error-stack -- A context-aware error library with abritrary attached user data

Also check out our [announcement post] for error-stack!

error-stack is an error-handling library centered around the idea of building a Report of the error as it propagates:

```rust use std::fmt;

use error_stack::{Context, IntoReport, Report, Result, ResultExt};

[derive(Debug)]

struct ParseExperimentError;

impl fmt::Display for ParseExperimentError { fn fmt(&self, fmt: &mut fmt::Formatter<'>) -> fmt::Result { fmt.writestr("invalid experiment description") } }

impl Context for ParseExperimentError {}

fn parseexperiment(description: &str) -> Result<(u64, u64), ParseExperimentError> { let value = description .parse() .report() .attachprintablelazy(|| format!("{description:?} could not be parsed as experiment")) .changecontext(ParseExperimentError)?;

Ok((value, 2 * value))

}

[derive(Debug)]

struct ExperimentError;

impl fmt::Display for ExperimentError { fn fmt(&self, fmt: &mut fmt::Formatter<'>) -> fmt::Result { fmt.writestr("Experiment error: Could not run experiment") } }

impl Context for ExperimentError {}

fn startexperiments( experimentids: &[usize], experimentdescriptions: &[&str], ) -> Result, ExperimentError> { let experiments = experimentids .iter() .map(|expid| { let description = experimentdescriptions.get(*expid).okorelse(|| { Report::new(ExperimentError) .attachprintable(format!("Experiment {exp_id} has no valid description")) })?;

        let experiment = parse_experiment(description)
            .attach_printable(format!("Experiment {exp_id} could not be parsed"))
            .change_context(ExperimentError)?;

        Ok(move || experiment.0 * experiment.1)
    })
    .collect::<Result<Vec<_>, ExperimentError>>()
    .attach_printable("Unable to setup experiments")?;

Ok(experiments.iter().map(|experiment| experiment()).collect())

}

fn main() -> Result<(), ExperimentError> { let experimentids = &[0, 2]; let experimentdescriptions = &["10", "20", "3o"]; startexperiments(experimentids, experiment_descriptions)?;

Ok(())

} ```

This will most likely result in an error and print

```text Error: Experiment error: Could not run experiment at examples/demo.rs:54:18 - Unable to setup experiments

Caused by: 0: invalid experiment description at examples/demo.rs:24:10 - Experiment 2 could not be parsed 1: invalid digit found in string at examples/demo.rs:22:10 - "3o" could not be parsed as experiment

```

Please see the [documentation] for a full description.