Vakyartha documentation

1//! Keeps the build stamp honest, and composes the version string.
2//!
3//! Two jobs, both about the same fact — which commit this binary is.
4//!
5//! 1. `VAK_GIT_SHA` is read with `option_env!`, which is baked in at COMPILE
6//! time. Cargo does not know an arbitrary environment variable is a build
7//! input, so without `rerun-if-env-changed` it happily reuses a cached
8//! object compiled against an older value, and `install.json` then records
9//! the commit of whenever that object was last built. A manifest naming
10//! the wrong commit is worse than one saying nothing: it is what an
11//! operator reads to answer "what is deployed here", and a confidently
12//! stale answer sends them debugging code that was never running.
13//!
14//! 2. `VAK_VERSION` is the string `--version` prints. Composing it here
15//! rather than in the CLI because `concat!` takes only literals, so
16//! "release, plus a sha if there is one" cannot be expressed inline.
17//!
18//! `scripts/build.sh` and `scripts/release.sh` set the sha; a plain
19//! `cargo build` leaves it unset and both the manifest and `--version`
20//! honestly report just the release.
21
22fn main() {
23 println!("cargo:rerun-if-env-changed=VAK_GIT_SHA");
24
25 let version = std::env::var("CARGO_PKG_VERSION").unwrap_or_default();
26 let stamped = match std::env::var("VAK_GIT_SHA") {
27 Ok(sha) if !sha.trim().is_empty() && sha != "unknown" => {
28 format!("{version} ({})", sha.trim())
29 }
30 _ => version,
31 };
32 println!("cargo:rustc-env=VAK_VERSION={stamped}");
33}
34