A Rust macro to part of the log facade that auto generates loggings for functions output.
Add this to your Cargo.toml:
```toml [dependencies] log-derive = "0.2" log = "0.4"
```
and for Rust Edition 2015 add this to your crate root:
```rust
extern crate logderive;
extern crate log;
In Rust Edition 2018 you can simply do:
rust
use logderive::logfn;
```
After that all you need is to add the macro above a function that returns an output that implements the Debug trait.
```rust #[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( () ) }
```
```rust
fn testlog(a: u8) -> String { (a*2).tostring() }
```
The output of the fibonacci example:
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 2
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 3
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 2
14:55:41 [INFO] fibonacci() -> 5
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 2
14:55:41 [INFO] fibonacci() -> 1
14:55:41 [INFO] fibonacci() -> 3
14:55:41 [INFO] fibonacci() -> 8
If you expand the output of the macro the resulting code will look something like this:
rust
fn fibonacci(n: u32) -> u32 {
let result = (move || match n {
0 => 1,
1 => 1,
_ => fibonacci(n - 1) + fibonacci(n - 2),
})();
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