Standardizing 25 Million Lines How Stripe Unified the World Largest Ruby Codebase.

Inside Stripe Massive Ruby Migration: Formatting 25 Million Lines of Code with Rust

In 2024, engineers Fable Tales and Anna Mason from Stripe embarked on a monumental task: standardizing the formatting of what is likely the world's largest Ruby codebase. Spanning over 62,213 files and 25 million lines of code, the repository lacked a unified style, leading to inconsistent "handwriting" across their global engineering team.

The Failure of Traditional Tools

Stripe’s journey toward a unified format was riddled with obstacles. Their previous attempt using prettier-ruby failed due to performance bottlenecks; the tool was too slow for a codebase of this magnitude, and extra-large files often caused it to crash. Meanwhile, RuboCop, while excellent for linting, proved insufficient as a primary formatter due to its complex configuration, which often led to inconsistent setups among different developers.

The Solution: rubyfmt and the Power of Rust

The team pivoted to rubyfmt, a formatter built with a clear performance mandate: it must execute within 100ms. To achieve this extreme speed, the tool was rewritten in Rust and linked directly to Ruby's C API.

The rollout followed a strategic, phased approach:

1. Opt-in Phase: Developers began by adding a declaration to individual files.

2. The "Big Bang" Migration: On a designated Saturday, the team ran rubyfmt across the entire repository. The resulting patch was so massive that GitHub failed to render it, and the file change count was displayed as "infinity."

The Result: Efficiency Through Enforcement

Two years after the migration, Stripe reports that enforcing a universal formatting standard has significantly increased developer productivity. The friction of "nitpicking" code style during peer reviews has been eliminated, allowing engineers to focus entirely on logic and functionality.

Stripe's success reflects the popularity of opinionated formatters (such as GoFmt or Prettier). The concept is to "eliminate choices" for programmers, resulting in a single standard. Zero configuration eliminates team debates, significantly reducing the cognitive load for developers during code review.

This case is another clear example of the "Rewriting Tools in Rust" trend. When enterprise-level software becomes too large for traditional languages ​​(like Ruby or JavaScript) to process the tools themselves, using Rust to handle heavy workloads becomes the standard solution for large tech companies today.

The fact that the patch shows "Infinity" on GitHub is a reminder that most infrastructure systems aren't designed to handle 25 million lines of code changes at once. Managing projects of this scale requires engineering courage and robust contingency planning, as even a small error could paralyze a company's entire CI/CD system.

 

IBM Granite 4.1 The Compact AI Family Outperforming Tech Giants. 

 

Source: Stripe 

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Inside Stripe Massive Ruby Migration: Formatting 25 Million Lines of Code with Rust

In 2024, engineers Fable Tales and Anna Mason from Stripe embarked on a monumental task: standardizing the formatting of what is likely the world's largest Ruby codebase. Spanning over 62,213 files and 25 million lines of code, the repository lacked a unified style, leading to inconsistent "handwriting" across their global engineering team.

The Failure of Traditional Tools

Stripe’s journey toward a unified format was riddled with obstacles. Their previous attempt using prettier-ruby failed due to performance bottlenecks; the tool was too slow for a codebase of this magnitude, and extra-large files often caused it to crash. Meanwhile, RuboCop, while excellent for linting, proved insufficient as a primary formatter due to its complex configuration, which often led to inconsistent setups among different developers.

The Solution: rubyfmt and the Power of Rust

The team pivoted to rubyfmt, a formatter built with a clear performance mandate: it must execute within 100ms. To achieve this extreme speed, the tool was rewritten in Rust and linked directly to Ruby's C API.

The rollout followed a strategic, phased approach:

1. Opt-in Phase: Developers began by adding a declaration to individual files.

2. The "Big Bang" Migration: On a designated Saturday, the team ran rubyfmt across the entire repository. The resulting patch was so massive that GitHub failed to render it, and the file change count was displayed as "infinity."

The Result: Efficiency Through Enforcement

Two years after the migration, Stripe reports that enforcing a universal formatting standard has significantly increased developer productivity. The friction of "nitpicking" code style during peer reviews has been eliminated, allowing engineers to focus entirely on logic and functionality.

Stripe's success reflects the popularity of opinionated formatters (such as GoFmt or Prettier). The concept is to "eliminate choices" for programmers, resulting in a single standard. Zero configuration eliminates team debates, significantly reducing the cognitive load for developers during code review.

This case is another clear example of the "Rewriting Tools in Rust" trend. When enterprise-level software becomes too large for traditional languages ​​(like Ruby or JavaScript) to process the tools themselves, using Rust to handle heavy workloads becomes the standard solution for large tech companies today.

The fact that the patch shows "Infinity" on GitHub is a reminder that most infrastructure systems aren't designed to handle 25 million lines of code changes at once. Managing projects of this scale requires engineering courage and robust contingency planning, as even a small error could paralyze a company's entire CI/CD system.

 

IBM Granite 4.1 The Compact AI Family Outperforming Tech Giants. 

 

Source: Stripe