Running code before cargo does anything

[yatesco]

Is there a step in the build process where I can run some rust before Cargo.toml is parsed?

In my never ending struggles to get sane management of/synchronise 3rd party dependencies in my workspace, I am considering having a single properties file with the versions in and then doing something clever in build.rs to set the versions in the various Cargo.tomls in the workspace.

I could do this outside of build.rs and alias cargo to call my thing, but build.rs seems neater.

[kornel]

Unfortunately not.

You're going to need to wrap it in some other build system (e.g. make), or hack it hard in build.rs.

There's RUSTC_WRAPPER that may let you do some horrible hacks, but that will happen after Cargo.toml is parsed.

[riking]

Also consider writing an xtask, such as cargo xtask fix-deps

[stonerfish]

Cargo can be extended.
https://doc.rust-lang.org/book/ch14-05-extending-cargo.html
You could make a program or "bash script" to do what you want and call it cargo-before.

js@flower:~/learn/rust/comli$ cat ~/bin/cargo-before
#!/bin/bash
echo "It works!"
cargo b
js@flower:~/learn/rust/comli$ cargo before
It works!
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s

And if in a directory with no Cargo.toml you will notice the "It works!" is before the Cargo.toml parse error.

js@flower:~$ cargo before
It works!
error: could not find `Cargo.toml` in `/home/js` or any parent directory

[yatesco]

thanks all