Rake tasks for managing database while development and testing of engines

Some of the engines needs database. As engine needs to be run inside
Rails application, migrations and other database operations are run
from dummy application. To make that process simple I changed db
tasks to look for migrations in both engine's and application's
db/migrate directory. You can run all of the database tasks from
test/dummy or directly from engine with prefix app, like:

  rake app:db:migrate
  rake app:db:migrate:redo

activerecord/lib/active_record/railties/databases.rake

@@ -1,4 +1,4 @@
-namespace :db do
+db_namespace = namespace :db do
   task :load_config => :rails_env do
     require 'active_record'
     ActiveRecord::Base.configurations = Rails.application.config.database_configuration
@@ -141,18 +141,18 @@ namespace :db do
   task :migrate => [:environment, :load_config] do
     ActiveRecord::Migration.verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] == "true" : true
     ActiveRecord::Migrator.migrate(ActiveRecord::Migrator.migrations_paths, ENV["VERSION"] ? ENV["VERSION"].to_i : nil)
-    Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+    db_namespace["schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
   end
 
   namespace :migrate do
     # desc  'Rollbacks the database one migration and re migrate up (options: STEP=x, VERSION=x).'
     task :redo => [:environment, :load_config] do
       if ENV["VERSION"]
-        Rake::Task["db:migrate:down"].invoke
-        Rake::Task["db:migrate:up"].invoke
+        db_namespace["migrate:down"].invoke
+        db_namespace["migrate:up"].invoke
       else
-        Rake::Task["db:rollback"].invoke
-        Rake::Task["db:migrate"].invoke
+        db_namespace["rollback"].invoke
+        db_namespace["migrate"].invoke
       end
     end
 
@@ -164,7 +164,7 @@ namespace :db do
       version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
       raise "VERSION is required" unless version
       ActiveRecord::Migrator.run(:up, ActiveRecord::Migrator.migrations_paths, version)
-      Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+      db_namespace["schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
     end
 
     # desc 'Runs the "down" for a given migration VERSION.'
@@ -172,7 +172,7 @@ namespace :db do
       version = ENV["VERSION"] ? ENV["VERSION"].to_i : nil
       raise "VERSION is required" unless version
       ActiveRecord::Migrator.run(:down, ActiveRecord::Migrator.migrations_paths, version)
-      Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+      db_namespace["schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
     end
 
     desc "Display status of migrations"
@@ -210,14 +210,14 @@ namespace :db do
   task :rollback => [:environment, :load_config] do
     step = ENV['STEP'] ? ENV['STEP'].to_i : 1
     ActiveRecord::Migrator.rollback(ActiveRecord::Migrator.migrations_paths, step)
-    Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+    db_namespace["schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
   end
 
   # desc 'Pushes the schema to the next version (specify steps w/ STEP=n).'
   task :forward => [:environment, :load_config] do
     step = ENV['STEP'] ? ENV['STEP'].to_i : 1
     ActiveRecord::Migrator.forward(ActiveRecord::Migrator.migrations_paths, step)
-    Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+    db_namespace["schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
   end
 
   # desc 'Drops and recreates the database from db/schema.rb for the current environment and loads the seeds.'
@@ -321,12 +321,12 @@ namespace :db do
 
   namespace :schema do
     desc "Create a db/schema.rb file that can be portably used against any DB supported by AR"
-    task :dump => :environment do
+    task :dump => :load_config do
       require 'active_record/schema_dumper'
       File.open(ENV['SCHEMA'] || "#{Rails.root}/db/schema.rb", "w") do |file|
         ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
       end
-      Rake::Task["db:schema:dump"].reenable
+      db_namespace["schema:dump"].reenable
     end
 
     desc "Load a schema.rb file into the database"
@@ -383,7 +383,7 @@ namespace :db do
     task :load => 'db:test:purge' do
       ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations['test'])
       ActiveRecord::Schema.verbose = false
-      Rake::Task["db:schema:load"].invoke
+      db_namespace["schema:load"].invoke
     end
 
     # desc "Recreate the test database from the current environment's database schema"
@@ -457,7 +457,7 @@ namespace :db do
     # desc 'Check for pending migrations and load the test schema'
     task :prepare => 'db:abort_if_pending_migrations' do
       if defined?(ActiveRecord) && !ActiveRecord::Base.configurations.blank?
-        Rake::Task[{ :sql  => "db:test:clone_structure", :ruby => "db:test:load" }[ActiveRecord::Base.schema_format]].invoke
+        db_namespace[{ :sql  => "test:clone_structure", :ruby => "test:load" }[ActiveRecord::Base.schema_format]].invoke
       end
     end
   end

railties/lib/rails/generators/rails/plugin_new/plugin_new_generator.rb

@@ -70,6 +70,16 @@ task :default => :test
       if mountable?
         template "rails/routes.rb", "#{dummy_path}/config/routes.rb", :force => true
       end
+
+      if full? && !options[:skip_active_record]
+        append_file "#{dummy_path}/Rakefile", <<-EOF
+
+task :"db:load_config" do
+  ActiveRecord::Migrator.migrations_paths = Rails.application.config.paths["db/migrate"].to_a +
+                                            <%= camelized %>::Engine.config.paths["db/migrate"].to_a
+end
+        EOF
+      end
     end
 
     def test_dummy_clean

railties/lib/rails/generators/rails/plugin_new/templates/Rakefile

@@ -14,3 +14,15 @@ Rake::RDocTask.new(:rdoc) do |rdoc|
   rdoc.rdoc_files.include('README.rdoc')
   rdoc.rdoc_files.include('lib/**/*.rb')
 end
+
+<% if full? && !options[:skip_active_record] -%>
+namespace :app do
+  load File.expand_path("../<%= dummy_path -%>/Rakefile", __FILE__)
+
+  task :"db:load_config" do
+    ActiveRecord::Migrator.migrations_paths = Rails.application.config.paths["db/migrate"].to_a +
+                                              <%= camelized %>::Engine.config.paths["db/migrate"].to_a
+  end
+end
+<% end -%>
+

railties/lib/rails/generators/rails/plugin_new/templates/test/test_helper.rb

@@ -6,10 +6,5 @@ require "rails/test_help"
 
 Rails.backtrace_cleaner.remove_silencers!
 
-<% if  full? && !options[:skip_active_record] -%>
-# Run any available migration from application
-ActiveRecord::Migrator.migrate File.expand_path("../dummy/db/migrate/", __FILE__)
-<% end  -%>
-
 # Load support files
 Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }

railties/test/generators/plugin_new_generator_test.rb

@@ -114,7 +114,7 @@ class PluginNewGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_ensure_that_tests_works_in_full_mode
-    run_generator [destination_root, "--full"]
+    run_generator [destination_root, "--full", "--skip_active_record"]
     FileUtils.cd destination_root
     `bundle install`
     assert_match /2 tests, 2 assertions, 0 failures, 0 errors/, `bundle exec rake test`