feat: allow manual signal disposal before the scope is disposed (#710)

leptos_reactive/src/memo.rs

@@ -1,8 +1,8 @@
 #![forbid(unsafe_code)]
 use crate::{
     create_effect, node::NodeId, on_cleanup, with_runtime, AnyComputation,
-    RuntimeId, Scope, SignalGet, SignalGetUntracked, SignalStream, SignalWith,
-    SignalWithUntracked,
+    RuntimeId, Scope, SignalDispose, SignalGet, SignalGetUntracked,
+    SignalStream, SignalWith, SignalWithUntracked,
 };
 use std::{any::Any, cell::RefCell, fmt::Debug, marker::PhantomData, rc::Rc};
 
@@ -412,6 +412,12 @@ impl<T: Clone> SignalStream<T> for Memo<T> {
     }
 }
 
+impl<T> SignalDispose for Memo<T> {
+    fn dispose(self) {
+        _ = with_runtime(self.runtime, |runtime| runtime.dispose_node(self.id));
+    }
+}
+
 impl_get_fn_traits![Memo];
 
 pub(crate) struct MemoState<T, F>

leptos_reactive/src/runtime.rs

@@ -254,6 +254,12 @@ impl Runtime {
             }
         });
     }
+
+    pub(crate) fn dispose_node(&self, node: NodeId) {
+        self.node_sources.borrow_mut().remove(node);
+        self.node_subscribers.borrow_mut().remove(node);
+        self.nodes.borrow_mut().remove(node);
+    }
 }
 
 impl Debug for Runtime {

leptos_reactive/src/signal.rs

@@ -274,6 +274,16 @@ pub trait SignalStream<T> {
     fn to_stream(&self, cx: Scope) -> Pin<Box<dyn Stream<Item = T>>>;
 }
 
+/// This trait allows disposing a signal before its [Scope] has been disposed.
+pub trait SignalDispose {
+    /// Disposes of the signal. This:
+    /// 1. Detaches the signal from the reactive graph, preventing it from triggering
+    ///    further updates; and
+    /// 2. Drops the value contained in the signal.
+    #[track_caller]
+    fn dispose(self);
+}
+
 /// Creates a signal, the basic reactive primitive.
 ///
 /// A signal is a piece of data that may change over time,
@@ -725,6 +735,12 @@ impl<T: Clone> SignalStream<T> for ReadSignal<T> {
     }
 }
 
+impl<T> SignalDispose for ReadSignal<T> {
+    fn dispose(self) {
+        _ = with_runtime(self.runtime, |runtime| runtime.dispose_node(self.id));
+    }
+}
+
 impl<T> ReadSignal<T>
 where
     T: 'static,
@@ -1025,6 +1041,12 @@ impl<T> SignalSet<T> for WriteSignal<T> {
     }
 }
 
+impl<T> SignalDispose for WriteSignal<T> {
+    fn dispose(self) {
+        _ = with_runtime(self.runtime, |runtime| runtime.dispose_node(self.id));
+    }
+}
+
 impl<T> Clone for WriteSignal<T> {
     fn clone(&self) -> Self {
         Self {
@@ -1598,6 +1620,12 @@ impl<T: Clone> SignalStream<T> for RwSignal<T> {
     }
 }
 
+impl<T> SignalDispose for RwSignal<T> {
+    fn dispose(self) {
+        _ = with_runtime(self.runtime, |runtime| runtime.dispose_node(self.id));
+    }
+}
+
 impl<T> RwSignal<T> {
     /// Returns a read-only handle to the signal.
     ///