Usage

Begin by adding build-info as a [dependency] and build-info-build as a [build-dependency] to your Cargo.toml. By separating those two crates, pure compile-time dependencies, such as git2 are not compiled into your final program. For this to work properly, ensure to opt in to resolver "2". Please also make sure that both dependencies use the same version!

If it does not already exist, add a build.rs to your project's root, where you call build_info_build::build_script(). This will collect build information at compile time.

Then, either use the build_info! macro to add a function that returns version information at runtime:

build_info::build_info!(fn version);

or use build_info::format! to generate a string at compile time:

// sample output: "{sample v0.0.13 built with rustc 1.45.0-nightly (4bd32c980 2020-05-29) at 2020-05-30 11:22:46Z}"
build_info::format!("{{{} v{} built with {} at {}}}", $.crate_info.name, $.crate_info.version, $.compiler, $.timestamp)

The sample project shows both variants.

Features

The build_info package supports several feature flags:

• The runtime feature enables build_info::build_info!. It is enabled by default, but if you intend to only use build_info::format!, it is safe to disable this flag.
• The nested feature adds support for proc-macro-nested, which lets the build_info::format! macro be nested inside other proc-macros. This may require you to set #![recursion_limit = "..."] in your crate. The feature is disabled by default.
• The chrono feature enables the default features of the chrono package, which is used by build_info::build_info!. It is disabled by default.
• The pyo3 feature enables the use of build_info types in a pyo3-Python enabled application, including extension modules. For example, a function build_info::build_info!(fn version); can be added to a module by using module.add_function(wrap_pyfunction!(version, m)?)?;. Note that this feature is not needed to just add the __version__ tag to your module, which can be facilitated via my_module.add("__version__", build_info::format!("{}", $.crate_info.version))?;.
• The serde feature adds Serialize/Deserialize support to the types used by build_info::build_info!. It is disabled by default.

Caveats

As of the time of writing, Rust does not support function-like proc-macros used as expressions. The format! macro can often still be used as an expression, thanks to the proc-macro-hack crate. However, its result will not behave like a string literal in all cases; for example, it cannot be used as an argument to concat!.

The build script will ask cargo to rerun it whenever the project or the currently checked out commit changes. It will not necessarily be rerun if only the dependencies change (build_info_build::build_script will try to find the lockfile and depend on it, but it is not really aware of any of the more intricate features, such as, cargo workspaces). Please open an issue if your specific use case requires a more strict rerun policy for build.rs and include a short description what additional files should trigger a rebuild when changed.