backtrace-error

This is a tiny crate that provides a tiny error-wrapper struct BacktraceError with only two features:

• Captures a backtrace on From-conversion from its wrapped type (if RUST_BACKTRACE is on etc.)
• Pretty-prints that backtrace in its Display implementation.

It also includes an extension trait ResultExt that you can use to give you .unwrap_or_backtrace and .expect_or_backtrace methods on any Result<T, BacktraceError<E>>. These methods do do the same as unwrap or expect on Result except they pretty-print the backtrace on Err, before panicking.

Finally, it provides a dynamic variant in case you want to type-erase the error type, DynBacktraceError. This works the same as BacktraceError<E> but wraps a Box<dyn Error + Send + Sync + 'static> instead of requiring a specific error type E, so is therefore potentially more expensive but also more flexible and usable as an "any error" catchall type since it has an impl<E:Error + Send + Sync + 'static> From<E> conversion.

Example

Usage is straightforward: put some existing error type in it. No macros!

use backtrace_error::{BacktraceError,ResultExt};
use std::{io,fs};

type IOError = BacktraceError<io::Error>;

fn open_file() -> Result<fs::File, IOError> {
   Ok(fs::File::open("/does-not-exist.nope")?)
}

fn do_stuff() -> Result<fs::File, IOError>
{
    open_file()
}

fn main()
{
    // This will panic but first print a backtrace of
    // the error site, then a backtrace of the panic site.
    let file = do_stuff().unwrap_or_backtrace();
}

or dynamically:

use backtrace_error::{DynBacktraceError,ResultExt};
use std::{io,fs};

type AppErr = DynBacktraceError;

fn open_file() -> Result<fs::File, AppErr> {
   Ok(fs::File::open("/does-not-exist.nope")?)
}

fn parse_number() -> Result<i32, AppErr> {
   Ok(i32::from_str_radix("not-a-number", 10)?)
}

fn do_stuff() -> Result<(), AppErr>
{
    open_file()?;
    parse_number()?;
    Ok(())
}

fn main()
{
    // This will panic but first print a backtrace of
    // the error site, then a backtrace of the panic site.
    do_stuff().unwrap_or_backtrace();
}

I am very sorry for having written Yet Another Rust Error Crate but strangely everything I looked at either doesn't capture backtraces, doesn't print them, only debug-prints them on a failed unwrap (which is illegible), provides a pile of features I don't want through expensive macros, or some combination thereof. I don't need any of that, I just want to capture backtraces for errors when they occur, and print them out sometime later.

I figured maybe someone out there has the same need, so am publishing it.

License: MIT OR Apache-2.0