Queue effects to run after flush_sync

examples/memo_chain.rs

@@ -6,7 +6,7 @@ fn main() {
 
 fn app() -> Element {
     let mut state = use_signal(|| 0);
-    let mut depth = use_signal(|| 1 as usize);
+    let mut depth = use_signal(|| 0 as usize);
     let mut items = use_memo(move || (0..depth()).map(|f| f as _).collect::<Vec<isize>>());
 
     let a = use_memo(move || state() + 1);
@@ -35,14 +35,14 @@ fn Child(
         return None;
     }
 
-    println!("rendering child: {}", depth());
-
     // These memos don't get re-computed when early returns happen
     // In dioxus futures spawned with use_future won't progress if they don't get hit during rendering
     let state = use_memo(move || state() + 1);
-    let item = use_memo(move || items()[dbg!(depth()) - 1]);
+    let item = use_memo(move || items()[depth()]);
     let depth = use_memo(move || depth() - 1);
 
+    println!("rendering child: {}", depth());
+
     rsx! {
         h3 { "Depth({depth})-Item({item}): {state}"}
         Child {

packages/core/src/global_context.rs

@@ -71,7 +71,7 @@ pub fn spawn_forever(fut: impl Future<Output = ()> + 'static) -> Option<Task> {
 ///
 /// This drops the task immediately.
 pub fn remove_future(id: Task) {
-    Runtime::with_current_scope(|cx| cx.remove_future(id));
+    Runtime::with(|rt| rt.remove_task(id)).expect("Runtime to exist");
 }
 
 /// Store a value between renders. The foundational hook for all other hooks.
@@ -94,7 +94,6 @@ pub fn use_hook<State: Clone + 'static>(initializer: impl FnOnce() -> State) ->
     Runtime::with_current_scope(|cx| cx.use_hook(initializer)).expect("to be in a dioxus runtime")
 }
 
-
 /// Get the current render since the inception of this component
 ///
 /// This can be used as a helpful diagnostic when debugging hooks/renders, etc
@@ -217,7 +216,6 @@ pub fn use_drop<D: FnOnce() + 'static>(destroy: D) {
     });
 }
 
-
 /// Push a function to be run before the next render
 /// This is a hook and will always run, so you can't unschedule it
 /// Will run for every progression of suspense, though this might change in the future

packages/core/src/scope_context.rs

@@ -234,13 +234,6 @@ impl Scope {
         Runtime::with(|rt| rt.spawn(self.id, fut)).expect("Runtime to exist")
     }
 
-    /// Informs the scheduler that this task is no longer needed and should be removed.
-    ///
-    /// This drops the task immediately.
-    pub fn remove_future(&self, id: Task) {
-        Runtime::with(|rt| rt.remove_task(id)).expect("Runtime to exist");
-    }
-
     /// Mark this component as suspended and then return None
     pub fn suspend(&self) -> Option<Element> {
         self.suspended.set(true);

packages/core/src/tasks.rs

@@ -45,12 +45,19 @@ impl Task {
         Runtime::with(|rt| !rt.tasks.borrow()[self.0].active.get()).unwrap_or_default()
     }
 
+    pub fn wake(&self) {
+        Runtime::with(|rt| _ = rt.sender.unbounded_send(SchedulerMsg::TaskNotified(*self)));
+    }
+
+    pub fn set_active(&self, active: bool) {
+        Runtime::with(|rt| rt.tasks.borrow()[self.0].active.set(active));
+    }
+
     /// Resume the task.
     pub fn resume(&self) {
         Runtime::with(|rt| {
             // set the active flag, and then ping the scheduler to ensure the task gets queued
-            rt.tasks.borrow()[self.0].active.set(true);
-            _ = rt.sender.unbounded_send(SchedulerMsg::TaskNotified(*self));
+            let was_active = rt.tasks.borrow()[self.0].active.replace(true);
         });
     }
 }

packages/hooks/src/lib.rs

@@ -55,6 +55,9 @@ macro_rules! to_owned {
     };
 }
 
+mod use_callback;
+pub use use_callback::*;
+
 mod use_on_destroy;
 pub use use_on_destroy::*;
 

packages/hooks/src/use_callback.rs

@@ -0,0 +1,48 @@
+use dioxus_core::prelude::use_hook;
+use dioxus_signals::CopyValue;
+use dioxus_signals::Writable;
+
+/// A callback that's always current
+///
+/// Whenever this hook is called the inner callback will be replaced with the new callback but the handle will remain.
+///
+/// There is *currently* no signal tracking on the Callback so anything reading from it will not be updated.
+///
+/// This API is in flux and might not remain.
+pub fn use_callback<O>(f: impl FnMut() -> O + 'static) -> UseCallback<O> {
+    // Create a copyvalue with no contents
+    // This copyvalue is generic over F so that it can be sized properly
+    let mut inner = use_hook(|| CopyValue::new(None));
+
+    // Every time this hook is called replace the inner callback with the new callback
+    inner.set(Some(f));
+
+    // And then wrap that callback in a boxed callback so we're blind to the size of the actual callback
+    use_hook(|| UseCallback {
+        inner: CopyValue::new(Box::new(move || {
+            inner.with_mut(|f: &mut Option<_>| f.as_mut().unwrap()())
+        })),
+    })
+}
+
+/// This callback is not generic over a return type so you can hold a bunch of callbacks at once
+///
+/// If you need a callback that returns a value, you can simply wrap the closure you pass in that sets a value in its scope
+#[derive(PartialEq)]
+pub struct UseCallback<O: 'static + ?Sized> {
+    inner: CopyValue<Box<dyn FnMut() -> O>>,
+}
+
+impl<O: 'static + ?Sized> Clone for UseCallback<O> {
+    fn clone(&self) -> Self {
+        Self { inner: self.inner }
+    }
+}
+// impl<O: 'static> Copy for UseCallback<O> {}
+
+impl<O> UseCallback<O> {
+    /// Call the callback
+    pub fn call(&mut self) -> O {
+        self.inner.with_mut(|f| f())
+    }
+}

packages/hooks/src/use_future.rs

@@ -1,62 +1,67 @@
 #![allow(missing_docs)]
 use dioxus_core::{
-    prelude::{spawn, use_drop, use_hook},
+    prelude::{spawn, use_before_render, use_drop, use_hook},
     ScopeState, Task,
 };
 use dioxus_signals::*;
+use dioxus_signals::{Readable, Writable};
 use futures_util::{future, pin_mut, FutureExt};
 use std::{any::Any, cell::Cell, future::Future, pin::Pin, rc::Rc, sync::Arc, task::Poll};
 
+use crate::use_callback;
+
 /// A hook that allows you to spawn a future
 ///
-/// Does not regenerate the future when dependencies change. If you're looking for a future that does, check out
-/// `use_resource` instead.
+/// Does not regenerate the future when dependencies change.
 pub fn use_future<F>(mut future: impl FnMut() -> F) -> UseFuture
 where
     F: Future + 'static,
 {
-    let mut state = use_signal(|| UseFutureState::Pending);
+    let state = use_signal(|| UseFutureState::Pending);
 
-    let task = use_signal(|| {
-        // Create the user's task
+    // Create the task inside a copyvalue so we can reset it in-place later
+    let task = use_hook(|| {
         let fut = future();
+        CopyValue::new(spawn(async move {
+            fut.await;
+        }))
+    });
 
-        // Spawn a wrapper task that polls the innner future and watch its dependencies
-        let task = spawn(async move {
-            // move the future here and pin it so we can poll it
-            let fut = fut;
-            pin_mut!(fut);
+    /*
+    Early returns in dioxus have consequences for use_memo, use_resource, and use_future, etc
+    We *don't* want futures to be running if the component early returns. It's a rather weird behavior to have
+    use_memo running in the background even if the component isn't hitting those hooks anymore.
 
-            let res = future::poll_fn(|cx| {
-                // Set the effect stack properly
+    React solves this by simply not having early returns interleave with hooks.
+    However, since dioxus allows early returns (since we use them for suspense), we need to solve this problem.
 
-                // Poll the inner future
-                let ready = fut.poll_unpin(cx);
 
-                // add any dependencies to the effect stack that we need to watch when restarting the future
+     */
+    // Track if this *current* render is the same
+    let gen = use_hook(|| CopyValue::new((0, 0)));
 
-                ready
-            })
-            .await;
+    // Early returns will pause this task, effectively
+    use_before_render(move || {
+        gen.write().0 += 1;
+        task.peek().set_active(false);
+    });
 
-            // Set the value
-            // value.set(Some(res));
-        });
+    // However when we actually run this component, we want to resume the task
+    task.peek().set_active(true);
+    gen.write().1 += 1;
 
-        Some(task)
-    });
+    // if the gens are different, we need to wake the task
+    if gen().0 != gen().1 {
+        task.peek().wake();
+    }
 
-    use_drop(move || {
-        if let Some(task) = task.take() {
-            task.stop();
-        }
-    });
+    use_drop(move || task.peek().stop());
 
     UseFuture { task, state }
 }
 
 pub struct UseFuture {
-    task: Signal<Option<Task>>,
+    task: CopyValue<Task>,
     state: Signal<UseFutureState>,
 }
 

packages/signals/src/effect.rs

@@ -2,7 +2,7 @@ use crate::write::*;
 use core::{self, fmt::Debug};
 use dioxus_core::prelude::*;
 use futures_channel::mpsc::UnboundedSender;
-use futures_util::StreamExt;
+use futures_util::{future::Either, pin_mut, StreamExt};
 use generational_box::GenerationalBoxId;
 use parking_lot::RwLock;
 use rustc_hash::FxHashMap;
@@ -52,14 +52,38 @@ pub(crate) fn get_effect_ref() -> EffectStackRef {
         None => {
             let (sender, mut receiver) = futures_channel::mpsc::unbounded();
             spawn_forever(async move {
-                while let Some(id) = receiver.next().await {
+                let mut queued_memos = Vec::new();
+
+                loop {
+                    // Wait for a flush
+                    // This gives a chance for effects to be updated in place and memos to compute their values
+                    let flush_await = flush_sync();
+                    pin_mut!(flush_await);
+
+                    loop {
+                        let res =
+                            futures_util::future::select(&mut flush_await, receiver.next()).await;
+
+                        match res {
+                            Either::Right((_queued, _)) => {
+                                if let Some(task) = _queued {
+                                    queued_memos.push(task);
+                                }
+                                continue;
+                            }
+                            Either::Left(_flushed) => break,
+                        }
+                    }
+
                     EFFECT_STACK.with(|stack| {
-                        let effect_mapping = stack.effect_mapping.read();
-                        if let Some(mut effect) = effect_mapping.get(&id).copied() {
-                            tracing::trace!("Rerunning effect: {:?}", id);
-                            effect.try_run();
-                        } else {
-                            tracing::trace!("Effect not found: {:?}", id);
+                        for id in queued_memos.drain(..) {
+                            let effect_mapping = stack.effect_mapping.read();
+                            if let Some(mut effect) = effect_mapping.get(&id).copied() {
+                                tracing::trace!("Rerunning effect: {:?}", id);
+                                effect.try_run();
+                            } else {
+                                tracing::trace!("Effect not found: {:?}", id);
+                            }
                         }
                     });
                 }