From a9ce60843353299c44827ac340f6092ec3bab93a Mon Sep 17 00:00:00 2001
From: Greg Johnston <greg.johnston@gmail.com>
Date: Mon, 13 Jan 2025 21:32:08 -0500
Subject: [PATCH] fix: do not use stale values in AsyncDerived if it is mutated
 before running (#3475)

---
 leptos_macro/src/view/mod.rs                  |  2 +-
 .../async_derived/arc_async_derived.rs        | 21 ++++++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/leptos_macro/src/view/mod.rs b/leptos_macro/src/view/mod.rs
index 02428d5283..0ea12cdd92 100644
--- a/leptos_macro/src/view/mod.rs
+++ b/leptos_macro/src/view/mod.rs
@@ -1651,7 +1651,7 @@ pub(crate) fn ident_from_tag_name(tag_name: &NodeName) -> Ident {
             .path
             .segments
             .iter()
-            .last()
+            .next_back()
             .map(|segment| segment.ident.clone())
             .expect("element needs to have a name"),
         NodeName::Block(_) => {
diff --git a/reactive_graph/src/computed/async_derived/arc_async_derived.rs b/reactive_graph/src/computed/async_derived/arc_async_derived.rs
index 93a8672946..77079d0f60 100644
--- a/reactive_graph/src/computed/async_derived/arc_async_derived.rs
+++ b/reactive_graph/src/computed/async_derived/arc_async_derived.rs
@@ -272,7 +272,10 @@ macro_rules! spawn_derived {
                 // so that the correct value is set synchronously
                 let initial = initial_fut.as_mut().now_or_never();
                 match initial {
-                    None => (false, Some(initial_fut)),
+                    None => {
+                        inner.write().or_poisoned().notifier.notify();
+                        (false, Some(initial_fut))
+                    }
                     Some(orig_value) => {
                         let mut guard = this.inner.write().or_poisoned();
 
@@ -296,10 +299,6 @@ macro_rules! spawn_derived {
         if was_ready {
             first_run.take();
         }
-        // begin loading eagerly but asynchronously, if not already loaded
-        if !was_ready {
-            any_subscriber.mark_dirty();
-        }
 
         if let Some(source) = $source {
             any_subscriber.with_observer(|| source.track());
@@ -312,6 +311,18 @@ macro_rules! spawn_derived {
                 let wakers = Arc::downgrade(&this.wakers);
                 let loading = Arc::downgrade(&this.loading);
                 let fut = async move {
+                    // if the AsyncDerived has *already* been marked dirty (i.e., one of its
+                    // sources has changed after creation), we should throw out the Future
+                    // we already created, because its values might be stale
+                    let already_dirty = inner.upgrade()
+                        .as_ref()
+                        .and_then(|inner| inner.read().ok())
+                        .map(|inner| inner.state == AsyncDerivedState::Dirty)
+                        .unwrap_or(false);
+                    if already_dirty {
+                        initial_fut.take();
+                    }
+
                     while rx.next().await.is_some() {
                         let update_if_necessary = if $should_track {
                             any_subscriber