bring back `db:test:prepare`.

This reverts deprecations added in #13528.
The task is brought back for two reasons:
  1. Give plugins a way to hook into the test database initialization process
  2. Give the user a way to force a test database synchronization

While `test:prepare` is still a dependency of every test task, `db:test:prepare`
no longer hooks into it. This means that `test:prepare` runs before the schema
is synchronized. Plugins, which insert data can now hook into `db:test:prepare`.

The automatic schema maintenance can't detect when a migration is rolled-back,
modified and reapplied. In this case the user has to fall back to `db:test:prepare`
to force the synchronization to happen.

1 files changed, 8 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 4e00eb3d99..92f2951f2d 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -395,7 +395,14 @@ module ActiveRecord
 
       def load_schema_if_pending!
         if ActiveRecord::Migrator.needs_migration? || !ActiveRecord::Migrator.any_migrations?
-          ActiveRecord::Tasks::DatabaseTasks.load_schema_current_if_exists
+          # Roundrip to Rake to allow plugins to hook into database initialization.
+          FileUtils.cd Rails.root do
+            current_config = Base.connection_config
+            Base.clear_all_connections!
+            system("bin/rake db:test:prepare")
+            # Establish a new connection, the old database may be gone (db:test:prepare uses purge)
+            Base.establish_connection(current_config)
+          end
           check_pending!
         end
       end