schema rake tasks are specific about the configuration to act on.

The rake tasks and the `DatabaseTakss` adapter classes used to
assume a configuration at some places. This forced the rake
tasks to establish a specific connection before calling into
`load_schema`.

After #15394 this started to cause issues because it could
`purge` the wrong database before loading the schema.

Author: senny

activerecord/CHANGELOG.md

@@ -1,3 +1,16 @@
+*   Deprecate `DatabaseTasks.load_schema` to act on the current connection.
+    Use `.load_schema_current` instead. In the future `load_schema` will
+    require the `configuration` to act on as an argument.
+
+    *Yves Senn*
+
+*   Fixed automatic maintaining test schema to properly handle sql structure
+    schema format.
+
+    Fixes #15394.
+
+    *Wojciech Wnętrzak*
+
 *   Fix type casting to Decimal from Float with large precision.
 
     *Tomohiro Hashidate*
@@ -297,14 +310,7 @@
 
     Fixes #8328.
 
-    Sean Griffin
-
-*   Fixed automatic maintaining test schema to properly handle sql structure
-    schema format.
-
-    Fixes #15394.
-
-    *Wojciech Wnętrzak*
+    *Sean Griffin*
 
 *   Pluck now works when selecting columns from different tables with the same
     name.

activerecord/lib/active_record/migration.rb

@@ -399,7 +399,7 @@ def check_pending!(connection = Base.connection)
 
       def load_schema_if_pending!
         if ActiveRecord::Migrator.needs_migration?
-          ActiveRecord::Tasks::DatabaseTasks.load_schema
+          ActiveRecord::Tasks::DatabaseTasks.load_schema_current
           check_pending!
         end
       end

activerecord/lib/active_record/railties/databases.rake

@@ -240,7 +240,7 @@ db_namespace = namespace :db do
 
     desc 'Load a schema.rb file into the database'
     task :load => [:environment, :load_config] do
-      ActiveRecord::Tasks::DatabaseTasks.load_schema(:ruby, ENV['SCHEMA'])
+      ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:ruby, ENV['SCHEMA'])
     end
 
     task :load_if_ruby => ['db:create', :environment] do
@@ -286,7 +286,7 @@ db_namespace = namespace :db do
 
     desc "Recreate the databases from the structure.sql file"
     task :load => [:environment, :load_config] do
-      ActiveRecord::Tasks::DatabaseTasks.load_schema(:sql, ENV['DB_STRUCTURE'])
+      ActiveRecord::Tasks::DatabaseTasks.load_schema_current(:sql, ENV['DB_STRUCTURE'])
     end
 
     task :load_if_sql => ['db:create', :environment] do
@@ -317,9 +317,8 @@ db_namespace = namespace :db do
     task :load_schema => %w(db:test:deprecated db:test:purge) do
       begin
         should_reconnect = ActiveRecord::Base.connection_pool.active_connection?
-        ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations['test'])
         ActiveRecord::Schema.verbose = false
-        db_namespace["schema:load"].invoke
+        ActiveRecord::Tasks::DatabaseTasks.load_schema_for ActiveRecord::Base.configurations['test'], :ruby, ENV['SCHEMA']
       ensure
         if should_reconnect
           ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[ActiveRecord::Tasks::DatabaseTasks.env])
@@ -329,12 +328,7 @@ db_namespace = namespace :db do
 
     # desc "Recreate the test database from an existent structure.sql file"
     task :load_structure => %w(db:test:deprecated db:test:purge) do
-      begin
-        ActiveRecord::Tasks::DatabaseTasks.current_config(:config => ActiveRecord::Base.configurations['test'])
-        db_namespace["structure:load"].invoke
-      ensure
-        ActiveRecord::Tasks::DatabaseTasks.current_config(:config => nil)
-      end
+      ActiveRecord::Tasks::DatabaseTasks.load_schema_for ActiveRecord::Base.configurations['test'], :sql, ENV['SCHEMA']
     end
 
     # desc "Recreate the test database from a fresh schema"

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -184,22 +184,39 @@ def structure_load(*arguments)
       end
 
       def load_schema(format = ActiveRecord::Base.schema_format, file = nil)
+        ActiveSupport::Deprecation.warn(<<-MESSAGE.strip_heredoc)
+          This method will act on a specific connection in the future.
+          To act on the current connection, use `load_schema_current` instead.
+        MESSAGE
+        load_schema_current(format, file)
+      end
+
+      # This method is the successor of +load_schema+. We should rename it
+      # after +load_schema+ went through a deprecation cycle. (Rails > 4.2)
+      def load_schema_for(configuration, format = ActiveRecord::Base.schema_format, file = nil) # :nodoc:
         case format
         when :ruby
           file ||= File.join(db_dir, "schema.rb")
           check_schema_file(file)
-          purge(current_config)
+          purge(configuration)
+          ActiveRecord::Base.establish_connection(configuration)
           load(file)
         when :sql
           file ||= File.join(db_dir, "structure.sql")
           check_schema_file(file)
-          purge(current_config)
-          structure_load(current_config, file)
+          purge(configuration)
+          structure_load(configuration, file)
         else
           raise ArgumentError, "unknown format #{format.inspect}"
         end
       end
 
+      def load_schema_current(format = ActiveRecord::Base.schema_format, file = nil, environment = env)
+        each_current_configuration(environment) { |configuration|
+          load_schema_for configuration, format, file
+        }
+      end
+
       def check_schema_file(filename)
         unless File.exist?(filename)
           message = %{#{filename} doesn't exist yet. Run `rake db:migrate` to create it, then try again.}