Initializing Rust env_logger with the settings that I like

init_logger.rs

// colored = "2"
// chrono = "0"
// env_logger = "0"
// log = "0"

use colored::*;
use std::io::Write;

fn init_logger(default_level: LevelFilter) {
    // extract the value of RUST_LOG if it exists
    let env_val = std::env::var(env_logger::DEFAULT_FILTER_ENV)
        .ok()
        .unwrap_or("".into());

    // create a builder from env if RUST_LOG exists, otherwise create a default builder
    let mut builder = if env_val.is_empty() {
        env_logger::Builder::new()
    } else {
        env_logger::Builder::from_default_env()
    };

    // set a default filter unless the user has passed a filter using the RUST_LOG env var
    if env_val.is_empty() {
        builder.filter(Some(env!("CARGO_CRATE_NAME")), default_level);
    }

    // if the user has passed RUST_LOG_STYLE, use it, otherwise use our favorite style
    if let Some(style_env_value) = std::env::var(env_logger::DEFAULT_WRITE_STYLE_ENV).ok() {
        builder.parse_write_style(&style_env_value);
    } else {
        builder.format(|buf, record| {
            let level = format!("[{}]", record.level());
            let level = match record.level() {
                Level::Error => level.red(),
                Level::Warn => level.yellow(),
                Level::Info => level.cyan(),
                Level::Debug => level.truecolor(100, 100, 100),
                Level::Trace => level.truecolor(200, 200, 200),
            };
            writeln!(
                buf,
                "{}:{} {} {} - {}",
                record.file().unwrap_or("unknown"),
                record.line().unwrap_or(0),
                chrono::Local::now().format("%Y-%m-%dT%H:%M:%S"),
                level,
                record.args(),
            )
        });
    }
    builder.init()
}