the host and port to be specified manually.
     def self.served_by(host:, port:)

railties/CHANGELOG.md

@@ -1,3 +1,19 @@
+*   Generate a .devcontainer folder and its contents when creating a new app.
+
+    The .devcontainer folder includes everything needed to boot the app and do development in a remote container.
+
+    The container setup includes:
+     - A redis container for Kredis, ActionCable etc.
+     - A database (SQLite, Postgres, MySQL or MariaDB)
+     - A Headless chrome container for system tests
+     - Active Storage configured to use the local disk and with preview features working
+
+    If any of these options are skipped in the app setup they will not be included in the container configuration.
+
+    These files can be skipped using the `--skip-devcontainer` option.
+
+    *Andrew Novoselac & Rafael Mendonça França*
+
 *   Introduce `SystemTestCase#served_by` for configuring the System Test application server
 
     By default this is localhost. This method allows the host and port to be specified manually.

railties/lib/rails/generators.rb

@@ -23,6 +23,7 @@ module Generators
     autoload :NamedBase,       "rails/generators/named_base"
     autoload :ResourceHelpers, "rails/generators/resource_helpers"
     autoload :TestCase,        "rails/generators/test_case"
+    autoload :Devcontainer,    "rails/generators/devcontainer"
 
     mattr_accessor :namespace
 

railties/lib/rails/generators/app_base.rb

@@ -13,6 +13,7 @@ module Rails
   module Generators
     class AppBase < Base # :nodoc:
       include Database
+      include Devcontainer
       include AppName
 
       NODE_LTS_VERSION = "18.15.0"
@@ -109,6 +110,9 @@ def self.add_shared_options_for(name)
         class_option :skip_ci,             type: :boolean, default: nil,
                                            desc: "Skip GitHub CI files"
 
+        class_option :skip_devcontainer,   type: :boolean, default: false,
+                                           desc: "Skip devcontainer files"
+
         class_option :dev,                 type: :boolean, default: nil,
                                            desc: "Set up the #{name} with Gemfile pointing to your Rails checkout"
 
@@ -400,6 +404,10 @@ def skip_ci?
         options[:skip_ci]
       end
 
+      def skip_devcontainer?
+        options[:skip_devcontainer]
+      end
+
       class GemfileEntry < Struct.new(:name, :version, :comment, :options, :commented_out)
         def initialize(name, version, comment, options = {}, commented_out = false)
           super

railties/lib/rails/generators/database.rb

@@ -90,6 +90,14 @@ def mysql_socket
             "/opt/lampp/var/mysql/mysql.sock"         # xampp for linux
           ].find { |f| File.exist?(f) } unless Gem.win_platform?
         end
+
+        def mysql_database_host
+          if options[:skip_devcontainer]
+            "localhost"
+          else
+            "<%= ENV.fetch(\"DB_HOST\") { \"localhost\" } %>"
+          end
+        end
     end
   end
 end

railties/lib/rails/generators/devcontainer.rb

@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+module Rails
+  module Generators
+    module Devcontainer
+      private
+        def devcontainer_ruby_version
+          gem_ruby_version.to_s.match(/^\d+\.\d+/).to_s
+        end
+
+        def devcontainer_dependencies
+          return @devcontainer_dependencies if @devcontainer_dependencies
+
+          @devcontainer_dependencies = []
+
+          @devcontainer_dependencies << "selenium" if depends_on_system_test?
+          @devcontainer_dependencies << "redis" if devcontainer_needs_redis?
+          @devcontainer_dependencies << db_name_for_devcontainer if db_name_for_devcontainer
+          @devcontainer_dependencies
+        end
+
+        def devcontainer_variables
+          return @devcontainer_variables if @devcontainer_variables
+
+          @devcontainer_variables = {}
+
+          @devcontainer_variables["CAPYBARA_SERVER_PORT"] = "45678" if depends_on_system_test?
+          @devcontainer_variables["SELENIUM_HOST"] = "selenium" if depends_on_system_test?
+          @devcontainer_variables["REDIS_URL"] = "redis://redis:6379/1" if devcontainer_needs_redis?
+          @devcontainer_variables["DB_HOST"] = db_name_for_devcontainer if db_name_for_devcontainer
+
+          @devcontainer_variables
+        end
+
+        def devcontainer_volumes
+          return @devcontainer_volumes if @devcontainer_volumes
+
+          @devcontainer_volumes = []
+
+          @devcontainer_volumes << "redis-data" if devcontainer_needs_redis?
+          @devcontainer_volumes << db_volume_name_for_devcontainer if db_volume_name_for_devcontainer
+
+          @devcontainer_volumes
+        end
+
+        def devcontainer_needs_redis?
+          !(options.skip_action_cable? && options.skip_active_job?)
+        end
+
+        def db_name_for_devcontainer(database = options[:database])
+          case database
+          when "mysql"          then "mysql"
+          when "trilogy"        then "mariadb"
+          when "postgresql"     then "postgres"
+          end
+        end
+
+        def db_volume_name_for_devcontainer(database = options[:database])
+          case database
+          when "mysql"          then "mysql-data"
+          when "trilogy"        then "mariadb-data"
+          when "postgresql"     then "postgres-data"
+          end
+        end
+
+        def devcontainer_db_service_yaml(**options)
+          return unless service = db_service_for_devcontainer
+
+          service.to_yaml(**options)[4..-1]
+        end
+
+        def db_service_for_devcontainer(database = options[:database])
+          case database
+          when "mysql"          then mysql_service
+          when "trilogy"        then mariadb_service
+          when "postgresql"     then postgres_service
+          end
+        end
+
+        def postgres_service
+          {
+            "postgres" => {
+              "image" => "postgres:16.1",
+              "restart" => "unless-stopped",
+              "networks" => ["default"],
+              "volumes" => ["postgres-data:/var/lib/postgresql/data"],
+              "environment" => {
+                "POSTGRES_USER" => "postgres",
+                "POSTGRES_PASSWORD" => "postgres"
+              }
+            }
+          }
+        end
+
+        def mysql_service
+          {
+            "mysql" => {
+              "image" => "mysql/mysql-server:8.0",
+              "restart" => "unless-stopped",
+              "environment" => {
+                "MYSQL_ALLOW_EMPTY_PASSWORD" => true,
+                "MYSQL_ROOT_HOST" => "%"
+              },
+              "volumes" => ["mysql-data:/var/lib/mysql"],
+              "networks" => ["default"],
+            }
+          }
+        end
+
+        def mariadb_service
+          {
+            "mariadb" => {
+              "image" => "mariadb:10.5",
+              "restart" => "unless-stopped",
+              "networks" => ["dqefault"],
+              "volumes" => ["mariadb-data:/var/lib/mysql"],
+              "environment" => {
+                "MARIADB_ALLOW_EMPTY_ROOT_PASSWORD" => true,
+              },
+            }
+          }
+        end
+
+        def db_service_names
+          ["mysql", "mariadb", "postgres"]
+        end
+    end
+  end
+end

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -266,6 +266,14 @@ def vendor
     def config_target_version
       @config_target_version || Rails::VERSION::STRING.to_f
     end
+
+    def devcontainer
+      empty_directory ".devcontainer"
+
+      template ".devcontainer/devcontainer.json"
+      template ".devcontainer/Dockerfile"
+      template ".devcontainer/compose.yaml"
+    end
   end
 
   module Generators
@@ -455,6 +463,11 @@ def create_storage_files
         build(:storage)
       end
 
+      def create_devcontainer_files
+        return if skip_devcontainer? || options[:dummy_app]
+        build(:devcontainer)
+      end
+
       def delete_app_assets_if_api_option
         if options[:api]
           remove_dir "app/assets"

railties/lib/rails/generators/rails/app/templates/.devcontainer/Dockerfile.tt

@@ -0,0 +1,16 @@
+# Make sure RUBY_VERSION matches the Ruby version in .ruby-version
+ARG RUBY_VERSION=<%= devcontainer_ruby_version %>
+FROM mcr.microsoft.com/devcontainers/ruby:1-$RUBY_VERSION-bookworm
+
+<%- unless options.skip_active_storage -%>
+# Install packages needed to build gems
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y \
+      libvips \
+      #  For video thumbnails
+      ffmpeg \
+      # For pdf thumbnails. If you want to use mupdf instead of poppler,
+      # you can install the following packages instead:
+      # mupdf mupdf-tools
+      poppler-utils
+<%- end -%>

railties/lib/rails/generators/rails/app/templates/.devcontainer/compose.yaml.tt

@@ -0,0 +1,55 @@
+services:
+  rails-app:
+    build:
+      context: ..
+      dockerfile: .devcontainer/Dockerfile
+
+    volumes:
+    - ../..:/workspaces:cached
+
+    # Overrides default command so things don't shut down after the process ends.
+    command: sleep infinity
+
+    networks:
+    - default
+
+    # Uncomment the next line to use a non-root user for all processes.
+    # user: vscode
+
+    # Use "forwardPorts" in **devcontainer.json** to forward an app port locally.
+    # (Adding the "ports" property to this file will not forward from a Codespace.)
+    ports:
+    - 45678:45678
+<%- if !devcontainer_dependencies.empty? -%>
+    depends_on:
+<%- devcontainer_dependencies.each do |dependency| -%>
+    - <%= dependency %>
+<%- end -%>
+<%- end -%>
+
+<%- if depends_on_system_test? -%>
+  selenium:
+    image: seleniarm/standalone-chromium
+    restart: unless-stopped
+    networks:
+    - default
+<%- end -%>
+
+<%- if devcontainer_needs_redis? -%>
+  redis:
+    image: redis:7.2
+    restart: unless-stopped
+    networks:
+    - default
+    volumes:
+    - redis-data:/data
+<%- end -%>
+
+  <%= devcontainer_db_service_yaml(indentation: 4) %>
+
+<%- if !devcontainer_volumes.empty? -%>
+volumes:
+<%- devcontainer_volumes.each do |volume| -%>
+  <%= volume %>:
+<%- end -%>
+<%- end -%>

railties/lib/rails/generators/rails/app/templates/.devcontainer/devcontainer.json.tt

@@ -0,0 +1,34 @@
+// For format details, see https://aka.ms/devcontainer.json. For config options, see the
+// README at: https://github.com/devcontainers/templates/tree/main/src/ruby
+{
+  "name": "<%= app_name %>",
+  "dockerComposeFile": "compose.yaml",
+  "service": "rails-app",
+  "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",
+
+  // Features to add to the dev container. More info: https://containers.dev/features.
+  "features": {
+    "ghcr.io/devcontainers/features/github-cli:1": {}
+  },
+
+<%- if !devcontainer_variables.empty? -%>
+  "containerEnv": {
+    <%= devcontainer_variables.map { |key, value| "\"#{key}\": \"#{value}\"" }.join(",\n    ") %>
+  },
+<%- end -%>
+
+  // Features to add to the dev container. More info: https://containers.dev/features.
+  // "features": {},
+
+  // Use 'forwardPorts' to make a list of ports inside the container available locally.
+  // "forwardPorts": [],
+
+  // Configure tool-specific properties.
+  // "customizations": {},
+
+  // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
+  // "remoteUser": "root",
+
+  // Use 'postCreateCommand' to run commands after the container is created.
+  "postCreateCommand": "bin/setup"
+}