Context Manager

Library offering an easy access Python like decorators in rust

Via this library we can easily alter the content of a defined function, by injecting code to be executed before/after the original function, without altering the original function itself.

For example, let's assume that we are interested on logging the duration of the execution of a function.

fn function_to_be_decorated() -> usize {
    # let do_something_expensive = || 1234;
    do_something_expensive()
}

In order to achieve so we would need to manually modify it similarly to

fn function_to_be_decorated() -> usize {
    # let do_something_expensive = || 1234;
    let start = std::time::Instant::now();
    let return_value = do_something_expensive();
    println!("Duration of function_to_be_decorated is: {}ms", start.elapsed().as_millis());
    return_value
}

As far as this could be very simple, it is tedious and requires to actually modify the original function. While having a simple decorator that would do it for us would be much more convenient. Leading to something like

# use context_manager::SyncWrapContext;
# struct PrintDuration;
# impl<T> SyncWrapContext<T> for PrintDuration { fn new() -> Self { Self } }
#[context_manager::wrap(PrintDuration)]
fn function_to_be_wrapped() -> usize {
    # let do_something_expensive = || 1234;
    do_something_expensive()
}

How does the library work internally?

The library exposes 2 main traits that allows users to customize the wrapping logic

• SyncWrapContext for synchronous context management (which is supported for decorating sync and async functions)
• AsyncWrapContext for asynchronous context management (which is supported ONLY for async functions)

and 2 main attribute macros (wrap and async_wrap) that allow an easy plug-and-play of the logic into the code

License