dropcatch 0.1.0

Drop detection library for Rust.
Documentation 
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use std::{fmt::Debug, sync::Arc};

#[derive(Clone)]
pub struct DropCatcher<F>
where F: FnOnce() + Send + 'static
{
    #[cfg(feature = "random-id")]
    id: [u8; 16],
    _inner: Arc<DropCatcherInner<F>>
}

impl<F> DropCatcher<F>
where F: FnOnce() + Send + 'static
{
    pub fn new(f: F) -> Self {
        Self {
            #[cfg(feature = "random-id")]
            id: rand::random(),

            _inner: Arc::new(DropCatcherInner { f: Some(f) }),
        }
    }
}

impl<F> Debug for DropCatcher<F>
where 
    F: FnOnce() + Send + 'static
{
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str("DropCatcher")
    }
}

#[cfg(feature = "random-id")]
mod random_id_traits {
    use std::hash::Hash;

    use super::DropCatcher;

    impl<F1, F2> PartialEq<DropCatcher<F2>> for DropCatcher<F1>
    where
        F1: FnOnce() + Send + 'static,
        F2: FnOnce() + Send + 'static,
    {
        fn eq(&self, other: &DropCatcher<F2>) -> bool {
            self.id == other.id
        }
    }

    impl<F> Hash for DropCatcher<F>
    where
        F: FnOnce() + Send + 'static,
    {
        fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
            state.write(&self.id);
        }
    }
}

struct DropCatcherInner<F>
where F: FnOnce() + Send + 'static
{
    f: Option<F>,
}

impl<F> Drop for DropCatcherInner<F>
where F: FnOnce() + Send + 'static
{
    fn drop(&mut self) {
        self.f.take().map(|f| {
            f();
        });
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::{Arc, Mutex};

    #[test]
    fn drop_check() {
        let flag = Arc::new(Mutex::new(false));
        let flag_clone = flag.clone();
        {
            #[allow(unused_variables)]
            let dropped = DropCatcher::new(move || {
                *flag_clone.lock().unwrap() = true;
            });
        }

        assert!(*flag.lock().unwrap());
    }

    #[allow(dead_code)]
    #[cfg_attr(feature = "random-id", test)]
    fn id_check() {
        let flag = Arc::new(Mutex::new(false));
        let flag_clone = flag.clone();
        {
            let dropped = DropCatcher::new(move || {
                *flag_clone.lock().unwrap() = true;
            });

            let dropped_clone = dropped.clone();

            assert_eq!(dropped, dropped_clone);

            drop(dropped);
            assert!(!*flag.lock().unwrap());
        }

        assert!(*flag.lock().unwrap());
    }
}