New test files are only recognized after cargo clean

[GordianDziwis]

I have a test with the files macro:

  #[rstest]
    fn from(
        #[files("tests/rdf-diagram/*.drawio")] path: PathBuf,
    ) -> anyhow::Result<()> {}

When add/remove a test file, cargo test only shows the updated tests after a cargo clean.

Is this by design, a bug, or a user error?

[la10736]

Unfortunately is not possible to automatize it without writing a build.rs script. I would like to avoid the use of this kind of stuff and ask to the user to introduce a build.rs script in his project just for testing.

But, I'll investigate how to write it and document how to add this support to the project: the idea here is to navigate the code find the #[rstest]'s marked functions with #[files] arguments, take the results and hash them in a key. Use these keys to change the source hash of the build process.

[GordianDziwis]

Do you have an example for an build.rs script achieving this?

[la10736]

No, it's just an idea sketch ... I'll try to write it next weeks (I've not too much time to work on it).

I've putted it here just as my notes.

[la10736]

Ok, I've studied it a little bit and I found that there's a simple solution that should work in the 99% of the cases with just a little effort.

Suppose that you have a project where your test files live in my/resource/folder relative to Cargo.toml manifest project file. Should be enough to add the following line to your build.rs file:

    println!("cargo::rerun-if-changed=my/resource/folder")

You can add a line like this for every folder you need to watch.

Follow a concrete example where your tests files live in resource/tests and in integration_tests/examples folders. If you don't have any build.rs script create one in your crate folder with the following content:

pub fn main() {
    println!("cargo::rerun-if-changed=resource/tests")
    println!("cargo::rerun-if-changed=integration_tests/examples")
}

Maybe in the future I'll write a create to une in build.rs scripts that scan the source to search the #[rstest]'s #[files(...)] attributes and emit these lines in standard output. This crate will automatize this process but my guess that is not a big deal parse all source in build.rs and the handwritten way maybe is the best solution almost of the times.