Crate easy_error

Easy-error

This crate is a lightweight error handling library meant to play well with the standard Error trait. It is designed for quick prototyping or for Command-line applications where any error will simply bubble up to the user. There are four major components of this crate:

1. A basic, string-based error type that is meant for either quick prototyping or human-facing errors.
2. A nice way to iterate over the causes of an error.
3. Some macros that make returning errors slightly more ergonomic.
4. A “termination” type that produces nicely formatted error messages when returned from the main function.

Rust Version Requirements

The current version requires Rustc 1.46 or newer. In general, this crate will be compilable with the Rustc version available on the oldest supported Ubuntu LTS release. Any change that requires a newer version of Rustc than what is available on the oldest supported Ubuntu LTS will be considered a breaking change.

Example

use std::{fs::File, io::Read};
use easy_error::{bail, ensure, Error, ResultExt, Terminator};

fn from_file() -> Result<i32, Error> {
    let file_name = "example.txt";
    let mut file = File::open(file_name).context("Could not open file")?;

    let mut contents = String::new();
    file.read_to_string(&mut contents).context("Unable to read file")?;

    contents.trim().parse().context("Could not parse file")
}

fn validate(value: i32) -> Result<(), Error> {
    ensure!(value > 0, "Value must be greater than zero (found {})", value);

    if value % 2 == 1 {
        bail!("Only even numbers can be used");
    }

    Ok(())
}

fn main() -> Result<(), Terminator> {
    let value = from_file().context("Unable to get value from file")?;
    validate(value).context("Value is not acceptable")?;

    println!("Value = {}", value);
    Ok(())
}

Macros

• bail
  Exits a function early with an Error.
• ensure
  Exits a function early with an Error if the condition is not satisfied.
• format_err
  Creates an Error using the standard string interpolation syntax.

Structs

• Causes
  An iterator over the causes of an error.
• Error
  An error that is a human-targetted string plus an optional cause.
• Terminator
  An error that wraps all other error types for a nicer debug output.

Traits

• ErrorExt
  Extension methods to Error types.
• ResultExt
  Extension methods to the Result type.

Functions

• err_msg
  Creates an error message from the provided string.

Type Aliases

• Result