schema loading rake tasks maintain database connection for current env.

[Joshua Cody & Yves Senn]

Closes #16757.

Prior to this patch schema loading rake tasks had the potential to leak a
connection to a different database. This had side-effects when rake tasks
operating on the current connection (like `db:seed`) were chained.

activerecord/CHANGELOG.md

+*   Schema loading rake tasks (like `db:schema:load` and `db:setup`) maintain
+    the database connection to the current environment.
+
+    Fixes #16757.
+
+    *Joshua Cody*, *Yves Senn*
+
 *   MySQL: set the connection collation along with the charset.
 
     Sets the connection collation to the database collation configured in

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -171,6 +171,7 @@ def purge_current(environment = env)
         each_current_configuration(environment) { |configuration|
           purge configuration
         }
+        ActiveRecord::Base.establish_connection(environment.to_sym)
       end
 
       def structure_dump(*arguments)
@@ -217,6 +218,7 @@ def load_schema_current(format = ActiveRecord::Base.schema_format, file = nil, e
         each_current_configuration(environment) { |configuration|
           load_schema_for configuration, format, file
         }
+        ActiveRecord::Base.establish_connection(environment.to_sym)
       end
 
       def check_schema_file(filename)

activerecord/test/cases/tasks/database_tasks_test.rb

@@ -309,6 +309,7 @@ def test_purges_current_environment_database
 
       ActiveRecord::Tasks::DatabaseTasks.expects(:purge).
         with('database' => 'prod-db')
+      ActiveRecord::Base.expects(:establish_connection).with(:production)
 
       ActiveRecord::Tasks::DatabaseTasks.purge_current('production')
     end

railties/test/application/rake/dbs_test.rb

@@ -173,6 +173,32 @@ def db_test_load_structure
                        "your test schema automatically, see the release notes for details.\n", output
         end
       end
+
+      test 'db:setup loads schema and seeds database' do
+        begin
+          @old_env = ENV["RAILS_ENV"]
+          ENV.delete "RAILS_ENV"
+
+          app_file 'db/schema.rb', <<-RUBY
+            ActiveRecord::Schema.define(version: "1") do
+              create_table :users do |t|
+                t.string :name
+              end
+            end
+          RUBY
+
+          app_file 'db/seeds.rb', <<-RUBY
+            puts ActiveRecord::Base.connection_config[:database]
+          RUBY
+
+          Dir.chdir(app_path) do
+            database_path = `bundle exec rake db:setup`
+            assert_equal "development.sqlite3", File.basename(database_path.strip)
+          end
+        ensure
+          ENV["RAILS_ENV"] = @old_env
+        end
+      end
     end
   end
 end