Refactoring Database generators

Extract all the DB information (gems, dockerfile packages, devcontainer etc.) into an object. This let's us remove the growing number of case statements in this code.

railties/lib/rails/generators/app_base.rb

@@ -12,7 +12,6 @@ require "active_support/core_ext/array/extract_options"
 module Rails
   module Generators
     class AppBase < Base # :nodoc:
-      include Database
       include Devcontainer
       include AppName
 
@@ -40,7 +39,7 @@ module Rails
                                            desc: "Path to some #{name} template (can be a filesystem path or URL)"
 
         class_option :database,            type: :string, aliases: "-d", default: "sqlite3",
-                                           enum: DATABASES,
+                                           enum: Database::DATABASES,
                                            desc: "Preconfigure for selected database"
 
         class_option :skip_git,            type: :boolean, aliases: "-G", default: nil,
@@ -279,7 +278,7 @@ module Rails
       def database_gemfile_entry # :doc:
         return if options[:skip_active_record]
 
-        gem_name, gem_version = gem_for_database
+        gem_name, gem_version = database.gem
         GemfileEntry.version gem_name, gem_version,
           "Use #{options[:database]} as the database for Active Record"
       end
@@ -574,7 +573,7 @@ module Rails
         packages = ["curl"]
 
         # ActiveRecord databases
-        packages << base_package_for_database unless skip_active_record?
+        packages << database.base_package unless skip_active_record?
 
         # ActiveStorage preview support
         packages << "libvips" unless skip_active_storage?
@@ -590,7 +589,7 @@ module Rails
         packages = %w(build-essential git pkg-config)
 
         # add database support
-        packages << build_package_for_database unless skip_active_record?
+        packages << database.build_package unless skip_active_record?
 
         packages << "unzip" if using_bun?
 
@@ -772,6 +771,10 @@ module Rails
 
         directories.sort
       end
+
+      def database
+        @database ||= Database.build(options[:database])
+      end
     end
   end
 end

railties/lib/rails/generators/database.rb

@@ -2,59 +2,84 @@
 
 module Rails
   module Generators
-    module Database # :nodoc:
+    class Database
       DATABASES = %w( mysql trilogy postgresql sqlite3 )
 
-      def gem_for_database(database = options[:database])
+      class << self
-        case database
+        def build(database_name)
-        when "mysql"          then ["mysql2", ["~> 0.5"]]
+          case database_name
-        when "trilogy"        then ["trilogy", ["~> 2.7"]]
+          when "mysql" then MySQL.new
-        when "postgresql"     then ["pg", ["~> 1.1"]]
+          when "postgresql" then PostgreSQL.new
-        when "sqlite3"        then ["sqlite3", [">= 1.4"]]
+          when "trilogy" then MariaDB.new
-        else [database, nil]
+          when "sqlite3" then SQLite3.new
+          else Null.new
+          end
+        end
+
+        def all
+          @all ||= [
+            MySQL.new,
+            PostgreSQL.new,
+            MariaDB.new,
+            SQLite3.new,
+          ]
         end
       end
 
-      def docker_for_database_base(database = options[:database])
+      def name
-        case database
+        raise NotImplementedError
-        when "mysql"          then "curl default-mysql-client libvips"
-        when "trilogy"        then "curl libvips"
-        when "postgresql"     then "curl libvips postgresql-client"
-        when "sqlite3"        then "curl libsqlite3-0 libvips"
-        else nil
-        end
       end
 
-      def docker_for_database_build(database = options[:database])
+      def service
-        case database
+        raise NotImplementedError
-        when "mysql"          then "build-essential default-libmysqlclient-dev git"
-        when "trilogy"        then "build-essential git"
-        when "postgresql"     then "build-essential git libpq-dev"
-        when "sqlite3"        then "build-essential git"
-        else nil
-        end
       end
 
-      def base_package_for_database(database = options[:database])
+      def port
-        case database
+        raise NotImplementedError
-        when "mysql" then "default-mysql-client"
-        when "postgresql" then "postgresql-client"
-        when "sqlite3" then "libsqlite3-0"
-        else nil
-        end
       end
 
-      def build_package_for_database(database = options[:database])
+      def feature_name
-        case database
+        raise NotImplementedError
-        when "mysql" then "default-libmysqlclient-dev"
-        when "postgresql" then "libpq-dev"
-        else nil
-        end
       end
 
-      private
+      def gem
-        def mysql_socket
+        raise NotImplementedError
-          @mysql_socket ||= [
+      end
+
+      def docker_base
+        raise NotImplementedError
+      end
+
+      def docker_build
+        raise NotImplementedError
+      end
+
+      def base_package
+        raise NotImplementedError
+      end
+
+      def build_package
+        raise NotImplementedError
+      end
+
+      def socket; end
+      def host; end
+
+      def feature
+        return unless feature_name
+
+        { feature_name => {} }
+      end
+
+      def volume
+        return unless service
+
+        "#{name}-data"
+      end
+
+      module MySqlSocket
+        def socket
+          @socket ||= [
             "/tmp/mysql.sock",                        # default
             "/var/run/mysqld/mysqld.sock",            # debian/gentoo
             "/var/tmp/mysql.sock",                    # freebsd
@@ -67,13 +92,204 @@ module Rails
           ].find { |f| File.exist?(f) } unless Gem.win_platform?
         end
 
-        def mysql_database_host
+        def host
-          if options[:skip_devcontainer]
+          "localhost"
-            "localhost"
-          else
-            "<%= ENV.fetch(\"DB_HOST\") { \"localhost\" } %>"
-          end
         end
+      end
+
+      class MySQL < Database
+        include MySqlSocket
+
+        def name
+          "mysql"
+        end
+
+        def service
+          {
+            "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 port
+          3306
+        end
+
+        def gem
+          ["mysql2", ["~> 0.5"]]
+        end
+
+        def docker_base
+          "curl default-mysql-client libvips"
+        end
+
+        def docker_build
+          "build-essential default-libmysqlclient-dev git"
+        end
+
+        def base_package
+          "default-mysql-client"
+        end
+
+        def build_package
+          "default-libmysqlclient-dev"
+        end
+
+        def feature_name
+          "ghcr.io/rails/devcontainer/features/mysql-client"
+        end
+      end
+
+      class PostgreSQL < Database
+        def name
+          "postgres"
+        end
+
+        def service
+          {
+            "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 port
+          5432
+        end
+
+        def gem
+          ["pg", ["~> 1.1"]]
+        end
+
+        def docker_base
+          "curl libvips postgresql-client"
+        end
+
+        def docker_build
+          "build-essential git libpq-dev"
+        end
+
+        def base_package
+          "postgresql-client"
+        end
+
+        def build_package
+          "libpq-dev"
+        end
+
+        def feature_name
+          "ghcr.io/rails/devcontainer/features/postgres-client"
+        end
+      end
+
+      class MariaDB < Database
+        include MySqlSocket
+
+        def name
+          "mariadb"
+        end
+
+        def service
+          {
+            "image" => "mariadb:10.5",
+            "restart" => "unless-stopped",
+            "networks" => ["default"],
+            "volumes" => ["mariadb-data:/var/lib/mysql"],
+            "environment" => {
+              "MARIADB_ALLOW_EMPTY_ROOT_PASSWORD" => "true",
+            },
+          }
+        end
+
+        def port
+          3306
+        end
+
+        def gem
+          ["trilogy", ["~> 2.7"]]
+        end
+
+        def docker_base
+          "curl libvips"
+        end
+
+        def docker_build
+          "build-essential git"
+        end
+
+        def base_package
+          nil
+        end
+
+        def build_package
+          nil
+        end
+
+        def feature_name
+          nil
+        end
+      end
+
+      class SQLite3 < Database
+        def name
+          "sqlite3"
+        end
+
+        def service
+          nil
+        end
+
+        def port
+          nil
+        end
+
+        def gem
+          ["sqlite3", [">= 1.4"]]
+        end
+
+        def docker_base
+          "curl libsqlite3-0 libvips"
+        end
+
+        def docker_build
+          "build-essential git"
+        end
+
+        def base_package
+          "libsqlite3-0"
+        end
+
+        def build_package
+          nil
+        end
+
+        def feature_name
+          "ghcr.io/rails/devcontainer/features/sqlite3"
+        end
+      end
+
+      class Null < Database
+        def name; end
+        def service; end
+        def port; end
+        def volume; end
+        def docker_base; end
+        def docker_build; end
+        def base_package; end
+        def build_package; end
+        def feature_name; end
+      end
     end
   end
 end

railties/lib/rails/generators/devcontainer.rb

@@ -3,12 +3,6 @@
 module Rails
   module Generators
     module Devcontainer
-      DB_FEATURES = {
-        "mysql" => "ghcr.io/rails/devcontainer/features/mysql-client",
-        "postgresql" => "ghcr.io/rails/devcontainer/features/postgres-client",
-        "sqlite3" =>  "ghcr.io/rails/devcontainer/features/sqlite3"
-      }
-
       private
         def devcontainer_dependencies
           return @devcontainer_dependencies if @devcontainer_dependencies
@@ -17,7 +11,7 @@ module Rails
 
           @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 << database.name if database.service
           @devcontainer_dependencies
         end
 
@@ -29,7 +23,7 @@ module Rails
           @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["DB_HOST"] = database.name if database.service
 
           @devcontainer_variables
         end
@@ -40,7 +34,7 @@ module Rails
           @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 << database.volume if database.volume
 
           @devcontainer_volumes
         end
@@ -55,7 +49,7 @@ module Rails
           @devcontainer_features["ghcr.io/rails/devcontainer/features/activestorage"] = {} unless options[:skip_active_storage]
           @devcontainer_features["ghcr.io/devcontainers/features/node:1"] = {} if using_node?
 
-          @devcontainer_features.merge!(db_feature_for_devcontainer) if db_feature_for_devcontainer
+          @devcontainer_features.merge!(database.feature) if database.feature
 
           @devcontainer_features
         end
@@ -74,7 +68,7 @@ module Rails
           return @devcontainer_forward_ports if @devcontainer_forward_ports
 
           @devcontainer_forward_ports = [3000]
-          @devcontainer_forward_ports << db_port_for_devcontainer if db_port_for_devcontainer
+          @devcontainer_forward_ports << database.port if database.port
           @devcontainer_forward_ports << 6379 if devcontainer_needs_redis?
 
           @devcontainer_forward_ports
@@ -84,120 +78,10 @@ module Rails
           !(options.skip_action_cable? && options.skip_active_job?)
         end
 
-        def db_port_for_devcontainer(database = options[:database])
-          case database
-          when "mysql", "trilogy" then 3306
-          when "postgresql"       then 5432
-          end
-        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 db_package_for_dockerfile(database = options[:database])
-          case database
-          when "mysql"          then "default-libmysqlclient-dev"
-          when "postgresql"     then "libpq-dev"
-          end
-        end
-
         def devcontainer_db_service_yaml(**options)
-          return unless service = db_service_for_devcontainer
+          return unless service = database.service
 
-          service.to_yaml(**options)[4..-1]
+          { database.name => 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 db_feature_for_devcontainer(database = options[:database])
-          case database
-          when "sqlite3"        then sqlite3_feature
-          when "mysql"          then mysql_feature
-          when "postgresql"     then postgres_feature
-          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" => ["default"],
-              "volumes" => ["mariadb-data:/var/lib/mysql"],
-              "environment" => {
-                "MARIADB_ALLOW_EMPTY_ROOT_PASSWORD" => "true",
-              },
-            }
-          }
-        end
-
-        def db_service_names
-          ["mysql", "mariadb", "postgres"]
-        end
-
-        def mysql_feature
-          { DB_FEATURES["mysql"] => {} }
-        end
-
-        def postgres_feature
-          { DB_FEATURES["postgresql"] => {} }
-        end
-
-        def sqlite3_feature
-          { DB_FEATURES["sqlite3"] => {} }
-        end
-
-        def db_features
-          @db_features ||= DB_FEATURES.values
         end
 
         def local_rails_mount

railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml.tt

@@ -15,10 +15,10 @@ default: &default
   pool: <%%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
   username: root
   password:
-<% if mysql_socket -%>
+<% if database.socket -%>
-  socket: <%= mysql_socket %>
+  socket: <%= database.socket %>
 <% else -%>
-  host: <%= mysql_database_host %>
+  host: <%%= ENV.fetch("DB_HOST") { "<%= database.host %>" } %>
 <% end -%>
 
 development:

railties/lib/rails/generators/rails/app/templates/config/databases/trilogy.yml.tt

@@ -15,10 +15,10 @@ default: &default
   pool: <%%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
   username: root
   password:
-<% if mysql_socket -%>
+<% if database.socket -%>
-  socket: <%= mysql_socket %>
+  socket: <%= database.socket %>
 <% else -%>
-  host: <%= mysql_database_host %>
+  host: <%%= ENV.fetch("DB_HOST") { "<%= database.host %>" } %>
 <% end -%>
 
 development:

railties/lib/rails/generators/rails/app/templates/github/ci.yml.tt

@@ -100,7 +100,7 @@ jobs:
     <%- end -%>
     steps:
       - name: Install packages
-        run: sudo apt-get update && sudo apt-get install --no-install-recommends -y google-chrome-stable <%= (dockerfile_base_packages + [build_package_for_database]).join(" ") %>
+        run: sudo apt-get update && sudo apt-get install --no-install-recommends -y google-chrome-stable <%= (dockerfile_base_packages + [database.base_package]).join(" ") %>
 
       - name: Checkout code
         uses: actions/checkout@v4

railties/lib/rails/generators/rails/db/system/change/change_generator.rb

@@ -9,8 +9,6 @@ module Rails
     module Db
       module System
         class ChangeGenerator < Base # :nodoc:
-          include Database
-          include Devcontainer
           include AppName
 
           class_option :to, required: true,
@@ -24,8 +22,8 @@ module Rails
           def initialize(*)
             super
 
-            unless DATABASES.include?(options[:to])
+            unless Database::DATABASES.include?(options[:to])
-              raise Error, "Invalid value for --to option. Supported preconfigurations are: #{DATABASES.join(", ")}."
+              raise Error, "Invalid value for --to option. Supported preconfigurations are: #{Database::DATABASES.join(", ")}."
             end
 
             opt = options.dup
@@ -38,7 +36,7 @@ module Rails
           end
 
           def edit_gemfile
-            name, version = gem_for_database
+            name, version = database.gem
             gsub_file("Gemfile", all_database_gems_regex, name)
             gsub_file("Gemfile", gem_entry_regex_for(name), gem_entry_for(name, *version))
           end
@@ -47,8 +45,8 @@ module Rails
             dockerfile_path = File.expand_path("Dockerfile", destination_root)
             return unless File.exist?(dockerfile_path)
 
-            base_name = docker_for_database_base
+            base_name = database.docker_base
-            build_name = docker_for_database_build
+            build_name = database.docker_build
             if base_name
               gsub_file("Dockerfile", all_docker_bases_regex, base_name)
             end
@@ -67,15 +65,15 @@ module Rails
 
           private
             def all_database_gems
-              DATABASES.map { |database| gem_for_database(database) }
+              Database.all.map { |database| database.gem }
             end
 
             def all_docker_bases
-              DATABASES.filter_map { |database| docker_for_database_base(database) }
+              Database.all.filter_map { |database| database.docker_base }
             end
 
             def all_docker_builds
-              DATABASES.filter_map { |database| docker_for_database_build(database) }
+              Database.all.filter_map { |database| database.docker_build }
             end
 
             def all_database_gems_regex
@@ -113,19 +111,17 @@ module Rails
 
               compose_config = YAML.load_file(compose_yaml_path)
 
-              db_service_names.each do |db_service_name|
+              Database.all.each do |database|
-                compose_config["services"].delete(db_service_name)
+                compose_config["services"].delete(database.name)
-                compose_config["volumes"]&.delete("#{db_service_name}-data")
+                compose_config["volumes"]&.delete(database.volume)
-                compose_config["services"]["rails-app"]["depends_on"]&.delete(db_service_name)
+                compose_config["services"]["rails-app"]["depends_on"]&.delete(database.name)
               end
 
-              db_service = db_service_for_devcontainer
+              if database.service
-
+                compose_config["services"][database.name] = database.service
-              if db_service
+                compose_config["volumes"] = { database.volume => nil }.merge(compose_config["volumes"] || {})
-                compose_config["services"].merge!(db_service)
-                compose_config["volumes"] = { db_volume_name_for_devcontainer => nil }.merge(compose_config["volumes"] || {})
                 compose_config["services"]["rails-app"]["depends_on"] = [
-                  db_name_for_devcontainer,
+                  database.name,
                   compose_config["services"]["rails-app"]["depends_on"]
                 ].flatten.compact
               end
@@ -138,16 +134,16 @@ module Rails
 
             def update_devcontainer_db_host
               container_env = devcontainer_json["containerEnv"]
-              db_name = db_name_for_devcontainer
+              db_name = database.name
 
               if container_env["DB_HOST"]
-                if db_name
+                if database.service
                   container_env["DB_HOST"] = db_name
                 else
                   container_env.delete("DB_HOST")
                 end
               else
-                if db_name
+                if database.service
                   container_env["DB_HOST"] = db_name
                 end
               end
@@ -159,10 +155,10 @@ module Rails
 
             def update_devcontainer_db_feature
               features = devcontainer_json["features"]
-              db_feature = db_feature_for_devcontainer
+              db_feature = database.feature
 
-              db_features.each do |feature|
+              Database.all.each do |database|
-                features.delete(feature)
+                features.delete(database.feature_name)
               end
 
               features.merge!(db_feature) if db_feature
@@ -181,6 +177,10 @@ module Rails
             def devcontainer_json_path
               File.expand_path(".devcontainer/devcontainer.json", destination_root)
             end
+
+            def database
+              @database ||= Database.build(options[:database])
+            end
         end
       end
     end

railties/test/generators/app_generator_test.rb

@@ -1240,9 +1240,9 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_equal "redis://redis:6379/1", content["containerEnv"]["REDIS_URL"]
       assert_equal "45678", content["containerEnv"]["CAPYBARA_SERVER_PORT"]
       assert_equal "selenium", content["containerEnv"]["SELENIUM_HOST"]
-      assert_equal({}, content["features"]["ghcr.io/rails/devcontainer/features/activestorage"])
+      assert_includes content["features"].keys, "ghcr.io/rails/devcontainer/features/activestorage"
-      assert_equal({}, content["features"]["ghcr.io/devcontainers/features/github-cli:1"])
+      assert_includes content["features"].keys, "ghcr.io/devcontainers/features/github-cli:1"
-      assert_equal({}, content["features"]["ghcr.io/rails/devcontainer/features/sqlite3"])
+      assert_includes content["features"].keys, "ghcr.io/rails/devcontainer/features/sqlite3"
       assert_includes(content["forwardPorts"], 3000)
       assert_includes(content["forwardPorts"], 6379)
     end
@@ -1320,8 +1320,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
     assert_devcontainer_json_file do |content|
       assert_equal "postgres", content["containerEnv"]["DB_HOST"]
-      assert_equal({}, content["features"]["ghcr.io/rails/devcontainer/features/postgres-client"])
+      assert_includes content["features"].keys, "ghcr.io/rails/devcontainer/features/postgres-client"
-      assert_includes(content["forwardPorts"], 5432)
+      assert_includes content["forwardPorts"], 5432
     end
     assert_file("config/database.yml") do |content|
       assert_match(/host: <%= ENV\["DB_HOST"\] %>/, content)
@@ -1350,8 +1350,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
     assert_devcontainer_json_file do |content|
       assert_equal "mysql", content["containerEnv"]["DB_HOST"]
-      assert_equal({}, content["features"]["ghcr.io/rails/devcontainer/features/mysql-client"])
+      assert_includes content["features"].keys, "ghcr.io/rails/devcontainer/features/mysql-client"
-      assert_includes(content["forwardPorts"], 3306)
+      assert_includes content["forwardPorts"], 3306
     end
     assert_file("config/database.yml") do |content|
       assert_match(/host: <%= ENV.fetch\("DB_HOST"\) \{ "localhost" } %>/, content)