The aim of this library is to support writing command line programs in Rust by simplifying error handling in program code.

It introduces Problem type which can be used on high level APIs for which error handling boils down to:

• reporting error message (e.g. log with error! macro),
• aborting program on error other than a bug (e.g. using panic! macro),
• ignoring error.

Goals

• Simplifying type signatures around error handling to one type so they compose easily
• Allow errors to bubble up easily by elimination of life times in error types
• Produce user friendly error messages with Display formatting
• Support multiple ways to add context to error message
• Easy to work with existing types and patterns
• No performance impact on Ok path

Non Goals

• Providing ability to match on particular error variant to facilitate handling of error condition
• High performance of Err path - e.g. zero allocation
• Sync and Send compatibility

Example

Implicit conversion to Problem type and context message.

use problem::prelude::*;

fn foo() -> Result<String, Problem> {
    let str = String::from_utf8(vec![0, 123, 255])?;
    Ok(str)
}

let result = foo().problem_while("creating string");

assert_eq!(result.unwrap_err().to_string(), "while creating string got problem caused by: invalid utf-8 sequence of 1 bytes from index 2");

Handling fatal errors with panic and Problem::or_failed_to.

use problem::prelude::*;
use problem::format_panic_to_stderr;

format_panic_to_stderr();

fn foo() -> Result<String, Problem> {
    let str = String::from_utf8(vec![0, 123, 255])?;
    Ok(str)
}

let _s = foo().or_failed_to("create a string"); // Fatal error: Panicked in src/lib.rs:464:25: Failed to create a string due to: invalid utf-8 sequence of 1 bytes from index 2

For more examples see crate documentation at docs.rs.