Error Backtrace

This is a simple crate to debug where your errors are comming from. With the smallest possiable amount of code.

Usage

1. cargo add error-backtrace
2. Add use error_backtrace::{Result, ResultBacktrace}; where you use Result and .backtrace() to backtrace them
3. And add .into() where the error is created. (Compiler will help you with this)
4. Where you read errors use error.inner or *error
5. Use .unwrap on Result to print the backtrace.

Example:

useerror_backtrace::{Result,ResultBacktrace};#[derive(Debug)]struct Error;fn main()-> Result<(),Error>{maybe_error().backtrace()?;Ok(())}fn maybe_error()-> Result<(),Error>{error_source()?;Ok(())}fn error_source()-> Result<(),Error>{Err(Error{}.into())}

Actual real world backtrace!

thread 'main' panicked at crates/vidi-tools/src/bin/camera_getframes.rs:39:65:
called `Result::unwrap()` on an `Err` value: Io(Os { code: 22, kind: InvalidInput, message: "Invalid argument" })
Backtrace:
 0: <core::result::Result<T,F> as core::ops::try_trait::FromResidual<core::result::Result<core::convert::Infallible,E>>>::from_residual
 at /rustc/9fc6b43126469e3858e2fe86cafb4f0fd5068869/library/core/src/result.rs:2009:27
 1: vidi::pipelines::AcquiredCamera::configure
 at /home/rustism/libobscura/crates/vidi/src/pipelines/mod.rs:252:17
 2: vidi::pipelines::AcquiredCamera::configure_pipeline
 at /home/rustism/libobscura/crates/vidi/src/pipelines/mod.rs:282:9
 3: vidi::pipelines::AcquiredCamera::start
 at /home/rustism/libobscura/crates/vidi/src/pipelines/mod.rs:289:9
 4: camera_getframes::main::{{closure}}
 at /home/rustism/libobscura/crates/vidi-tools/src/bin/camera_getframes.rs:39:34
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The message is not wrong, you can get a backtrace using RUST_BACKTRACE=1. But that backtrace only goes down to the .unwrap() call. Meanwhile, this gives you the place where you called .backtrace()

Boxed errors

Example:

useerror_backtrace::{Result,ResultBacktrace,GenericError};useio;usestd::error::Error;fn literal_to_generic()-> std::result::Result<(),GenericError>{lete=io::Error::other("simple");Err(GenericError(Box::new(e)))}fn literal_to_generic_traced()-> Result<(),GenericError>{lete=io::Error::other("simple");Ok(Err(GenericError(Box::new(e)))?)}

Converting between traced errors

The errors are wrapped inside Backtraced<E>, making Result::map_err a bit difficult to use. But there are map_trace methods in ResultBacktrace to make things good again.

usestd::io;useerror_backtrace:{Result,ResultBacktrace};struct MyError(io::Error);implFrom<io::Error>forMyError{fn from(value: io::Error)-> Self{Self(value)}}fn convert(res: Result<(),io::Error>)-> Result<(),MyError>{res.map_trace(MyError::from)}fn convert_into(res: Result<(),io::Error>)-> Result<(),MyError>{res.map_trace_into()}