Pants

What Pants is

Pants is a free build system for codebases of different sizes, focused on Python, Go, Java, Scala, Kotlin, Shell, and Docker. It installs and coordinates development tools, including compilers, code generators, dependency resolvers, test runners, linters, formatters, packagers, and REPLs. It can examine import statements to infer file dependencies, reducing manual dependency declarations. The build engine is written in Rust, and build rules use typed Python 3. Its execution features include concurrency, fine-grained invalidation, hermetic execution, caching, and remote execution. Developers can add custom rules through a plugin API, which follows the same concurrency, caching, and remoting semantics as core rules. Built-in integrations include Docker, Pex, Protodoc, Thrift, Protobuf, Helm, linting and formatting tools, packaging, and coverage. Lockfiles pin transitive dependency versions and expected SHA256 hashes, which Pants checks against downloaded artifacts. It runs on Linux, macOS, and Windows with WSL 2, subject to specific system requirements.