logfn

This crate provides the logfn attribute macro for inserting logging code into your function.

This is heavily inspired by elichai's log-derive crate.

Currently we support 2 types of logging.

• Pre logging
• Post logging

And we have a plan to add Time logging and Count logging type.

Each logfn attribute injects a single logging code. You can put as many logfn as you want.

# use logfn::logfn;
# use std::num::ParseIntError;
#[logfn(Pre, Debug, "{fn} will be executed")]
#[logfn(Post, Debug, "{fn} is executed", if = "Result::is_ok")]
#[logfn(Post, Error, "Error {fn}: {ret:?}", if = "Result::is_err")]
fn atoi(a: &str) -> Result<usize, ParseIntError> {
    usize::from_str_radix(a, 10)
}

The detail is documented below.

Pre logging

The following attribute injects logging code before function is called.

use logfn::logfn;

#[logfn(Pre, Info, "executing {fn}...")]
fn add(a: usize, b: usize) -> usize {
    a + b
}

The resulting code will looks like

fn add(a: usize, b: usize) -> usize {
    log::info!("executing add...");

    {
        a + b
    }
}

Post logging

You also be able to inject logging code after function is called.

use logfn::logfn;

#[logfn(Post, Info, "executed {fn}!")]
fn add(a: usize, b: usize) -> usize {
    a + b
}

The resulting code will looks like

fn add(a: usize, b: usize) -> usize {
    let res = (move || {
        a + b
    })();

    log::info!("executed add!");

    res
}

Conditional logging

You can configure the condition on which logging code is fired. To do that, please add if argument with a path to the function which takes reference to returned value and returns true when you want to fire the logging code.

Note

Conditional logging is only supported in post logging for now.

use logfn::logfn;

#[logfn(Post, Warn, "checked add is failed!!", if = "Option::is_none")]
fn checked_add(a: usize, b: usize) -> Option<usize> {
    a.checked_add(b)
}

Message formatting

We support below format patterns.

• "{fn}" interpolates function name
• "{ret:?}" or "{ret}" interpolates returned value

# use std::num::ParseIntError;
use logfn::logfn;

#[logfn(Post, Error, "Error while {fn}: {ret:?}", if = "Result::is_err")]
fn atoi(s: &str) -> Result<usize, ParseIntError> {
    usize::from_str_radix(s, 10)
}

Async function

Async function is also supported.

use logfn::logfn;

#[logfn(Post, Debug, "{fn} is executed")]
async fn add_fut(a: usize, b: usize) -> usize {
    a + b
}