alinuxperson / try-drop

Batteries included error handling mechanisms for drops which can fail

try-drop

Batteries included error handling mechanisms for drops which can fail

Quick Usage

For Clients

...where clients mean structures that may fail dropping,

Implement TryDrop for your type and adapt it like so:

use try_drop::TryDrop;

pub struct Foo { /* fields */ }

impl TryDrop for Foo {
    type Error = Error;
    
    unsafe fn try_drop(&mut self) -> Result<(), Self::Error> {
        // do stuff
        Ok(())
    }
}

let foo = Foo.adapt();

...or, if you want to avoid the adapt boilerplate:

use try_drop::{TryDrop, adapters::DropAdapter};

pub struct FooInner { /* fields */ }

impl TryDrop for FooInner {
    type Error = Error;
    
    unsafe fn try_drop(&mut self) -> Result<(), Self::Error> {
        // do stuff
        Ok(())
    }
}

pub struct Foo(pub DropAdapter<FooInner>);

impl Foo {
    pub fn from_inner(inner: FooInner) -> Self {
        Foo(DropAdapter(inner))
    }
}

We must adapt it because implementing TryDrop doesn't also implement Drop with your type. This is due to the orphan rules and the fact that Drop can only be implemented for structs, enums, and unions, but not generics. With this, if dropping Foo fails, it will automatically print the error to standard error.

For Servers

...where servers mean how to handle the drop errors (also means drop strategies),

Implement TryDropStrategy for your structure.

use try_drop::TryDropStrategy;

pub struct Strategy { /* fields */ }

impl TryDropStrategy for Strategy {
    fn handle_error(&self, error: try_drop::Error) {
        // handle the error here
    }
}

...then install either for this thread,

try_drop::install_thread_local_handlers(Strategy, /* other strategy, use the `PanicDropStrategy` if you don't know */)

...install it globally (meaning if no thread local strategies are set, use this),

try_drop::install_global_handlers(Strategy, /* other strategy */)

...or, if possible, install it for a structure.

struct Sample<D = ShimPrimaryHandler, DD = ShimFallbackHandler>
where
    D: FallibleTryDropStrategy,
    DD: TryDropStrategy,
{
    primary: D,
    fallback: DD,
    /* other fields */
}

impl<D, DD> Sample<D, DD>
where
    D: FallibleTryDropStrategy,
    DD: TryDropStrategy,
{
    pub fn new_with(/* other arguments */ primary: D, fallback: DD) -> Self {
        Self {
            // filled arguments
            primary,
            fallback,
        }
    }
}

let sample = Sample::new_with(Strategy, /* other strategy */)

License

This project is licensed under the MIT License.