Use *simplelog* instead of *env_logger*

[KyrietS]

env_logger doesn't support redirecting the output to custom pipe. They have Target but it's broken for a year now and they doesn't seem to care much about it.

simplelog is able to redirect the messages to custom pipes. This would allow me to capture logs in integration tests (not sute if it's a good idea yet). I would be also easier to redirect logs to the file.

Example

This example shows combined logger where ERROR and WARN messages are printed to the console with colors while INFO, WARN and ERROR messages are additionaly captured and stored in a channel waiting to be extracted later.

// [dependencies]
// log = "0.4.0"
// simplelog = "0.11.1"

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

use simplelog::*;

use std::{
    io,
    sync::mpsc::{channel, Sender},
};

struct WriteAdapter {
    sender: Sender<u8>,
}

impl io::Write for WriteAdapter {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        for chr in buf {
            self.sender.send(*chr).unwrap();
        }
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

fn setup_logger() -> std::sync::mpsc::Receiver<u8> {
    let (rx, tx) = channel();
    let my_adapter = WriteAdapter { sender: rx };

    CombinedLogger::init(
        vec![
            TermLogger::new(LevelFilter::Warn, Config::default(), TerminalMode::Mixed, ColorChoice::Auto),
            WriteLogger::new(LevelFilter::Info, Config::default(), my_adapter),
        ]
    ).unwrap();

    return tx;
}

fn main() {
    let tx = setup_logger();

    trace!("some trace log");       // won't be printed
    debug!("some debug log");       // won't be printed
    info!("some information log");  // from pipe
    warn!("some warning log");      // console & from pipe
    error!("some error log");       // console & from pipe

    // Collect all messages send to the channel and parse the result as a string
    String::from_utf8(tx.try_iter().collect::<Vec<u8>>())
        .unwrap()
        // Split the result into lines so a prefix can be added to each line
        .split('\n')
        .for_each(|msg| {
            // Print the message with a prefix if it has any content
            if !msg.is_empty() {
                println!("from pipe: {}", msg)
            }
        });
}