Allow non-zero exit codes with Application::shutdown()

[simonsan]

Currently, shutdown always returns 0 as exit code:

abscissa/core/src/application.rs

Lines 160 to 169 in 31bdced

	/// Shut down this application gracefully, exiting with success.
	fn shutdown(&self, shutdown: Shutdown) -> ! {
	let components = self.state().components();
	if let Err(e) = components.shutdown(self, shutdown) {
	fatal_error(self, &e)
	}
	process::exit(0);
	}

As a user of abscissa I would expect the following to return a non-zero exit code, when I pass Shutdown::Crash, though.

 if let Err(err) = self.inner_run() {
            status_err!("{}", err);
            APP.shutdown(Shutdown::Crash);
        };

What's the opinion on changing that, to allow non-zero exit codes? We could directly return and call process::exit() ourselves, for sure. I'm unsure, though, whether it wouldn't be nice to stay within abscissa to let all the other components shutting down gracefully, while still exiting with a non-zero exit code.

EDIT:

Maybe utilizing https://docs.rs/exitcode/1.1.2/exitcode/ these numbers?

 /// Shut down this application gracefully, exiting with your given `exit_code`. 
 fn shutdown_with_exit_code(&self, shutdown: Shutdown, exit_code: i32) -> ! { 
     let components = self.state().components(); 
  
     if let Err(e) = components.shutdown(self, shutdown) { 
         fatal_error(self, &e) 
     }; 
   
     process::exit(exit_code); 
 }

[aawsome]

Any news on this?

[simonsan]

@tony-iqlusion No stress, but it would be really awesome if there would be a new patch release (if applicable) for this, so we can use this in rustic and backups don't fail silently in scripts any more. The workaround would need to manually exit in a lot of places. :/

[tony-iqlusion]

There are some additional changes I'd like to make first, but I will try to get another release out soon

[simonsan]

There are some additional changes I'd like to make first, but I will try to get another release out soon

Great, thank you! <3 Anything oneself can/you need help with?

[aawsome]

Don't want to put any pressure. Just wanted to mention that a release would help us to close an high-priority issue in https://github.com/rustic-rs/rustic