#[cfg(not(test))] doesn't work in dependencies

[nhynes]

I have something that looks like

// crateA/lib.rs

#[cfg(not(test))]
extern "C" {
	fn ext_fn();
}

#[cfg(test)]
fn ext_fn() {
	unimplemented!();
}

pub fn do_ext() {
	unsafe { ext_fn() };
}

// crateB/lib.rs
crateA::do_ext()

but despite using cargo test, I still get a link error saying that ext_fn isn't found. Is #[cfg(not(test))] a valid attribute?

[jonas-schievink]

AFAIK cargo test only applies cfg(test) to the crate you run it in, not to any dependencies.

[nhynes]

That's unfortunate. It seems that a workaround is to use [features] test = [], but it'd be nice if conditional compilation flags were propagated through the entire graph.

[sfackler]

This would be best filed on cargo, not rustc itself, but I don't think we want to rebuild the entire dependency tree for tests necessarily.

[mleduque]

Was there a follow-up issue somewhere else for this bug?

[mimoo]

IIRC, the way we fixed that in diem was to have a [features] testing = [] in every crate Cargo.toml, and import dependencies with this feature in [dev-dependencies] (see https://github.com/diem/diem/blob/0cdde0d258a3706d7d84d05225899df8518f319a/testsuite/smoke-test/Cargo.toml#L52 for an example):

[dev-dependencies]
diem-genesis-tool = {path = "../../config/management/genesis", features = ["testing"] }

but then in every other crate you had to do stuff like

if cfg!(any(test, feature = "testing")) {
  // ...
}

and

#[cfg(any(test, feature = "testing"))]
// ...

instead of just having "test"

it's a pain