Ruby 4.0 moves ten gems from the default standard library to bundled gems. We cover the full list, rationale, app impacts, and Gemfile updates.

RubyFlow's platform is a resource for Ruby developers, offering insights into Ruby programming language, Ruby on Rails framework, and Ruby-related tools. Through articles, tutorials, and community discussions, RubyFlow offers insights into building web applications with Ruby and Rails. Developers can learn about Ruby gems, Rails conventions, and best practices in Ruby development to write clean and maintainable code.

Ruby Flow

Ruby 4.0 moves ten gems from default to bundled status, meaning they no longer load automatically without a Gemfile entry. The affected gems include benchmark, irb, logger, ostruct, rdoc, win32ole, pstore, fiddle, reline, and others. The change can silently break apps if dependencies that previously pulled these gems in are removed. Key migration steps include auditing your codebase for direct usage and adding explicit Gemfile entries. The post also highlights OpenStruct's performance and safety issues, recommending Ruby 3.2's Data.define as a faster, immutable alternative. Stripping unused bundled gems can reduce Docker image size by up to ~37MB.

Preparing for Ruby 4.0: Ten Gems Moving from Default Standard Library to Bundled

What “Core” vs “Default” vs. “Bundled” Actually Means