Use shadow-rs to embed sha1 and other build-time information in the code

When a user reports an error it is crucial to know which version of the application they use. The shadow-rs crates makes it very easy to embed the version number found in Cargo.toml along with a lot of additional build-time information. For example the exact sha1 from the most recent commit in git, and a plethora of other pieces of data.

For this example I basically followed the README of the crate

Dependencies in Cargo.toml

examples/use-shadow/Cargo.toml

[package]
name = "use-shadow"
version = "0.1.0"
edition = "2021"
build = "build.rs"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
shadow-rs = "0.26.1"


[build-dependencies]
shadow-rs = "0.26.1"

I've included

build = "build.rs"

in the Cargo.toml, despite the fact that it seems it is not necessary.

Build code

examples/use-shadow/build.rs

fn main() -> shadow_rs::SdResult<()> {
    shadow_rs::new()
}

Code

In the README of the Crate there are a lot more variables with a lot more details, but I was mainly interested in these:

examples/use-shadow/src/main.rs

use shadow_rs::shadow;

shadow!(build);

fn main() {
    println!("branch:  {}", build::BRANCH);
    println!("version: {}", build::PKG_VERSION);
    println!("sha1:    {}", build::SHORT_COMMIT);


    let rust_version_parts = build::RUST_VERSION.split_whitespace().collect::<Vec<&str>>();
    let rust_version = if rust_version_parts.len() == 4 { rust_version_parts[1] } else { "NA" };
    println!("rust:    {}", rust_version);
}

Build and run

This is how you build a release from your crate:

cargo buld --release

Then I moved the generated binary to some other location:

mv target/release/use-shadow ~/

Then I ran the program

cd ~
./use-shadow

$ ./use-shadow
branch:  main
version: 0.1.0
sha1:    9b773fe2
rust:    1.76.0

Real world usage

I a real world application I'd probably include the version number in the output of the --version flag, maybe along with the sha1.

Then I'd add another flag, for example -V that would display a lot more details.

Why do I need the sha1 ?

If I already have the version number, why do I need the sha1?

In at least one project every time I push to GitHub, it runs some tests and then generates a released binary. It won't make sense to change the version number in Cargo.toml for every commit so we will have multiple releases with the same version number. In this case it is quite important to know which sha1 it was built from.