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Getting started with bolt

bolt is Volt’s build tool: Cargo’s workflow, without a registry. It builds packages and their dependencies (local paths and git repositories, pinned in a lock file), with features, profiles, tests, benchmarks and build files written in Volt.

Terminal window
bolt new app          # a program; bolt new --lib util for a library
cd app
bolt run              # build and run
bolt build --release  # optimized, into target/release/
bolt test             # build and run every program in tests/

A package

Section titled “A package”

A package is a directory with a bolt.toml:

[package]
name = "app"
version = "0.1.0"

and its sources, found by convention:

app/
├── bolt.toml
├── src/          the program: every .volt file here is one executable, `app`
├── lib/          the library: other packages call it as app::name
├── examples/     one program per .volt file or subdirectory (bolt run --example NAME)
├── tests/        one program per file or subdirectory; each must exit 0 (bolt test)
├── benches/      one program per file or subdirectory, built with the bench profile (bolt bench)
└── target/       build output: target/debug/, target/release/, ...

A package can have a program, a library, or both. Its library is in namespace NAME, the package’s name, for everyone including its own program.

What a build does

Section titled “What a build does”

bolt reads the manifest (and the workspace’s, if it’s in one), resolves dependencies and bolt.lock, turns on features, then calls voltc: every library (std, each dependency, the package’s own lib/) is compiled once per profile into target/<profile>/deps/libNAME.a, in parallel when they don’t depend on each other, and rebuilt only when its sources, its settings or voltc change. Executables are cached the same way.

bolt runs $VOLTC when set, otherwise a voltc next to itself or on PATH, then a voltc-bootstrap next to itself.

Other languages

Section titled “Other languages”

Both directions are a line in bolt.toml. [lib] bindings = ["python", "node", ...] writes the library’s bindings for those languages, and builds the ones that need compiling (a Node addon, Lua and Ruby modules). [foreign] names a Rust crate, a Zig file or a Go module the package uses: bolt builds it, writes its C header and links it in. See the bolt.toml reference and Rust, Zig and Go.

Next

Section titled “Next”