chainerror/examples/tutorial5.rs

/*!

~~~bash
$ cargo run -q --example tutorial5
Func2 failed because of 'entity not found'
func1 error
~~~

!*/

use chainerror::prelude::*;
use std::error::Error;
use std::io;
use std::result::Result;

fn do_some_io() -> Result<(), Box<Error>> {
    Err(io::Error::from(io::ErrorKind::NotFound))?;
    Ok(())
}

fn func2() -> Result<(), Box<Error>> {
    let filename = "foo.txt";
    do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
    Ok(())
}

fn func1() -> Result<(), Box<Error>> {
    if let Err(e) = func2() {
        if let Some(s) = e.source() {
            eprintln!("func2 failed because of '{}'", s);
            Err(e).map_err(mstrerr!("func1 error"))?;
        }
    }
    Ok(())
}

fn main() -> Result<(), Box<Error>> {
    if let Err(e) = func1() {
        eprintln!("{}", e);
    }
    Ok(())
}