Add capability to ignore arguments

[edward-shen]

Hey!

We have a macro that passes in a value to our tests, e.g.

#[company::test]
async fn(init_token: InitToken) { /* ... */ }

Normally, we could just generate a fixture, but the problem is that construction of this init token is unsafe. This results in a lot of libraries/binaries with an unsafe fixture just for this:

fn init_token() -> InitToken {
    unsafe { InitToken::do_dangerous() }
}

#[rstest]
#[company::test]
async fn(init_token: InitToken, my_arg: &str) { /* ... */ }

I was wondering if it was possible to support the ability to ignore certain parameters, something like this:

#[rstest]
#[company::test]
async fn(#[rstest::ignore] init_token: InitToken, my_arg: &str) { /* ... */ }

so that our macro could safely construct this token and pass that value in.

Thanks!

[la10736]

Could be a good idea but I prefer to use just #[ignore] instead. Anyway I've no time to implement it: any PR will be welcomed. I can point you to the right direction.... should be simple.

[edward-shen]

Sure! I can try to take a look. Where would you suggest?

[la10736]

There are two steps:

1. Parsing : where you extract the #[ignore] attributes and store a flag
2. Rendering : where you should filter out the ignored arguments from the ones that are injected with value or fixture call.

ArgumentInfo

rstest/rstest_macros/src/parse/mod.rs

Line 644 in b32e182

pub(crate) struct ArgumentInfo {

is the struct where we can add a ignore flag and we can implement a is_ignore() method in ArgumentsInfo

rstest/rstest_macros/src/parse/mod.rs

Line 673 in b32e182

impl ArgumentsInfo {

For parsing stage you can take a look to rstest_macros::parse::future module to see how to implement and test it.

For rendering should be enough filter out the ignored arguments in

rstest/rstest_macros/src/render/mod.rs

Line 258 in b32e182

let inject = inject::resolve_aruments(args.iter(), &resolver, generic_types);

Maybe the hardest part is to find a way to write an end to end test.... I've no idea.

Please remember to add a changelog line and document the new feature.