blacklisted_name should not be triggered in tests

[tamaroning]

Summary

blacklisted_name should toralate use of such name as foo.
As far as I see the source code, it tries to allow foo in tests, but it doesn't.

Similar to #8758

Lint Name

blacklisted_name

Reproducer

I tried this code:

#![warn(clippy::blacklisted_name)]
fn main() {}

#[cfg(test)]
mod abc {
    fn _abc() {
        let foo = ();
        dbg!(foo);
    }
}

#[test]
fn bcd() {
    let foo = ();
    dbg!(foo);
}

fn _test() {
    let foo = ();
    dbg!(foo);
}

I saw this happen:

warning: use of a blacklisted/placeholder name `foo`
  --> src\main.rs:19:9
   |
19 |     let foo = ();
   |         ^^^
   |
note: the lint level is defined here
  --> src\main.rs:1:9
   |
1  | #![warn(clippy::blacklisted_name)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name

warning: use of a blacklisted/placeholder name `foo`
 --> src\main.rs:7:13
  |
7 |         let foo = ();
  |             ^^^
  |
note: the lint level is defined here
 --> src\main.rs:1:9
  |
1 | #![warn(clippy::blacklisted_name)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name

warning: use of a blacklisted/placeholder name `foo`
  --> src\main.rs:14:9
   |
14 |     let foo = ();
   |         ^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name

warning: use of a blacklisted/placeholder name `foo`
  --> src\main.rs:19:9
   |
19 |     let foo = ();
   |         ^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name

I expected to see this happen:
No warning

Version

rustc 1.61.0-nightly (458262b13 2022-03-09)
binary: rustc
commit-hash: 458262b1315e0de7be940fe95e111bb045e4a2a4
commit-date: 2022-03-09
host: x86_64-pc-windows-msvc
release: 1.61.0-nightly
LLVM version: 14.0.0

Additional Labels

@rustbot label +E-easy

[kyoto7250]

@tamaroning

Hello.

I tried your code, but the following two cases cannot be reproduced. (rust playrground)

(If the verification method is incorrect, please let me know.)

#![warn(clippy::blacklisted_name)]
fn main() {}

#[cfg(test)]
mod abc {
    fn _abc() {
        let foo = ();
        dbg!(foo);
    }
}

#[test]
fn bcd() {
    let foo = ();
    dbg!(foo);
}

last case, I think we should not lint.
They should be ignored in test cases only.

#[cfg(test)] and #[test] are codes that are ignored except when the test is run, but I don't think the name fn test has such a restriction.

[tamaroning]

@kyoto7250

I tried your code, but the following two cases cannot be reproduced.

Playground seems not to pass --tests flag to the compiler so I ran clippy in local enviroment.

..., but I don't think the name fn test has such a restriction.

Yes. I reconsider this and agree with you. But the lint has been fixed in PR #7379 in order to trigger on fn test.

[kyoto7250]

@tamaroning

Playground seems not to pass --tests flag to the compiler so I ran clippy in local enviroment.

I can reproduce now, thanks!

It doesn't seem urgent, so I hope someone interested will do it.

[yerke]

@rustbot claim

[yerke]

I think the lint is working as intended right now.

For the following input:

#![warn(clippy::blacklisted_name)]
fn main() {}

#[cfg(test)]
mod abc {
    fn _abc() {
        let foo = ();
        dbg!(foo);
    }
}

#[test]
fn bcd() {
    let foo = ();
    dbg!(foo);
}

fn _test() {
    let foo = ();
    dbg!(foo);
}

mod tests {
    fn _mf() {
        let foo = ();
        dbg!(foo);
    }
}

I get only 1 warning:

warning: use of a blacklisted/placeholder name `foo`
  --> src/main.rs:19:9
   |
19 |     let foo = ();
   |         ^^^
   |
note: the lint level is defined here
  --> src/main.rs:1:9
   |
1  | #![warn(clippy::blacklisted_name)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#blacklisted_name

warning: `clippy-example-1` (bin "clippy-example-1") generated 1 warning

Which is expected, since the function _test is a standalone function and is not part of any tests.
mod tests is ignored, since it contains tests in it.

The is_test_module_or_function function this lint relies on seems to work according to its description:

rust-clippy/clippy_utils/src/lib.rs

Lines 2220 to 2228 in 580f642

	/// Checks whether item either has `test` attribute applied, or
	/// is a module with `test` in its name.
	///
	/// Note: Add `// compile-flags: --test` to UI tests with a `#[test]` function
	pub fn is_test_module_or_function(tcx: TyCtxt<'_>, item: &Item<'_>) -> bool {
	is_in_test_function(tcx, item.hir_id())
	|| matches!(item.kind, ItemKind::Mod(..))
	&& item.ident.name.as_str().split('_').any(|a| a == "test" || a == "tests")
	}

Does my reasoning make sense or not?