assets/examples/ruby/promises.rb

@@ -1,2 +1,5 @@
-puts get_player_name.await
+a = get_player_name
+b = a
+puts a.await
+puts b.await
 quit

src/callback.rs

@@ -10,18 +10,18 @@ pub struct CallbackSystem<R: Runtime> {
     pub(crate) arg_types: Vec<TypeId>,
 }
 
-pub(crate) struct FunctionCallEvent<C: Send, V: Send> {
+pub(crate) struct FunctionCallEvent<C: Send, V: Send, F: Send> {
     pub(crate) params: Vec<V>,
-    pub(crate) promise: Promise<C, V>,
+    pub(crate) promise: Promise<C, V, F>,
 }
 
-type Calls<C, V> = Arc<Mutex<Vec<FunctionCallEvent<C, V>>>>;
+type Calls<C, V, F> = Arc<Mutex<Vec<FunctionCallEvent<C, V, F>>>>;
 
 /// A struct representing a Bevy system that can be called from a script.
 pub(crate) struct Callback<R: Runtime> {
     pub(crate) name: String,
     pub(crate) system: Arc<Mutex<CallbackSystem<R>>>,
-    pub(crate) calls: Calls<R::CallContext, R::Value>,
+    pub(crate) calls: Calls<R::CallContext, R::Value, R::Value>,
 }
 
 impl<R: Runtime> Clone for Callback<R> {
@@ -37,7 +37,7 @@ impl<R: Runtime> Clone for Callback<R> {
 impl<R: Runtime> CallbackSystem<R> {
     pub(crate) fn call(
         &mut self,
-        call: &FunctionCallEvent<R::CallContext, R::Value>,
+        call: &FunctionCallEvent<R::CallContext, R::Value, R::Value>,
         world: &mut World,
     ) -> R::Value {
         self.system.run(call.params.clone(), world)

src/lib.rs

@@ -345,7 +345,8 @@ pub trait Runtime: Resource + Default {
         f: impl Fn(
             Self::CallContext,
             Vec<Self::Value>,
-        ) -> Result<Promise<Self::CallContext, Self::Value>, ScriptingError>
+        )
+            -> Result<Promise<Self::CallContext, Self::Value, Self::Value>, ScriptingError>
         + Send
         + Sync
         + 'static,

src/promise.rs

@@ -1,27 +1,31 @@
 use std::sync::{Arc, Mutex};
 
+use magnus::Fiber;
+
 use crate::{Runtime, ScriptingError};
 
 /// A struct that represents a function that will get called when the Promise is resolved.
-pub(crate) struct PromiseCallback<C: Send, V: Send> {
+pub(crate) struct PromiseCallback<C: Send, V: Send, F: Send> {
     callback: V,
-    following_promise: Arc<Mutex<PromiseInner<C, V>>>,
+    following_promise: Arc<Mutex<PromiseInner<C, V, F>>>,
 }
 
 /// Internal representation of a Promise.
-pub(crate) struct PromiseInner<C: Send, V: Send> {
+pub(crate) struct PromiseInner<C: Send, V: Send, F: Send> {
-    pub(crate) callbacks: Vec<PromiseCallback<C, V>>,
+    pub(crate) callbacks: Vec<PromiseCallback<C, V, F>>,
     #[allow(deprecated)]
     pub(crate) context: C,
+    pub(crate) resolved_value: Option<V>,
+    pub(crate) fibers: Vec<F>, // TODO: should htis be vec or option
 }
 
 /// A struct that represents a Promise.
 #[derive(Clone)]
-pub struct Promise<C: Send, V: Send> {
+pub struct Promise<C: Send, V: Send, F: Send> {
-    pub(crate) inner: Arc<Mutex<PromiseInner<C, V>>>,
+    pub(crate) inner: Arc<Mutex<PromiseInner<C, V, F>>>,
 }
 
-impl<C: Send, V: Send + Clone> PromiseInner<C, V> {
+impl<C: Send, V: Send + Clone, F: Send + Clone> PromiseInner<C, V, F> {
     /// Resolve the Promise. This will call all the callbacks that were added to the Promise.
     fn resolve<R>(&mut self, runtime: &mut R, val: R::Value) -> Result<(), ScriptingError>
     where
@@ -41,7 +45,7 @@ impl<C: Send, V: Send + Clone> PromiseInner<C, V> {
     }
 }
 
-impl<C: Clone + Send + 'static, V: Send + Clone> Promise<C, V> {
+impl<C: Clone + Send + 'static, V: Send + Clone, F: Send + Clone> Promise<C, V, F> {
     /// Acquire [Mutex] for writing the promise and resolve it. Call will be forwarded to [PromiseInner::resolve].
     pub(crate) fn resolve<R>(
         &mut self,
@@ -52,11 +56,25 @@ impl<C: Clone + Send + 'static, V: Send + Clone> Promise<C, V> {
         R: Runtime<Value = V, CallContext = C>,
     {
         if let Ok(mut inner) = self.inner.lock() {
+            inner.resolved_value = Some(val.clone());
             inner.resolve(runtime, val)?;
+            for fiber in inner.fibers.drain(..) {
+                println!("resume");
+            }
         }
         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: F) {
+        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 +83,10 @@ 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

@@ -129,9 +129,9 @@ impl Drop for RubyThread {
     }
 }
 
-impl DataTypeFunctions for Promise<(), RubyValue> {}
+impl DataTypeFunctions for Promise<(), RubyValue, RubyValue> {}
 
-unsafe impl TypedData for Promise<(), RubyValue> {
+unsafe impl TypedData for Promise<(), RubyValue, RubyValue> {
     fn class(ruby: &Ruby) -> magnus::RClass {
         static CLASS: Lazy<RClass> = Lazy::new(|ruby| {
             let class = ruby
@@ -147,12 +147,12 @@ unsafe impl TypedData for Promise<(), RubyValue> {
 
     fn data_type() -> &'static magnus::DataType {
         static DATA_TYPE: DataType =
-            data_type_builder!(Promise<(), RubyValue>, "Bevy::Promise").build();
+            data_type_builder!(Promise<(), RubyValue, RubyValue>, "Bevy::Promise").build();
         &DATA_TYPE
     }
 }
 
-impl TryConvert for Promise<(), RubyValue> {
+impl TryConvert for Promise<(), RubyValue, RubyValue> {
     fn try_convert(val: magnus::Value) -> Result<Self, magnus::Error> {
         let result: Result<&Self, _> = TryConvert::try_convert(val);
         result.cloned()
@@ -160,7 +160,7 @@ impl TryConvert for Promise<(), RubyValue> {
 }
 
 fn then(r_self: magnus::Value) -> magnus::Value {
-    let promise: &Promise<(), RubyValue> =
+    let promise: &Promise<(), RubyValue, 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");
@@ -179,21 +179,15 @@ fn then(r_self: magnus::Value) -> magnus::Value {
 }
 
 fn await_promise(r_self: magnus::Value) -> magnus::Value {
-    let promise: &Promise<(), RubyValue> =
+    let promise: &Promise<(), RubyValue, 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());
+    let fiber = Opaque::from(ruby.fiber_current().as_value());
-    promise
+    if let Some(value) = &promise.inner.try_lock().unwrap().resolved_value {
-        .clone()
+        panic!();
-        .then(RubyValue::new(
+    }
-            ruby.proc_from_fn(move |ruby, args, _| {
+    promise.clone().await_promise(RubyValue(fiber)).into_value();
-                let fiber = ruby.get_inner(fiber);
-                fiber.resume::<_, magnus::Value>(args).unwrap();
-            })
-            .as_value(),
-        ))
-        .into_value();
     ruby.fiber_yield::<_, magnus::Value>(()).unwrap()
 }
 
@@ -457,7 +451,7 @@ impl Runtime for RubyRuntime {
             Self::CallContext,
             Vec<Self::Value>,
         ) -> Result<
-            crate::promise::Promise<Self::CallContext, Self::Value>,
+            crate::promise::Promise<Self::CallContext, Self::Value, Self::Value>,
             crate::ScriptingError,
         > + Send
         + Sync
@@ -467,9 +461,10 @@ impl Runtime for RubyRuntime {
             dyn Fn(
                     (),
                     Vec<RubyValue>,
-                )
+                ) -> Result<
-                    -> Result<crate::promise::Promise<(), RubyValue>, crate::ScriptingError>
+                    crate::promise::Promise<(), RubyValue, RubyValue>,
-                + Send,
+                    crate::ScriptingError,
+                > + Send,
         >;
         static RUBY_CALLBACKS: LazyLock<Mutex<HashMap<String, CallbackClosure>>> =
             LazyLock::new(|| Mutex::new(HashMap::new()));

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)
@@ -142,7 +144,7 @@ pub(crate) fn process_calls<R: Runtime>(world: &mut World) -> Result<(), Scripti
             .lock()
             .expect("Failed to lock callback calls mutex")
             .drain(..)
-            .collect::<Vec<FunctionCallEvent<R::CallContext, R::Value>>>();
+            .collect::<Vec<FunctionCallEvent<R::CallContext, R::Value, R::Value>>>();
         for mut call in calls {
             tracing::trace!("process_calls: calling '{}'", callback.name);
             let mut system = callback