Sleep and async and a debugger?

[TeamDman]

Proposal:

every 20 ticks do
  input from chest
  output stick to dest
  sleep 2 ticks
  output stone to dest
  sleep 2 ticks
  output sand to dest
end

My understanding is that Rust turns async functions into state machines where each resume point becomes a part of the program

async fn bruh() {
  println!("A");
  sleep(2).await;
  println!("B");
  sleep(2).await;
  println!("C");
}

gets turned into

enum ToRun {
  A,
  B,
  C
}
impl ToRun {
  pub fn run(self) {
    match self {
      A => println!("A"),
      B => println!("B"),
      C => println!("C"),
    }
  }
}

Right now, SFM builds an AST and executes it.

If we instead created a SFM virtual machine, it would be easier to distribute the execution of a program over multiple ticks.

This would make sleep and a line-by-line debugger easier to implement.

Cancellation safety / what happens if the chunk is unloaded before the program finishes?

0 every 20 ticks do
1   input 16 from src
2  output 5 to dest1
3  output to dest2
4 end

if there is a reload between 2 and 3, we would need to store the tracker information that tells us how much src has moved already.
Additionally, if 3 is the next statement to be executed, the program would have to reconstruct the input statement which is a memory of limited input slots, not itemstacks themselves.

If the "src" chest has slot 0 changed from 64x stick to 64x stone, when executing 3 after a reload it would complete the actions using the same slots and stuff.

Considering that we care about performance, having the option to pick either execution method and A/B test for speed would be nice.
Direct AST execution may be faster than calling program.tick() until returns done

If we have the SFM-VM break up complex operations into a simple instruction set, we could have a max instructions-executed-without-yielding config to prevent abuse of SFM to consume server resources.

Stack based VM?

[TeamDman]

register-based VM?

leddoo - are stack based vms really slower?

Rust Foundation - Rain: "Cancelling Async Rust" | RustConf 2025

TigerBeetle - Building a Distributed Protocol by Dominik Tornow

or just use raw java vm idk

[TeamDman]

if the game shuts down part way and then sfm updates and the intermediate representation of the program changes that will suck