Cargo.toml

@@ -35,6 +35,7 @@ magnus = { version = "0.7.1", optional = true }
 rb-sys = { version = "0.9", default-features = false, features = ["link-ruby", "ruby-static"], optional = true }
 crossbeam-channel = "0.5.15"
 libc = "0.2.172"
+tempfile = "3.20.0"
 
 [[example]]
 name = "call_function_from_rust_rhai"

assets/examples/ruby/promises.rb

@@ -1,3 +1,21 @@
-get_player_name.and_then do |name|
+def async_fun
-  puts name
+  async do
+    a = get_player_name
+    b = a
+    puts '0'
+    puts a.await
+    puts '1'
+    u = get_player_name
+    puts b.await
+    puts '2'
+    z = get_player_name
+    puts z
+    puts z.await
+    puts "end"
+  end
 end
+
+async_fun.await
+puts "after await"
+
+quit

examples/ruby/promises.rs

@@ -9,15 +9,19 @@ fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
         .add_scripting::<RubyRuntime>(|builder| {
-            builder.add_function(
+            builder
-                String::from("get_player_name"),
+                .add_function(
-                |player_names: Query<&Name, With<Player>>| {
+                    String::from("get_player_name"),
-                    player_names
+                    |player_names: Query<&Name, With<Player>>| {
-                        .single()
+                        player_names
-                        .expect("Missing player_names")
+                            .single()
-                        .to_string()
+                            .expect("Missing player_names")
-                },
+                            .to_string()
-            );
+                    },
+                )
+                .add_function(String::from("quit"), |mut exit: EventWriter<AppExit>| {
+                    exit.write(AppExit::Success);
+                });
         })
         .add_systems(Startup, startup)
         .run();

src/lib.rs

@@ -375,6 +375,8 @@ pub trait Runtime: Resource + Default {
     fn needs_rdynamic_linking() -> bool {
         false
     }
+
+    fn resume(&self, fiber: &Self::Value, value: &Self::Value);
 }
 
 pub trait FuncArgs<'a, V, R: Runtime> {

src/promise.rs

@@ -13,6 +13,8 @@ pub(crate) struct PromiseInner<C: Send, V: Send> {
     pub(crate) callbacks: Vec<PromiseCallback<C, V>>,
     #[allow(deprecated)]
     pub(crate) context: C,
+    pub(crate) resolved_value: Option<V>,
+    pub(crate) fibers: Vec<V>, // TODO: should htis be vec or option
 }
 
 /// A struct that represents a Promise.
@@ -51,12 +53,31 @@ impl<C: Clone + Send + 'static, V: Send + Clone> Promise<C, V> {
     where
         R: Runtime<Value = V, CallContext = C>,
     {
+        let mut fibers: Vec<V> = vec![];
         if let Ok(mut inner) = self.inner.lock() {
-            inner.resolve(runtime, val)?;
+            inner.resolved_value = Some(val.clone());
+            inner.resolve(runtime, val.clone())?;
+
+            for fiber in inner.fibers.drain(..) {
+                fibers.push(fiber);
+            }
+        }
+        for fiber in fibers {
+            runtime.resume(&fiber, &val.clone());
         }
         Ok(())
     }
 
+    /// Register a fiber that will be resumed when the [Promise] is resolved.
+    #[cfg(any(feature = "rhai", feature = "lua", feature = "ruby"))]
+    pub(crate) fn await_promise(&mut self, fiber: V) {
+        let mut inner = self
+            .inner
+            .lock()
+            .expect("Failed to lock inner promise mutex");
+        inner.fibers.push(fiber);
+    }
+
     /// Register a callback that will be called when the [Promise] is resolved.
     #[cfg(any(feature = "rhai", feature = "lua", feature = "ruby"))]
     pub(crate) fn then(&mut self, callback: V) -> Self {
@@ -65,8 +86,10 @@ impl<C: Clone + Send + 'static, V: Send + Clone> Promise<C, V> {
             .lock()
             .expect("Failed to lock inner promise mutex");
         let following_inner = Arc::new(Mutex::new(PromiseInner {
+            fibers: vec![],
             callbacks: vec![],
             context: inner.context.clone(),
+            resolved_value: None,
         }));
 
         inner.callbacks.push(PromiseCallback {

src/runtimes/ruby.rs

@@ -1,11 +1,16 @@
 use std::{
     collections::HashMap,
     ffi::CString,
+    io::Write,
     sync::{Arc, Condvar, LazyLock, Mutex},
     thread::{self, JoinHandle},
 };
 
-use ::magnus::{typed_data::Inspect, value::Opaque};
+use ::magnus::{
+    Fiber,
+    typed_data::Inspect,
+    value::{self, Opaque},
+};
 use bevy::{
     asset::Asset,
     ecs::{component::Component, entity::Entity, resource::Resource, schedule::ScheduleLabel},
@@ -19,7 +24,7 @@ use magnus::{
     value::{Lazy, ReprValue},
 };
 use magnus::{method, prelude::*};
-use rb_sys::{VALUE, ruby_init_stack};
+use rb_sys::{VALUE, rb_load, ruby_init_stack};
 use serde::Deserialize;
 
 use crate::{
@@ -174,6 +179,19 @@ fn then(r_self: magnus::Value) -> magnus::Value {
         .into_value()
 }
 
+fn await_promise(r_self: magnus::Value) -> magnus::Value {
+    let promise: &Promise<(), RubyValue> =
+        TryConvert::try_convert(r_self).expect("Couldn't convert self to Promise");
+    let ruby =
+        Ruby::get().expect("Failed to get a handle to Ruby API when registering Promise callback");
+    let fiber = Opaque::from(ruby.fiber_current().as_value());
+    if let Some(value) = &promise.inner.try_lock().unwrap().resolved_value {
+        return ruby.get_inner(value.0);
+    }
+    promise.clone().await_promise(RubyValue(fiber)).into_value();
+    ruby.fiber_yield::<_, magnus::Value>(()).unwrap()
+}
+
 #[derive(Clone, Debug)]
 #[magnus::wrap(class = "Bevy::Entity")]
 pub struct BevyEntity(pub Entity);
@@ -195,6 +213,19 @@ impl TryConvert for BevyEntity {
 #[magnus::wrap(class = "Bevy::Vec3")]
 pub struct BevyVec3(pub Vec3);
 
+pub fn async_function() {
+    let ruby = Ruby::get().unwrap();
+    let fiber = ruby
+        .fiber_new_from_fn(Default::default(), move |ruby, _args, _block| {
+            let p = ruby.block_proc().unwrap();
+            p.call::<_, value::Value>(()).unwrap();
+
+            Ok(())
+        })
+        .unwrap();
+    fiber.resume::<_, magnus::Value>(()).unwrap();
+}
+
 impl BevyVec3 {
     pub fn new(x: f32, y: f32, z: f32) -> Self {
         Self(Vec3::new(x, y, z))
@@ -266,12 +297,15 @@ impl Default for RubyRuntime {
 
                 let promise = module.define_class("Promise", ruby.class_object())?;
                 promise.define_method("and_then", magnus::method!(then, 0))?;
+                promise.define_method("await", magnus::method!(await_promise, 0))?;
 
                 let vec3 = module.define_class("Vec3", ruby.class_object())?;
                 vec3.define_singleton_method("new", function!(BevyVec3::new, 3))?;
                 vec3.define_method("x", method!(BevyVec3::x, 0))?;
                 vec3.define_method("y", method!(BevyVec3::y, 0))?;
                 vec3.define_method("z", method!(BevyVec3::z, 0))?;
+
+                ruby.define_global_function("async", function!(async_function, 0));
                 Ok::<(), ScriptingError>(())
             }))
             .expect("Failed to define builtin types");
@@ -392,10 +426,35 @@ impl Runtime for RubyRuntime {
     ) -> Result<Self::ScriptData, crate::ScriptingError> {
         let script = script.0.clone();
         self.execute_in_thread(Box::new(move |ruby: &Ruby| {
-            Self::with_current_entity(ruby, entity, || {
+            let p = Opaque::from(ruby.proc_from_fn(move |ruby, _args, _block| {
-                ruby.eval::<magnus::value::Value>(&script)
+                Self::with_current_entity(ruby, entity, || {
-                    .map_err(<magnus::Error as Into<ScriptingError>>::into)
+                    let mut tmpfile = tempfile::NamedTempFile::new().unwrap();
-            })?;
+                    tmpfile.write(script.as_bytes()).unwrap();
+                    unsafe {
+                        let file = rb_sys::rb_str_new_cstr(
+                            CString::new(tmpfile.path().to_str().unwrap())
+                                .unwrap()
+                                .into_raw(),
+                        );
+                        rb_load(file, 0);
+                    };
+                    // ruby.eval::<magnus::value::Value>(&script)
+                    //     .map_err(<magnus::Error as Into<ScriptingError>>::into)
+                    Ok::<(), ScriptingError>(())
+                })
+                .unwrap();
+            }));
+            let fiber = ruby
+                .fiber_new_from_fn(Default::default(), move |ruby, _args, _block| {
+                    let p = ruby.get_inner(p);
+
+                    p.call::<_, value::Value>(()).unwrap();
+
+                    Ok(())
+                })
+                .unwrap();
+            fiber.resume::<_, value::Value>(()).unwrap();
+
             Ok::<Self::ScriptData, ScriptingError>(RubyScriptData)
         }))
     }
@@ -509,6 +568,15 @@ impl Runtime for RubyRuntime {
     fn needs_rdynamic_linking() -> bool {
         true
     }
+
+    fn resume(&self, fiber: &Self::Value, value: &Self::Value) {
+        let fiber = fiber.clone();
+        let value = value.clone();
+        self.execute_in_thread(move |ruby| {
+            let fiber: Fiber = TryConvert::try_convert(ruby.get_inner(fiber.0)).unwrap();
+            fiber.resume::<_, magnus::Value>((value.0,));
+        });
+    }
 }
 
 pub mod magnus {

src/systems.rs

@@ -89,6 +89,8 @@ pub(crate) fn init_callbacks<R: Runtime>(world: &mut World) -> Result<(), Script
                 move |context, params| {
                     let promise = Promise {
                         inner: Arc::new(Mutex::new(PromiseInner {
+                            resolved_value: None,
+                            fibers: vec![],
                             callbacks: vec![],
                             context,
                         })),
@@ -100,7 +102,7 @@ pub(crate) fn init_callbacks<R: Runtime>(world: &mut World) -> Result<(), Script
                         .expect("Failed to lock callback calls mutex");
 
                     calls.push(FunctionCallEvent {
-                        promise: promise.clone(),
+                        promise: promise.clone(), // TODO: dont clone?
                         params,
                     });
                     Ok(promise)