run_system commands silently fail

[gwafotapa]

While migrating to 16.0, I realized that run_system and run_system_with commands fail silently when passed a system returning a Result. You don't even get a warning. The command just does nothing.

[hukasu]

can you make a minimum reproduction?

[gwafotapa]

My bad. It does emit a warning. I had wrongly configured my logger. The warning is strange though. It says the system tried to recursively run itself. Here is the minimal reproduction:

use bevy::{ecs::system::SystemId, platform::collections::HashMap, prelude::*};

#[derive(Eq, PartialEq, Hash)]
pub enum OneShotSystem {
    Hello,
    PrintMessage,
}

#[derive(Resource, Deref)]
pub struct Callbacks(pub HashMap<OneShotSystem, Entity>);

impl FromWorld for Callbacks {
    fn from_world(world: &mut World) -> Self {
        Self(HashMap::from([
            (OneShotSystem::Hello, world.register_system(hello).entity()),
            (
                OneShotSystem::PrintMessage,
                world.register_system(print_message).entity(),
            ),
        ]))
    }
}

fn hello() -> Result {
    println!("Hello");
    Ok(())
}

fn print_message(In(message): In<&str>) -> Result {
    println!("{}", message);
    Ok(())
}

fn run_hello(callbacks: Res<Callbacks>, mut commands: Commands) {
    commands.run_system(SystemId::from_entity(callbacks[&OneShotSystem::Hello]));
}

fn run_print_message(callbacks: Res<Callbacks>, mut commands: Commands) {
    commands.run_system_with(
        SystemId::<In<&str>>::from_entity(callbacks[&OneShotSystem::PrintMessage]),
        "Goodbye",
    );
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .init_resource::<Callbacks>()
        .add_systems(Startup, (run_hello, run_print_message))
        .run();
}

[hukasu]

ok, found it, you have SystemId::<(), bevy::prelude::Result> but commands.run_system only take in SystemId::<(), ()>, and when it tries to look for RegisteredSystem<(), ()> it can't find it, and errors with the Recursive error, which is not informative for the current case

[gwafotapa]

Yes. I had realized that run_system and run_system_with would only take a system with output (). My issue was with them failing silently not why. As it turns out they don't but you had me catch another error I had with my logger so thank you!

As for the warning not being informative, at least it's pointing to the right place.

[hukasu]

made a PR to improve the error message