expect-exit: display an error message and exit without a panic

The expect-exit library defines the Expected trait and implements it for the standard Result enum so that a program can display an error message and exit with a non-zero exit code without invoking a Rust panic, yet optionally unwinding the stack so that various objects may perform some clean-up actions.

Functions

• exit_unwind(code): unwind the stack and exit with the specified code
• exit(msg): display a message and exit with code 1
• exit_perror(msg, err): display a message and the error itself and exit with code 1
• die(msg): the same as exit(), but do not unwind the stack
• die_perror(msg, err): the same as exit_perror(), but do not unwind the stack

Traits

• Expected: declare two methods:

  • expect_or_exit(msg): display the message and exit if the expectation is not met
  • expect_or_die(msg): the same as expect_or_exit(), but do not unwind the stack

• ExpectedWithError: declare two additional methods:

  • expect_or_exit_perror(msg): display the message and an appropriate error description and exit if the expectation is not met
  • expect_or_die_perror(msg): the same as expect_or_exit_perror(), but do not unwind the stack

• ExpectedResult: declare two additional methods:

  • expect_result(msg): return a boxed error result with an appropriate error message if the expectation is not met
  • expect_result_nb(msg): the same as expect_result(), but the error result is not boxed

• an implementation of the Expected and ExpectedResult traits for the standard Option enum

• an implementation of the Expected, ExpectedWithError, and ExpectedResult traits for the standard Result enum

Example

use expect_exit::{Expected, ExpectedResult};

fn get_env_var(name: &str) -> String {
    env::var(name).expect_or_exit(&format!("{} not specified in the environment", name))
}

fn parse_and_handle() -> Result<i32, Box<dyn error::Error>> {
    let config = parse().expect_result("Could not parse the config")?;
    Ok(config.value + 1)
}