log-derive

A Rust macro to part of the log facade that auto generates loggings for functions output.

• Documentation

Usage

Add this to your Cargo.toml:

[dependencies]
log-derive = "0.2"
log = "0.4"

and for Rust Edition 2015 add this to your crate root:

#[macro_use]
extern crate log_derive;
extern crate log;

In Rust Edition 2018 you can simply do:

use log_derive::logfn;

After that all you need is to add the macro above a function that returns an output that implements the Debug trait.

Examples

 #[logfn(Err = "Error", fmt = "Failed Sending Packet: {:?}")]
 fn send_hi(addr: SocketAddr) -> Result<(), io::Error> {
     let mut stream = TcpStream::connect(addr)?;
     stream.write(b"Hi!")?;
     Ok( () )
 }

#[logfn(Trace)]
fn test_log(a: u8) -> String {
  (a*2).to_string()
}

Output

The output of the fibonacci example:

20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(2)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(3)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(2)
20:34:21 [INFO] fibonacci(5)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(2)
20:34:21 [INFO] fibonacci(1)
20:34:21 [INFO] fibonacci(3)
20:34:21 [INFO] fibonacci(8)

If you expand the output of the macro the resulting code will look something like this:

fn fibonacci(n: u32) -> u32 {
    let mut closure = || match n {
        0 => 1,
        1 => 1,
        _ => fibonacci(n - 1) + fibonacci(n - 2),
    };
    let result = closure();
    log::log!(log::Level::Info, "fibonacci({})", result);
    result
}

Of course the log! macro will be expanded too and it will be a bit more messy.

If the function returns a Result it will match through it to split between the Ok LogLevel and the Err LogLevel