Record does not contain file location and module for log messages from isahc crate, but works with env_logger

[e00E]

When using isahc https://crates.io/crates/isahc log records are missing location information when logging them through slog. The information exists when logging through env_logger https://crates.io/crates/env_logger .

Cargo.toml:

[package]
name = "temp"
version = "0.1.0"
edition = "2018"

[dependencies]
env_logger = "0.7.1"
isahc = "0.9.3"
log = "0.4.8"
slog = "2.5.2"
slog-scope = "4.3.0"
slog-stdlog = "4.0.0"

main.rs:

pub struct CustomFormatter;
impl slog::Drain for CustomFormatter {
    type Ok = ();
    type Err = ();
    fn log(
        &self,
        record: &slog::Record,
        _values: &slog::OwnedKVList,
    ) -> std::result::Result<Self::Ok, Self::Err> {
        println!(
            "{} {} {} {}: {}",
            record.level(),
            record.module(),
            record.file(),
            record.line(),
            record.msg()
        );
        Ok(())
    }
}

fn env_logger_format(
    formatter: &mut env_logger::fmt::Formatter,
    record: &log::Record,
) -> std::io::Result<()> {
    use std::io::Write as _;
    writeln!(
        formatter,
        "{} {} {} {}: {}",
        record.level(),
        record.module_path().unwrap(),
        record.file().unwrap(),
        record.line().unwrap(),
        record.args()
    )
    .unwrap();
    Ok(())
}

fn setup_env_logger() {
    env_logger::Builder::new()
        .filter_level(log::LevelFilter::Trace)
        .format(env_logger_format)
        .init();
}

fn setup_slog_logger() -> slog_scope::GlobalLoggerGuard {
    use slog::Drain as _;
    let logger = slog::Logger::root(CustomFormatter {}.fuse(), slog::o!());
    let guard = slog_scope::set_global_logger(logger);
    slog_stdlog::init().unwrap();
    guard
}

fn main() {
    // setup_env_logger();
    let _guard = setup_slog_logger();
    log::info!("start");
    isahc::HttpClient::new().unwrap();
    log::info!("end");
}

cargo run:

INFO temp src/main.rs 32: start
INFO <unknown> <unknown> 505: new
INFO <unknown> <unknown> 505: -> new
INFO <unknown> <unknown> 372: build
...

Change which logger is enabled:

    setup_env_logger();
    // let _guard = setup_slog_logger();

cargo run:

INFO temp src/main.rs 58: start
INFO isahc::client /home/u/.cargo/registry/src/github.com-1ecc6299db9ec823/isahc-0.9.3/src/client.rs 505: new
INFO isahc::client /home/u/.cargo/registry/src/github.com-1ecc6299db9ec823/isahc-0.9.3/src/client.rs 505: -> new
INFO isahc::client /home/u/.cargo/registry/src/github.com-1ecc6299db9ec823/isahc-0.9.3/src/client.rs 372: build
...

I am not sure which crate is at fault but slog is most likely as it works with env_logger.

[dpc]

https://github.com/slog-rs/stdlog/blob/8ba187532ca5f60adbe217f5295d5e04d4aa41a1/lib.rs#L69

https://docs.rs/log/0.4.8/src/log/lib.rs.html#800

[dpc]

slog/src/lib.rs

Line 2425 in 4868ddb

pub struct RecordLocation {

Historically log was using &'static str for module names. So slog used it to. Then log crate changed it to &'str, but changing it in slog would create a big split in the ecosystem.

It is possible to no one got to it yet, and log did (or is planing to?) add structured logging support etc. so I'm not sure if it is worth the trouble.

Maybe we could just do string interning (+ clone + box + leak) to turn non-&'static strings into &'static ones? I mean - how many module strings can a program have ...

I think that would work well. PRs welcome!