From 84caa35cef9fb2f87cda791b086e86e7ff1d3865 Mon Sep 17 00:00:00 2001
From: Greg Johnston <greg.johnston@gmail.com>
Date: Mon, 5 May 2025 21:20:34 -0400
Subject: [PATCH] feat: add `.map()` and `.and_then()` on `LocalResource`
 (#3941)

---
 leptos_server/src/local_resource.rs | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/leptos_server/src/local_resource.rs b/leptos_server/src/local_resource.rs
index 3abfae1ab..e518f3f27 100644
--- a/leptos_server/src/local_resource.rs
+++ b/leptos_server/src/local_resource.rs
@@ -300,6 +300,34 @@ impl<T> LocalResource<T> {
     pub fn refetch(&self) {
         self.refetch.try_update(|n| *n += 1);
     }
+
+    /// Synchronously, reactively reads the current value of the resource and applies the function
+    /// `f` to its value if it is `Some(_)`.
+    #[track_caller]
+    pub fn map<U>(&self, f: impl FnOnce(&T) -> U) -> Option<U>
+    where
+        T: 'static,
+    {
+        self.data.try_with(|n| n.as_ref().map(f))?
+    }
+}
+
+impl<T, E> LocalResource<Result<T, E>>
+where
+    T: 'static,
+    E: Clone + 'static,
+{
+    /// Applies the given function when a resource that returns `Result<T, E>`
+    /// has resolved and loaded an `Ok(_)`, rather than requiring nested `.map()`
+    /// calls over the `Option<Result<_, _>>` returned by the resource.
+    ///
+    /// This is useful when used with features like server functions, in conjunction
+    /// with `<ErrorBoundary/>` and `<Suspense/>`, when these other components are
+    /// left to handle the `None` and `Err(_)` states.
+    #[track_caller]
+    pub fn and_then<U>(&self, f: impl FnOnce(&T) -> U) -> Option<Result<U, E>> {
+        self.map(|data| data.as_ref().map(f).map_err(|e| e.clone()))
+    }
 }
 
 impl<T> IntoFuture for LocalResource<T>