rust/tests/ui/await_holding_lock.rs

#![warn(clippy::await_holding_lock)]

// When adding or modifying a test, please do the same for parking_lot::Mutex.
mod std_mutex {
    use std::sync::{Mutex, RwLock};

    pub async fn bad(x: &Mutex<u32>) -> u32 {
        let guard = x.lock().unwrap();
        baz().await
    }

    pub async fn good(x: &Mutex<u32>) -> u32 {
        {
            let guard = x.lock().unwrap();
            let y = *guard + 1;
        }
        baz().await;
        let guard = x.lock().unwrap();
        47
    }

    pub async fn bad_rw(x: &RwLock<u32>) -> u32 {
        let guard = x.read().unwrap();
        baz().await
    }

    pub async fn bad_rw_write(x: &RwLock<u32>) -> u32 {
        let mut guard = x.write().unwrap();
        baz().await
    }

    pub async fn good_rw(x: &RwLock<u32>) -> u32 {
        {
            let guard = x.read().unwrap();
            let y = *guard + 1;
        }
        {
            let mut guard = x.write().unwrap();
            *guard += 1;
        }
        baz().await;
        let guard = x.read().unwrap();
        47
    }

    pub async fn baz() -> u32 {
        42
    }

    pub async fn also_bad(x: &Mutex<u32>) -> u32 {
        let first = baz().await;

        let guard = x.lock().unwrap();

        let second = baz().await;

        let third = baz().await;

        first + second + third
    }

    pub async fn not_good(x: &Mutex<u32>) -> u32 {
        let first = baz().await;

        let second = {
            let guard = x.lock().unwrap();
            baz().await
        };

        let third = baz().await;

        first + second + third
    }

    #[allow(clippy::manual_async_fn)]
    pub fn block_bad(x: &Mutex<u32>) -> impl std::future::Future<Output = u32> + '_ {
        async move {
            let guard = x.lock().unwrap();
            baz().await
        }
    }
}

// When adding or modifying a test, please do the same for std::Mutex.
mod parking_lot_mutex {
    use parking_lot::{Mutex, RwLock};

    pub async fn bad(x: &Mutex<u32>) -> u32 {
        let guard = x.lock();
        baz().await
    }

    pub async fn good(x: &Mutex<u32>) -> u32 {
        {
            let guard = x.lock();
            let y = *guard + 1;
        }
        baz().await;
        let guard = x.lock();
        47
    }

    pub async fn bad_rw(x: &RwLock<u32>) -> u32 {
        let guard = x.read();
        baz().await
    }

    pub async fn bad_rw_write(x: &RwLock<u32>) -> u32 {
        let mut guard = x.write();
        baz().await
    }

    pub async fn good_rw(x: &RwLock<u32>) -> u32 {
        {
            let guard = x.read();
            let y = *guard + 1;
        }
        {
            let mut guard = x.write();
            *guard += 1;
        }
        baz().await;
        let guard = x.read();
        47
    }

    pub async fn baz() -> u32 {
        42
    }

    pub async fn also_bad(x: &Mutex<u32>) -> u32 {
        let first = baz().await;

        let guard = x.lock();

        let second = baz().await;

        let third = baz().await;

        first + second + third
    }

    pub async fn not_good(x: &Mutex<u32>) -> u32 {
        let first = baz().await;

        let second = {
            let guard = x.lock();
            baz().await
        };

        let third = baz().await;

        first + second + third
    }

    #[allow(clippy::manual_async_fn)]
    pub fn block_bad(x: &Mutex<u32>) -> impl std::future::Future<Output = u32> + '_ {
        async move {
            let guard = x.lock();
            baz().await
        }
    }
}

fn main() {
    let m = std::sync::Mutex::new(100);
    std_mutex::good(&m);
    std_mutex::bad(&m);
    std_mutex::also_bad(&m);
    std_mutex::not_good(&m);
    std_mutex::block_bad(&m);

    let m = parking_lot::Mutex::new(100);
    parking_lot_mutex::good(&m);
    parking_lot_mutex::bad(&m);
    parking_lot_mutex::also_bad(&m);
    parking_lot_mutex::not_good(&m);
}