chainerror

chainerror provides an error backtrace without doing a real backtrace, so even after you strip your binaries, you still have the error backtrace.

Having nested function returning errors, the output doesn't tell where the error originates from.

```rust use std::path::PathBuf;

type BoxedError = Box; fn readconfigfile(path: PathBuf) -> Result<(), BoxedError> { // do stuff, return other errors let buf = std::fs::readto_string(&path)?; // do stuff, return other errors Ok(()) }

fn processconfigfile() -> Result<(), BoxedError> { // do stuff, return other errors let buf = readconfig_file("foo.txt".into())?; // do stuff, return other errors Ok(()) }

fn main() { if let Err(e) = processconfigfile() { eprintln!("Error:\n{:?}", e); } } ```

This gives the output: console Error: Os { code: 2, kind: NotFound, message: "No such file or directory" } and you have no idea where it comes from.

With chainerror, you can supply a context and get a nice error backtrace:

```rust use chainerror::Context as _; use std::path::PathBuf;

type BoxedError = Box; fn readconfigfile(path: PathBuf) -> Result<(), BoxedError> { // do stuff, return other errors let buf = std::fs::readto_string(&path).context(format!("Reading file: {:?}", &path))?; // do stuff, return other errors Ok(()) }

fn processconfigfile() -> Result<(), BoxedError> { // do stuff, return other errors let buf = readconfig_file("foo.txt".into()).context("read the config file")?; // do stuff, return other errors Ok(()) }

fn main() { if let Err(e) = processconfigfile() { eprintln!("Error:\n{:?}", e); } } ```

with the output: console Error: examples/simple.rs:14:51: read the config file Caused by: examples/simple.rs:7:47: Reading file: "foo.txt" Caused by: Os { code: 2, kind: NotFound, message: "No such file or directory" }

chainerror uses .source() of std::error::Error along with #[track_caller] and Location to provide a nice debug error backtrace. It encapsulates all types, which have Display + Debug and can store the error cause internally.

Along with the Error<T> struct, chainerror comes with some useful helper macros to save a lot of typing.

chainerror has no dependencies!

Debug information is worth it!

Multiple Output Formats

chainerror supports multiple output formats, which can be selected with the different format specifiers:

• {}: Display console func1 error calling func2

• {:#}: Alternative Display console func1 error calling func2 Caused by: func2 error: calling func3 Caused by: (passed error) Caused by: Error reading 'foo.txt' Caused by: entity not found

• {:?}: Debug ```console examples/example.rs:50:13: func1 error calling func2 Caused by: examples/example.rs:25:13: Func2Error(func2 error: calling func3) Caused by: examples/example.rs:18:13: (passed error) Caused by: examples/example.rs:13:18: Error reading 'foo.txt' Caused by: Kind(NotFound)

```

• {:#?}: Alternative Debug console Error<example::Func1Error> { occurrence: Some( "examples/example.rs:50:13", ), kind: func1 error calling func2, source: Some( Error<example::Func2Error> { occurrence: Some( "examples/example.rs:25:13", ), kind: Func2Error(func2 error: calling func3), source: Some( Error<chainerror::AnnotatedError> { occurrence: Some( "examples/example.rs:18:13", ), kind: (passed error), source: Some( Error<alloc::string::String> { occurrence: Some( "examples/example.rs:13:18", ), kind: "Error reading 'foo.txt'", source: Some( Kind( NotFound, ), ), }, ), }, ), }, ), }

Tutorial

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License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.