Merge pull request #34832 from gmcgibbon/db_system_change_command

Add rails db:system:change command

12 files changed, 378 insertions, 89 deletions

diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 3691bb3fb1..9c7e958b7c 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,7 +1,20 @@
+*   Add `rails db:system:change` command for changing databases.
+
+    ```
+    bin/rails db:system:change --to=postgresql
+       force  config/database.yml
+        gsub  Gemfile
+    ```
+
+    The change command copies a template `config/database.yml` with the target database adapter into your app, and replaces your database gem with the target database gem.
+
+    *Gannon McGibbon*
+
 *   Add `rails test:channels`.
 
     *bogdanvlviv*
 
+
 *   Use original `bundler` environment variables during the process of generating a new rails project.
 
     *Marco Costa*
diff --git a/railties/lib/rails/commands/db/system/change/change_command.rb b/railties/lib/rails/commands/db/system/change/change_command.rb
new file mode 100644
index 0000000000..760c229c07
--- /dev/null
+++ b/railties/lib/rails/commands/db/system/change/change_command.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "rails/generators"
+require "rails/generators/rails/db/system/change/change_generator"
+
+module Rails
+  module Command
+    module Db
+      module System
+        class ChangeCommand < Base # :nodoc:
+          class_option :to, desc: "The database system to switch to."
+
+          def perform
+            Rails::Generators::Db::System::ChangeGenerator.start
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index caf8a33c3c..b835b3f3fd 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -23,6 +23,8 @@ module Rails
     autoload :ActiveModel,     "rails/generators/active_model"
     autoload :Base,            "rails/generators/base"
     autoload :Migration,       "rails/generators/migration"
+    autoload :Database,        "rails/generators/database"
+    autoload :AppName,         "rails/generators/app_name"
     autoload :NamedBase,       "rails/generators/named_base"
     autoload :ResourceHelpers, "rails/generators/resource_helpers"
     autoload :TestCase,        "rails/generators/test_case"
@@ -218,6 +220,7 @@ module Rails
         rails.delete("encryption_key_file")
         rails.delete("master_key")
         rails.delete("credentials")
+        rails.delete("db:system:change")
 
         hidden_namespaces.each { |n| groups.delete(n.to_s) }
 
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index 8df2b32dd2..8278abcaeb 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -11,9 +11,8 @@ require "active_support/core_ext/array/extract_options"
 module Rails
   module Generators
     class AppBase < Base # :nodoc:
-      DATABASES = %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver )
-      JDBC_DATABASES = %w( jdbcmysql jdbcsqlite3 jdbcpostgresql jdbc )
-      DATABASES.concat(JDBC_DATABASES)
+      include Database
+      include AppName
 
       attr_accessor :rails_template
       add_shebang_option!
@@ -106,7 +105,6 @@ module Rails
         @gem_filter    = lambda { |gem| true }
         @extra_entries = []
         super
-        convert_database_option_for_jruby
       end
 
     private
@@ -306,34 +304,6 @@ module Rails
         end
       end
 
-      def gem_for_database
-        # %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver jdbcmysql jdbcsqlite3 jdbcpostgresql )
-        case options[:database]
-        when "mysql"          then ["mysql2", [">= 0.4.4"]]
-        when "postgresql"     then ["pg", [">= 0.18", "< 2.0"]]
-        when "oracle"         then ["activerecord-oracle_enhanced-adapter", nil]
-        when "frontbase"      then ["ruby-frontbase", nil]
-        when "sqlserver"      then ["activerecord-sqlserver-adapter", nil]
-        when "jdbcmysql"      then ["activerecord-jdbcmysql-adapter", nil]
-        when "jdbcsqlite3"    then ["activerecord-jdbcsqlite3-adapter", nil]
-        when "jdbcpostgresql" then ["activerecord-jdbcpostgresql-adapter", nil]
-        when "jdbc"           then ["activerecord-jdbc-adapter", nil]
-        else [options[:database], nil]
-        end
-      end
-
-      def convert_database_option_for_jruby
-        if defined?(JRUBY_VERSION)
-          opt = options.dup
-          case opt[:database]
-          when "postgresql" then opt[:database] = "jdbcpostgresql"
-          when "mysql"      then opt[:database] = "jdbcmysql"
-          when "sqlite3"    then opt[:database] = "jdbcsqlite3"
-          end
-          self.options = opt.freeze
-        end
-      end
-
       def assets_gemfile_entry
         return [] if options[:skip_sprockets]
 
diff --git a/railties/lib/rails/generators/app_name.rb b/railties/lib/rails/generators/app_name.rb
new file mode 100644
index 0000000000..c4f71694d8
--- /dev/null
+++ b/railties/lib/rails/generators/app_name.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module Rails
+  module Generators
+    module AppName # :nodoc:
+      RESERVED_NAMES = %w(application destroy plugin runner test)
+
+      private
+        def app_name
+          @app_name ||= original_app_name.tr("-", "_")
+        end
+
+        def original_app_name
+          @original_app_name ||= (defined_app_const_base? ? defined_app_name : File.basename(destination_root)).tr('\\', "").tr(". ", "_")
+        end
+
+        def defined_app_name
+          defined_app_const_base.underscore
+        end
+
+        def defined_app_const_base
+          Rails.respond_to?(:application) && defined?(Rails::Application) &&
+            Rails.application.is_a?(Rails::Application) && Rails.application.class.name.chomp("::Application")
+        end
+
+        alias :defined_app_const_base? :defined_app_const_base
+
+        def app_const_base
+          @app_const_base ||= defined_app_const_base || app_name.gsub(/\W/, "_").squeeze("_").camelize
+        end
+        alias :camelized :app_const_base
+
+        def app_const
+          @app_const ||= "#{app_const_base}::Application"
+        end
+
+        def valid_const?
+          if /^\d/.match?(app_const)
+            raise Error, "Invalid application name #{original_app_name}. Please give a name which does not start with numbers."
+          elsif RESERVED_NAMES.include?(original_app_name)
+            raise Error, "Invalid application name #{original_app_name}. Please give a " \
+                         "name which does not match one of the reserved rails " \
+                         "words: #{RESERVED_NAMES.join(", ")}"
+          elsif Object.const_defined?(app_const_base)
+            raise Error, "Invalid application name #{original_app_name}, constant #{app_const_base} is already in use. Please choose another application name."
+          end
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/database.rb b/railties/lib/rails/generators/database.rb
new file mode 100644
index 0000000000..be3e61bde8
--- /dev/null
+++ b/railties/lib/rails/generators/database.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module Rails
+  module Generators
+    module Database # :nodoc:
+      JDBC_DATABASES = %w( jdbcmysql jdbcsqlite3 jdbcpostgresql jdbc )
+      DATABASES = %w( mysql postgresql sqlite3 oracle frontbase ibm_db sqlserver ) + JDBC_DATABASES
+
+      def initialize(*)
+        super
+        convert_database_option_for_jruby
+      end
+
+      def gem_for_database(database = options[:database])
+        case database
+        when "mysql"          then ["mysql2", [">= 0.4.4"]]
+        when "postgresql"     then ["pg", [">= 0.18", "< 2.0"]]
+        when "oracle"         then ["activerecord-oracle_enhanced-adapter", nil]
+        when "frontbase"      then ["ruby-frontbase", nil]
+        when "sqlserver"      then ["activerecord-sqlserver-adapter", nil]
+        when "jdbcmysql"      then ["activerecord-jdbcmysql-adapter", nil]
+        when "jdbcsqlite3"    then ["activerecord-jdbcsqlite3-adapter", nil]
+        when "jdbcpostgresql" then ["activerecord-jdbcpostgresql-adapter", nil]
+        when "jdbc"           then ["activerecord-jdbc-adapter", nil]
+        else [database, nil]
+        end
+      end
+
+      def convert_database_option_for_jruby
+        if defined?(JRUBY_VERSION)
+          opt = options.dup
+          case opt[:database]
+          when "postgresql" then opt[:database] = "jdbcpostgresql"
+          when "mysql"      then opt[:database] = "jdbcmysql"
+          when "sqlite3"    then opt[:database] = "jdbcsqlite3"
+          end
+          self.options = opt.freeze
+        end
+      end
+
+      private
+        def mysql_socket
+          @mysql_socket ||= [
+            "/tmp/mysql.sock",                        # default
+            "/var/run/mysqld/mysqld.sock",            # debian/gentoo
+            "/var/tmp/mysql.sock",                    # freebsd
+            "/var/lib/mysql/mysql.sock",              # fedora
+            "/opt/local/lib/mysql/mysql.sock",        # fedora
+            "/opt/local/var/run/mysqld/mysqld.sock",  # mac + darwinports + mysql
+            "/opt/local/var/run/mysql4/mysqld.sock",  # mac + darwinports + mysql4
+            "/opt/local/var/run/mysql5/mysqld.sock",  # mac + darwinports + mysql5
+            "/opt/lampp/var/mysql/mysql.sock"         # xampp for linux
+          ].find { |f| File.exist?(f) } unless Gem.win_platform?
+        end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index e777590be8..5f6e817bf6 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -242,7 +242,6 @@ module Rails
     # We need to store the RAILS_DEV_PATH in a constant, otherwise the path
     # can change in Ruby 1.8.7 when we FileUtils.cd.
     RAILS_DEV_PATH = File.expand_path("../../../../../..", __dir__)
-    RESERVED_NAMES = %w[application destroy plugin runner test]
 
     class AppGenerator < AppBase # :nodoc:
       WEBPACKS = %w( react vue angular elm stimulus )
@@ -269,7 +268,7 @@ module Rails
         super
 
         if !options[:skip_active_record] && !DATABASES.include?(options[:database])
-          raise Error, "Invalid value for --database option. Supported for preconfiguration are: #{DATABASES.join(", ")}."
+          raise Error, "Invalid value for --database option. Supported preconfigurations are: #{DATABASES.join(", ")}."
         end
 
         # Force sprockets and yarn to be skipped when generating API only apps.
@@ -491,60 +490,6 @@ module Rails
         create_file(*args, &block)
       end
 
-      def app_name
-        @app_name ||= original_app_name.tr("-", "_")
-      end
-
-      def original_app_name
-        @original_app_name ||= (defined_app_const_base? ? defined_app_name : File.basename(destination_root)).tr('\\', "").tr(". ", "_")
-      end
-
-      def defined_app_name
-        defined_app_const_base.underscore
-      end
-
-      def defined_app_const_base
-        Rails.respond_to?(:application) && defined?(Rails::Application) &&
-          Rails.application.is_a?(Rails::Application) && Rails.application.class.name.sub(/::Application$/, "")
-      end
-
-      alias :defined_app_const_base? :defined_app_const_base
-
-      def app_const_base
-        @app_const_base ||= defined_app_const_base || app_name.gsub(/\W/, "_").squeeze("_").camelize
-      end
-      alias :camelized :app_const_base
-
-      def app_const
-        @app_const ||= "#{app_const_base}::Application"
-      end
-
-      def valid_const?
-        if /^\d/.match?(app_const)
-          raise Error, "Invalid application name #{original_app_name}. Please give a name which does not start with numbers."
-        elsif RESERVED_NAMES.include?(original_app_name)
-          raise Error, "Invalid application name #{original_app_name}. Please give a " \
-                       "name which does not match one of the reserved rails " \
-                       "words: #{RESERVED_NAMES.join(", ")}"
-        elsif Object.const_defined?(app_const_base)
-          raise Error, "Invalid application name #{original_app_name}, constant #{app_const_base} is already in use. Please choose another application name."
-        end
-      end
-
-      def mysql_socket
-        @mysql_socket ||= [
-          "/tmp/mysql.sock",                        # default
-          "/var/run/mysqld/mysqld.sock",            # debian/gentoo
-          "/var/tmp/mysql.sock",                    # freebsd
-          "/var/lib/mysql/mysql.sock",              # fedora
-          "/opt/local/lib/mysql/mysql.sock",        # fedora
-          "/opt/local/var/run/mysqld/mysqld.sock",  # mac + darwinports + mysql
-          "/opt/local/var/run/mysql4/mysqld.sock",  # mac + darwinports + mysql4
-          "/opt/local/var/run/mysql5/mysqld.sock",  # mac + darwinports + mysql5
-          "/opt/lampp/var/mysql/mysql.sock"         # xampp for linux
-        ].find { |f| File.exist?(f) } unless Gem.win_platform?
-      end
-
       def get_builder_class
         defined?(::AppBuilder) ? ::AppBuilder : Rails::AppBuilder
       end
diff --git a/railties/lib/rails/generators/rails/db/system/change/change_generator.rb b/railties/lib/rails/generators/rails/db/system/change/change_generator.rb
new file mode 100644
index 0000000000..63849eb18d
--- /dev/null
+++ b/railties/lib/rails/generators/rails/db/system/change/change_generator.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "rails/generators/base"
+
+module Rails
+  module Generators
+    module Db
+      module System
+        class ChangeGenerator < Base # :nodoc:
+          include Database
+          include AppName
+
+          class_option :to, required: true,
+            desc: "The database system to switch to."
+
+          def self.default_generator_root
+            path = File.expand_path(File.join(base_name, "app"), base_root)
+            path if File.exist?(path)
+          end
+
+          def initialize(*)
+            super
+
+            unless DATABASES.include?(options[:to])
+              raise Error, "Invalid value for --to option. Supported preconfigurations are: #{DATABASES.join(", ")}."
+            end
+
+            opt = options.dup
+            opt[:database] ||= opt[:to]
+            self.options = opt.freeze
+          end
+
+          def edit_database_config
+            template("config/databases/#{options[:database]}.yml", "config/database.yml")
+          end
+
+          def edit_gemfile
+            database_gem_name, _ = gem_for_database
+            gsub_file("Gemfile", all_database_gems_regex, database_gem_name)
+          end
+
+          private
+            def all_database_gems
+              DATABASES.map { |database| gem_for_database(database) }
+            end
+
+            def all_database_gems_regex
+              all_database_gem_names = all_database_gems.map(&:first)
+              /(\b#{all_database_gem_names.join('\b|\b')}\b)/
+            end
+        end
+      end
+    end
+  end
+end
diff --git a/railties/test/commands/db_system_change_test.rb b/railties/test/commands/db_system_change_test.rb
new file mode 100644
index 0000000000..2ff45a7878
--- /dev/null
+++ b/railties/test/commands/db_system_change_test.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "rails/command"
+require "rails/commands/db/system/change/change_command"
+
+class Rails::Command::Db::System::ChangeCommandTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation
+
+  setup { build_app }
+
+  teardown { teardown_app }
+
+  test "change to existing database" do
+    change_database(to: "sqlite3")
+
+    output = change_database(to: "sqlite3")
+
+    assert_match "identical  config/database.yml", output
+    assert_match "gsub  Gemfile", output
+  end
+
+  test "change to invalid database" do
+    output = change_database(to: "invalid-db")
+
+    assert_match <<~MSG.squish, output
+      Invalid value for --to option.
+      Supported preconfigurations are:
+      mysql, postgresql, sqlite3, oracle, frontbase,
+      ibm_db, sqlserver, jdbcmysql, jdbcsqlite3,
+      jdbcpostgresql, jdbc.
+    MSG
+  end
+
+  test "change to postgresql" do
+    output = change_database(to: "postgresql")
+
+    assert_match "force  config/database.yml", output
+    assert_match "gsub  Gemfile", output
+  end
+
+  test "change to mysql" do
+    output = change_database(to: "mysql")
+
+    assert_match "force  config/database.yml", output
+    assert_match "gsub  Gemfile", output
+  end
+
+  test "change to sqlite3" do
+    change_database(to: "postgresql")
+    output = change_database(to: "sqlite3")
+
+    assert_match "force  config/database.yml", output
+    assert_match "gsub  Gemfile", output
+  end
+
+  private
+    def change_database(to:, **options)
+      args = ["--to", to]
+      rails "db:system:change", args, **options
+    end
+end
diff --git a/railties/test/generators/db_system_change_generator_test.rb b/railties/test/generators/db_system_change_generator_test.rb
new file mode 100644
index 0000000000..d476bfd2dc
--- /dev/null
+++ b/railties/test/generators/db_system_change_generator_test.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+require "generators/generators_test_helper"
+require "rails/generators/rails/db/system/change/change_generator"
+
+module Rails
+  module Generators
+    module Db
+      module System
+        class ChangeGeneratorTest < Rails::Generators::TestCase
+          include GeneratorsTestHelper
+
+          setup do
+            copy_gemfile(
+              GemfileEntry.new("sqlite3", nil, "Use sqlite3 as the database for Active Record")
+            )
+          end
+
+          test "change to invalid database" do
+            output = capture(:stderr) do
+              run_generator ["--to", "invalid-db"]
+            end
+
+            assert_match <<~MSG.squish, output
+              Invalid value for --to option.
+              Supported preconfigurations are:
+              mysql, postgresql, sqlite3, oracle, frontbase,
+              ibm_db, sqlserver, jdbcmysql, jdbcsqlite3,
+              jdbcpostgresql, jdbc.
+            MSG
+          end
+
+          test "change to postgresql" do
+            run_generator ["--to", "postgresql"]
+
+            assert_file("config/database.yml") do |content|
+              assert_match "adapter: postgresql", content
+              assert_match "database: test_app", content
+            end
+
+            assert_file("Gemfile") do |content|
+              assert_match "# Use pg as the database for Active Record", content
+              assert_match "gem 'pg'", content
+            end
+          end
+
+          test "change to mysql" do
+            run_generator ["--to", "mysql"]
+
+            assert_file("config/database.yml") do |content|
+              assert_match "adapter: mysql2", content
+              assert_match "database: test_app", content
+            end
+
+            assert_file("Gemfile") do |content|
+              assert_match "# Use mysql2 as the database for Active Record", content
+              assert_match "gem 'mysql2'", content
+            end
+          end
+
+          test "change to sqlite3" do
+            run_generator ["--to", "sqlite3"]
+
+            assert_file("config/database.yml") do |content|
+              assert_match "adapter: sqlite3", content
+              assert_match "db/development.sqlite3", content
+            end
+
+            assert_file("Gemfile") do |content|
+              assert_match "# Use sqlite3 as the database for Active Record", content
+              assert_match "gem 'sqlite3'", content
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/railties/test/generators/generators_test_helper.rb b/railties/test/generators/generators_test_helper.rb
index 25d5dba1d8..975a204af4 100644
--- a/railties/test/generators/generators_test_helper.rb
+++ b/railties/test/generators/generators_test_helper.rb
@@ -30,6 +30,12 @@ module GeneratorsTestHelper
   include ActiveSupport::Testing::Stream
   include ActiveSupport::Testing::MethodCallAssertions
 
+  GemfileEntry = Struct.new(:name, :version, :comment, :options, :commented_out) do
+    def initialize(name, version, comment, options = {}, commented_out = false)
+      super
+    end
+  end
+
   def self.included(base)
     base.class_eval do
       destination File.join(Rails.root, "tmp")
@@ -63,4 +69,34 @@ module GeneratorsTestHelper
     FileUtils.mkdir_p(destination)
     FileUtils.cp routes, File.join(destination, "routes.rb")
   end
+
+  def copy_gemfile(*gemfile_entries)
+    locals = gemfile_locals.merge(gemfile_entries: gemfile_entries)
+    gemfile = File.expand_path("../../lib/rails/generators/rails/app/templates/Gemfile.tt", __dir__)
+    gemfile = evaluate_template(gemfile, locals)
+    destination = File.join(destination_root)
+    File.write File.join(destination, "Gemfile"), gemfile
+  end
+
+  def evaluate_template(file, locals = {})
+    erb = ERB.new(File.read(file), nil, "-", "@output_buffer")
+    context = Class.new do
+      locals.each do |local, value|
+        class_attribute local, default: value
+      end
+    end
+    erb.result(context.new.instance_eval("binding"))
+  end
+
+  private
+    def gemfile_locals
+      {
+        skip_active_storage: true,
+        depend_on_bootsnap: false,
+        depend_on_listen: false,
+        spring_install: false,
+        depends_on_system_test: false,
+        options: ActiveSupport::OrderedOptions.new,
+      }
+    end
 end
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 7d4a26ff9d..01b6cb0a43 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -476,7 +476,7 @@ Module.new do
     `yarn build`
   end
 
-  `#{Gem.ruby} #{RAILS_FRAMEWORK_ROOT}/railties/exe/rails new #{app_template_path} --skip-gemfile --skip-listen --no-rc`
+  `#{Gem.ruby} #{RAILS_FRAMEWORK_ROOT}/railties/exe/rails new #{app_template_path} --skip-bundle --skip-listen --no-rc`
   File.open("#{app_template_path}/config/boot.rb", "w") do |f|
     f.puts "require 'rails/all'"
   end