A Packwerk Retrospective | Rails at Scale

In September, 2020, our team at Shopify released a Ruby gem named Packwerk, a tool to enforce boundaries and modularize Rails applications. Since its release, Packwerk has taken on a life of its own, inspiring blog posts, conference talks, and even an entire gem ecosystem. Its popularity is an indication that Packwerk clearly filled a void in the Rails community.Packwerk is a static analysis tool, similar to tools like Rubocop and Sorbet. Applied to a codebase, it analyzes constant references to help decouple code and organize it into well-defined packages.But Packwerk is more than just a tool. Over the years, Packwerk’s approach to modularity has come to embody distinct and sometimes conflicting perspectives on code organization and its evolution. Packwerk’s feedback can change the entire trajectory of a codebase to a degree that distinguishes it from other tools of its kind.This retrospective is our effort, as the team that developed Packwerk at Shopify, to shine a light on our learnings working with the tool, concerns about its use, and hopes for its future.