Retrieve the version of a dependency in build.rs script - rust

Question

I would like to expose in my REPL (built on top of Boa) the version of the js engine:
I'm trying to use a build.rs file for that:
use std::env;
fn main() {
println!("cargo:rustc-env=BOA_VERSION={}", "0.16.0");
}
And somewhere in my main.rs:
context.register_global_property("BOA_VERSION", env!("BOA_VERSION"), Attribute::all());
Obviously I have hardcoded the version of the crate but wondering if there is a programmatically way to get the version.

Answer 1

If all you need is to get access to the version information in your code, you can skip making a build.rs file for it. Instead, we can use the serde and toml crates to parse your Cargo.toml file directly. Below is a sample of how that might look.
Cargo.toml:
[package]
name = "dependency-information"
version = "0.1.0"
edition = "2021"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
serde = { version = "1.0.152", features = ["derive"] }
toml = "0.7.0"
main.rs:
use std::collections::HashMap;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize)]
#[serde(untagged)]
enum DependencyValue {
String(String),
Object {
version: String,
features: Vec<String>,
},
}
#[derive(Debug, Serialize, Deserialize)]
struct CargoToml {
dependencies: HashMap<String, DependencyValue>,
}
fn main() {
let cargo_toml_raw = include_str!("../Cargo.toml");
let cargo_toml: CargoToml = toml::from_str(cargo_toml_raw).unwrap();
println!("{cargo_toml:#?}");
}
And if we run it, we get this output:
CargoToml {
dependencies: {
"toml": String(
"0.7.0",
),
"serde": Object {
version: "1.0.152",
features: [
"derive",
],
},
},
}
Note that you probably would want to include the Cargo.toml file dynamically instead of using include_str!. I used include_str! for the sake of the example.