toobad

Want better error handling? Well, toobad.

toobad is a simple, unbloated error handling library for Rust.

cargo add toobad

[dependencies]
toobad = "0.1"

The Basics

Any error type automatically converts into toobad::Error via ?:

use toobad::Result;

fn read_config() -> Result<String> {
    let content = std::fs::read_to_string("config.toml")?;
    Ok(content)
}

Adding Context

Wrap any Result or Option with a human-readable message:

use toobad::{Context, Result};

fn read_config() -> Result<String> {
    let content = std::fs::read_to_string("config.toml")
        .context("failed to read config file")?;
    Ok(content)
}

Prints as:

failed to read config file: No such file or directory (os error 2)

Works on Option too:

let value = some_map.get("key").context("key not found")?;

Creating Errors from Scratch

Use the toobad!() macro with full format!() support:

use toobad::toobad;

return Err(toobad!("expected {} items but got {}", expected, actual));

Or bail early with bail!():

use toobad::bail;

bail!("expected {} items but got {}", expected, actual);
// equivalent to: return Err(toobad!(...))

Or assert conditions with ensure!():

use toobad::ensure;

ensure!(x > 0, "x must be positive, got {}", x);
// equivalent to: if !condition { bail!(...) }

Downcasting

Recover the original error type when you need it:

if let Some(io_err) = error.downcast::<std::io::Error>() {
    match io_err.kind() {
        std::io::ErrorKind::NotFound => { /* handle missing file */ }
        _ => { /* handle other io errors */ }
    }
}

License