uninitialized constant Logger::SimpleFormatter (NameError) after upgrading rails to 6.1.0 and ruby 2.7

Question

Tried by including require 'logger', require 'active_support/logger' in application.rb file.

error: /config/application.rb:64:in `class:Application': uninitialized constant Logger::SimpleFormatter (NameError) Did you mean? SimpleDelegator

Answer 1

Logger::SimpleFormatter was deprecated in rails 4.0, and removed in rails 4.1.

You can use ActiveSupport::Logger::SimpleFormatter instead.

As a general rule, you should never attempt such a large upgrade (v4.0.x --> v6.1.0?!) in one big leap; there are probably countless other errors. Try to go one minor version at a time, and fix deprecations along the way.