Simpler Build Tools with Functional and Object Oriented Programming, Scala Workshop 2025

Haoyi Li explores why build tools are complex and demonstrates how the Mill build tool uses FP and OOP principles to simplify them.

Many Scala developers say SBT is “too complex”, but it’s actually a broader problem: users of Maven, Gradle, Bazel, and other build tools all have the same complaint! This talk will explore why build tooling is fundamentally such a difficult domain to work in, and how common concepts from functional and object-oriented programming have the potential to simplify the build tool experience. We will demonstrate how the Mill build tool makes use of these ideas, proving out the idea that build tooling - inside and outside the Scala community - has the potential to be much faster, safer, and easier than it is today.