twyg 0.5.0

A tiny logging setup for Rust applications
Documentation

twyg

A tiny logging setup for Rust applications

I got used to logging my apps in with:

so here's something similar for Rust ;-)

Version warnings:

  • v0.4 - Due to the more complex nature of OwoColors, a major code refactor was required to fix the colour regression of v0.3, and as part of that several breaking changes were introduced, including a struct raname, new fields, etc.
  • v0.3 - A regression was introduced due to the move away from the unsupported (and insecure) colors library whereby one could no longer disable ANSI colour of logged output.

Usage

First, update your Cargo.tomls dependencies section:

[dependencies]
twyg = "0.5"

I like to put my logging setup in YAML config files for my apps, but however you prefer to store your config, you'll next need to create a twyg::Opts using the builder pattern:

use twyg::{LogLevel, OptsBuilder};

let opts = OptsBuilder::new()
    .coloured(true)
    .level(LogLevel::Debug)
    .report_caller(true)
    .build()
    .unwrap();

match twyg::setup(opts) {
    Ok(_) => {},
    Err(error) => {
        panic!("Could not setup logger: {:?}", error)
    },
};

The supported options are:

  • coloured: setting to false will disable ANIS colours in the logging output
  • file: provide a path to a file, and output will be logged there too
  • level: case-insensitive logging level
  • report_caller: setting to true will output the filename and line number where the logging call was made

Once the setup function has been called, all subsequent calls to the standard Rust logging macros will use this setup, providing output like the following:

The output in the screenshot above (click for a full-sized view) is from running the demos in the examples directory.

Config

Use with the config library is seamless thanks to serde support:

  1. Set up some YAML:

    logging:
    coloured: true
    level: debug
    output: stdout
    report_caller: true
    time_format: "%Y-%m-%d %H:%M:%S"

  2. Add an entry to your config struct:

    use serde::Deserialize;

#[derive(Debug, Deserialize)]
pub struct YourAppConfig {
    ...
    pub logging: twyg::Opts,
    ...
}

  3. Create a constructor for YourAppConfig (see config library docs and examples)

  4. Build your config:

    let cfg = YourAppConfig::default().unwrap();

  5. Pass the logging config to twyg:

    match twyg::setup(cfg.logging) {
    Ok(_) => {}
    Err(error) => panic!("Could not setup logger: {error:?}"),
};

Note: The Opts struct uses lowercase serialization for enums ("debug", "info", etc.), so your YAML/JSON config files should use lowercase strings for level and output fields.

Migration Guide

Upgrading from v0.4 to v0.5

v0.5 introduces type-safe enums and a builder pattern for better API ergonomics. Here's how to migrate:

1. Replace stringly-typed level functions with LogLevel enum

Before (v0.4):

use twyg::{self, level};

let opts = twyg::Opts {
    level: level::debug(),
    ...
};

After (v0.5):

use twyg::{LogLevel, OptsBuilder};

let opts = OptsBuilder::new()
    .level(LogLevel::Debug)
    .build()
    .unwrap();

2. Replace stringly-typed output with Output enum

Before (v0.4):

use twyg::{self, out};

let opts = twyg::Opts {
    file: out::stdout(),
    ...
};

After (v0.5):

use twyg::{Output, OptsBuilder};

let opts = OptsBuilder::new()
    .output(Output::Stdout)
    .build()
    .unwrap();

3. Use OptsBuilder instead of struct literals

Before (v0.4):

let opts = twyg::Opts {
    coloured: true,
    level: level::debug(),
    report_caller: true,
    ..Default::default()
};

After (v0.5):

let opts = OptsBuilder::new()
    .coloured(true)
    .level(LogLevel::Debug)
    .report_caller(true)
    .build()
    .unwrap();

4. Error handling now uses custom TwygError

Before (v0.4):

match twyg::setup(&opts) {
    Ok(_) => {},
    Err(error) => { /* anyhow::Error */ },
}

After (v0.5):

match twyg::setup(opts) {
    Ok(_) => {},
    Err(error) => { /* twyg::TwygError with specific variants */ },
}

Backwards Compatibility

The old stringly-typed functions are still available but deprecated:

  • level::debug(), level::info(), etc. → Use LogLevel::Debug, LogLevel::Info
  • out::stdout(), out::stderr() → Use Output::Stdout, Output::Stderr

License

Copyright © 2020-2026, Oxur Group

Apache License, Version 2.0