this wasn't a bad idea, but I should implement it correctly

behavior either...

.github/workflows/autofix.yml

@@ -18,7 +18,7 @@ jobs:
   autofix:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with: {toolchain: "nightly-2025-07-16", components: "rustfmt, clippy", target: "wasm32-unknown-unknown", rustflags: ""}
       - name: Install Glib

.github/workflows/ci.yml

@@ -63,6 +63,6 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y libglib2.0-dev
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Semver Checks
         uses: obi1kenobi/cargo-semver-checks-action@v2

.github/workflows/get-example-changed.yml

@@ -19,7 +19,7 @@ jobs:
       matrix: ${{ steps.set-example-changed.outputs.matrix }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Get example files that changed

.github/workflows/get-examples-matrix.yml

@@ -17,7 +17,7 @@ jobs:
       EXCLUDED_EXAMPLES: cargo-make
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install jq
         run: sudo apt-get install jq
       - name: Set Matrix

.github/workflows/get-leptos-changed.yml

@@ -13,7 +13,7 @@ jobs:
       leptos_changed: ${{ steps.set-source-changed.outputs.leptos_changed }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Get source files that changed

.github/workflows/get-leptos-matrix.yml

@@ -13,7 +13,7 @@ jobs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install jq
         run: sudo apt-get install jq
       - name: Set Matrix

.github/workflows/publish-book.yml

@@ -12,7 +12,7 @@ jobs:
       contents: write # To push a branch
       pull-requests: write # To create a PR from that branch
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Install mdbook

.github/workflows/run-cargo-make-task.yml

@@ -53,7 +53,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y libglib2.0-dev
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Setup Rust
         uses: dtolnay/rust-toolchain@master
         with:

examples/axum_js_ssr/Cargo.toml

@@ -27,7 +27,7 @@ tokio = { version = "1.39", features = [
 ], optional = true }
 tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }
-wasm-bindgen = "0.2.92"
+wasm-bindgen = "0.2.105"
 web-sys = { version = "0.3.69", features = [
   "AddEventListenerOptions",
   "Document",

examples/axum_js_ssr/src/app.rs

@@ -510,11 +510,9 @@ if (window.hljs) {
             });
             view! {
                 <pre><code class="language-rust">{code.await}</code></pre>
-                {
-                    move || script.get().map(|script| {
-                        view! { <Script>{script}</Script> }
-                    })
-                }
+                <ShowLet some=script let:script>
+                    <Script>{script}</Script>
+                </ShowLet>
             }
         })
     };
@@ -567,11 +565,9 @@ if (window.hljs) {
             });
             view! {
                 <pre><code class="language-rust">{code.await}</code></pre>
-                {
-                    move || script.get().map(|script| {
-                        view! { <Script>{script}</Script> }
-                    })
-                }
+                <ShowLet some=script let:script>
+                    <Script>{script}</Script>
+                </ShowLet>
             }
         })
     };

examples/hackernews/Cargo.toml

@@ -25,7 +25,7 @@ log = "0.4.22"
 serde = { version = "1.0", features = ["derive"] }
 gloo-net = { version = "0.6.0", features = ["http"] }
 reqwest = { version = "0.12.5", features = ["json"] }
-wasm-bindgen = "0.2.93"
+wasm-bindgen = "0.2.105"
 web-sys = { version = "0.3.70", features = ["AbortController", "AbortSignal"] }
 send_wrapper = "0.6.0"
 
@@ -46,12 +46,12 @@ denylist = ["actix-files", "actix-web", "leptos_actix"]
 skip_feature_sets = [["csr", "ssr"], ["csr", "hydrate"], ["ssr", "hydrate"], []]
 
 [package.metadata.leptos]
-# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name   
+# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name
 output-name = "hackernews"
 # The site root folder is where cargo-leptos generate all output. WARNING: all content of this folder will be erased on a rebuild. Use it in your server setup.
 site-root = "target/site"
 # The site-root relative folder where all compiled output (JS, WASM and CSS) is written
-# Defaults to pkg	
+# Defaults to pkg
 site-pkg-dir = "pkg"
 # [Optional] The source CSS file. If it ends with .sass or .scss then it will be compiled by dart-sass into CSS. The CSS is optimized by Lightning CSS before being written to <site-root>/<site-pkg>/app.css
 style-file = "./style.css"

examples/hackernews/src/routes/stories.rs

@@ -145,14 +145,11 @@ fn Story(story: api::Story) -> impl IntoView {
                     Either::Left(
                         view! {
                             <span>
-                                {"by "}
-                                {story
-                                    .user
-                                    .map(|user| {
-                                        view! {
-                                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                                        }
-                                    })} {format!(" {} | ", story.time_ago)}
+                                "by "
+                                <ShowLet some=story.user let:user>
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                </ShowLet>
+                                {format!(" {} | ", story.time_ago)}
                                 <A href=format!(
                                     "/stories/{}",
                                     story.id,

examples/hackernews/src/routes/story.rs

@@ -30,17 +30,13 @@ pub fn Story() -> impl IntoView {
                                 <h1>{story.title}</h1>
                             </a>
                             <span class="host">"(" {story.domain} ")"</span>
-                            {story
-                                .user
-                                .map(|user| {
-                                    view! {
-                                        <p class="meta">
-                                            {story.points} " points | by "
-                                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                                            {format!(" {}", story.time_ago)}
-                                        </p>
-                                    }
-                                })}
+                            <ShowLet some=story.user let:user>
+                                <p class="meta">
+                                    {story.points} " points | by "
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                    {format!(" {}", story.time_ago)}
+                                </p>
+                            </ShowLet>
                         </div>
                         <div class="item-view-comments">
                             <p class="item-view-comments-header">

examples/hackernews_axum/Cargo.toml

@@ -26,7 +26,7 @@ tower-http = { version = "0.5.2", features = ["fs"], optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
 http = { version = "1.1", optional = true }
 web-sys = { version = "0.3.70", features = ["AbortController", "AbortSignal"] }
-wasm-bindgen = "0.2.93"
+wasm-bindgen = "0.2.105"
 send_wrapper = { version = "0.6.0", features = ["futures"] }
 
 [features]

examples/hackernews_axum/src/routes/stories.rs

@@ -133,7 +133,9 @@ fn Story(story: api::Story) -> impl IntoView {
                     Either::Left(view! {
                         <span>
                             {"by "}
-                            {story.user.map(|user| view ! {  <A href=format!("/users/{user}")>{user.clone()}</A>})}
+                            <ShowLet some=story.user let:user>
+                                <A href=format!("/users/{user}")>{user.clone()}</A>
+                            </ShowLet>
                             {format!(" {} | ", story.time_ago)}
                             <A href=format!("/stories/{}", story.id)>
                                 {if story.comments_count.unwrap_or_default() > 0 {

examples/hackernews_axum/src/routes/story.rs

@@ -40,18 +40,20 @@ impl LazyRoute for StoryRoute {
                     <Meta name="description" content=story.title.clone()/>
                     <div class="item-view">
                         <div class="item-view-header">
-                        <a href=story.url target="_blank">
-                            <h1>{story.title}</h1>
-                        </a>
-                        <span class="host">
-                            "("{story.domain}")"
-                        </span>
-                        {story.user.map(|user| view! {  <p class="meta">
-                            {story.points}
-                            " points | by "
-                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                            {format!(" {}", story.time_ago)}
-                        </p>})}
+                            <a href=story.url target="_blank">
+                                <h1>{story.title}</h1>
+                            </a>
+                            <span class="host">
+                                "("{story.domain}")"
+                            </span>
+                            <ShowLet some=story.user let:user>
+                                <p class="meta">
+                                    {story.points}
+                                    " points | by "
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                    {format!(" {}", story.time_ago)}
+                                </p>
+                            </ShowLet>
                         </div>
                         <div class="item-view-comments">
                             <p class="item-view-comments-header">

examples/hackernews_islands_axum/src/routes/stories.rs

@@ -143,8 +143,10 @@ fn Story(story: api::Story) -> impl IntoView {
                 {if story.story_type != "job" {
                     Either::Left(view! {
                         <span>
-                            {"by "}
-                            {story.user.map(|user| view ! {  <A href=format!("/users/{user}")>{user.clone()}</A>})}
+                            "by "
+                            <ShowLet some=story.user let:user>
+                                <A href=format!("/users/{user}")>{user.clone()}</A>
+                            </ShowLet>
                             {format!(" {} | ", story.time_ago)}
                             <A href=format!("/stories/{}", story.id)>
                                 {if story.comments_count.unwrap_or_default() > 0 {

examples/hackernews_islands_axum/src/routes/story.rs

@@ -32,18 +32,20 @@ pub fn Story() -> impl IntoView {
                     <Meta name="description" content=story.title.clone()/>
                     <div class="item-view">
                         <div class="item-view-header">
-                        <a href=story.url target="_blank">
-                            <h1>{story.title}</h1>
-                        </a>
-                        <span class="host">
-                            "("{story.domain}")"
-                        </span>
-                        {story.user.map(|user| view! {  <p class="meta">
-                            {story.points}
-                            " points | by "
-                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                            {format!(" {}", story.time_ago)}
-                        </p>})}
+                            <a href=story.url target="_blank">
+                                <h1>{story.title}</h1>
+                            </a>
+                            <span class="host">
+                                "("{story.domain}")"
+                            </span>
+                            <ShowLet some=story.user let:user>
+                                <p class="meta">
+                                    {story.points}
+                                    " points | by "
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                    {format!(" {}", story.time_ago)}
+                                </p>
+                            </ShowLet>
                         </div>
                         <div class="item-view-comments">
                             <p class="item-view-comments-header">

examples/hackernews_js_fetch/src/routes/stories.rs

@@ -139,14 +139,11 @@ fn Story(story: api::Story) -> impl IntoView {
                     Either::Left(
                         view! {
                             <span>
-                                {"by "}
-                                {story
-                                    .user
-                                    .map(|user| {
-                                        view! {
-                                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                                        }
-                                    })} {format!(" {} | ", story.time_ago)}
+                                "by "
+                                <ShowLet some=story.user let:user>
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                </ShowLet>
+                                {format!(" {} | ", story.time_ago)}
                                 <A href=format!(
                                     "/stories/{}",
                                     story.id,

examples/hackernews_js_fetch/src/routes/story.rs

@@ -35,17 +35,13 @@ pub fn Story() -> impl IntoView {
                                 <h1>{story.title}</h1>
                             </a>
                             <span class="host">"("{story.domain}")"</span>
-                            {story
-                                .user
-                                .map(|user| {
-                                    view! {
-                                        <p class="meta">
-                                            {story.points} " points | by "
-                                            <A href=format!("/users/{user}")>{user.clone()}</A>
-                                            {format!(" {}", story.time_ago)}
-                                        </p>
-                                    }
-                                })}
+                            <ShowLet some=story.user let:user>
+                                <p class="meta">
+                                    {story.points} " points | by "
+                                    <A href=format!("/users/{user}")>{user.clone()}</A>
+                                    {format!(" {}", story.time_ago)}
+                                </p>
+                            </ShowLet>
                         </div>
                         <div class="item-view-comments">
                             <p class="item-view-comments-header">

examples/regression/Cargo.toml

@@ -17,7 +17,7 @@ leptos_router = { path = "../../router" }
 serde = { version = "1.0", features = ["derive"] }
 thiserror = "2.0.12"
 tokio = { version = "1.39", features = [ "rt-multi-thread", "macros", "time" ], optional = true }
-wasm-bindgen = "0.2.92"
+wasm-bindgen = "0.2.106"
 
 [features]
 hydrate = [

examples/regression/e2e/features/issue_4492.feature

@@ -0,0 +1,38 @@
+@check_issue_4492
+Feature: Regression test for issue #4492
+
+	Scenario: Scenario A should show Loading once on first load.
+		Given I see the app
+		And I can access regression test 4492
+		When I click the button a-toggle
+		Then I see a-result has the text Loading...
+		When I wait 100ms
+		Then I see a-result has the text 0
+		When I click the button a-button
+		Then I see a-result has the text 0
+		When I wait 100ms
+		Then I see a-result has the text 1
+
+	Scenario: Scenario B should never show Loading
+		Given I see the app
+		And I can access regression test 4492
+		When I click the button b-toggle
+		Then I see b-result has the text 0
+		When I click the button b-button
+		Then I see b-result has the text 0
+		When I wait 100ms
+		Then I see b-result has the text 1
+		When I click the button b-button
+		Then I see b-result has the text 1
+		When I wait 100ms
+		Then I see b-result has the text 2
+
+	Scenario: Scenario C should never show Loading
+		Given I see the app
+		And I can access regression test 4492
+		When I click the button c-toggle
+		Then I see c-result has the text 0
+		When I click the button c-button
+		Then I see c-result has the text 42
+		When I wait 100ms
+		Then I see c-result has the text 1

examples/regression/e2e/tests/fixtures/action.rs

@@ -15,3 +15,9 @@ pub async fn click_link(client: &Client, text: &str) -> Result<()> {
     link.click().await?;
     Ok(())
 }
+
+pub async fn click_button(client: &Client, id: &str) -> Result<()> {
+    let btn = find::element_by_id(&client, &id).await?;
+    btn.click().await?;
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/check.rs

@@ -7,7 +7,15 @@ pub async fn result_text_is(
     client: &Client,
     expected_text: &str,
 ) -> Result<()> {
-    let actual = find::text_at_id(client, "result").await?;
+    element_text_is(client, "result", expected_text).await
+}
+
+pub async fn element_text_is(
+    client: &Client,
+    id: &str,
+    expected_text: &str,
+) -> Result<()> {
+    let actual = find::text_at_id(client, id).await?;
     assert_eq!(&actual, expected_text);
     Ok(())
 }

examples/regression/e2e/tests/fixtures/world/action_steps.rs

@@ -20,6 +20,14 @@ async fn i_select_the_link(world: &mut AppWorld, text: String) -> Result<()> {
     Ok(())
 }
 
+#[when(regex = "^I click the button (.*)$")]
+async fn i_click_the_button(world: &mut AppWorld, id: String) -> Result<()> {
+    let client = &world.client;
+    action::click_button(client, &id).await?;
+
+    Ok(())
+}
+
 #[given(expr = "I select the following links")]
 #[when(expr = "I select the following links")]
 async fn i_select_the_following_links(
@@ -54,3 +62,10 @@ async fn i_go_back(world: &mut AppWorld) -> Result<()> {
 
     Ok(())
 }
+
+#[when(regex = r"^I wait (\d+)ms$")]
+async fn i_wait_ms(_world: &mut AppWorld, ms: u64) -> Result<()> {
+    tokio::time::sleep(std::time::Duration::from_millis(ms)).await;
+
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/world/check_steps.rs

@@ -19,6 +19,17 @@ async fn i_see_the_result_is_the_string(
     Ok(())
 }
 
+#[then(regex = r"^I see ([\w-]+) has the text (.*)$")]
+async fn i_see_element_has_text(
+    world: &mut AppWorld,
+    id: String,
+    text: String,
+) -> Result<()> {
+    let client = &world.client;
+    check::element_text_is(client, &id, &text).await?;
+    Ok(())
+}
+
 #[then(regex = r"^I see the navbar$")]
 async fn i_see_the_navbar(world: &mut AppWorld) -> Result<()> {
     let client = &world.client;

examples/regression/src/app.rs

@@ -1,7 +1,7 @@
 use crate::{
     issue_4005::Routes4005, issue_4088::Routes4088, issue_4217::Routes4217,
     issue_4285::Routes4285, issue_4296::Routes4296, issue_4324::Routes4324,
-    pr_4015::Routes4015, pr_4091::Routes4091,
+    issue_4492::Routes4492, pr_4015::Routes4015, pr_4091::Routes4091,
 };
 use leptos::prelude::*;
 use leptos_meta::{MetaTags, *};
@@ -48,6 +48,7 @@ pub fn App() -> impl IntoView {
                     <Routes4285/>
                     <Routes4296/>
                     <Routes4324/>
+                    <Routes4492/>
                 </Routes>
             </main>
         </Router>
@@ -75,6 +76,7 @@ fn HomePage() -> impl IntoView {
                 <li><a href="/4285/">"4285"</a></li>
                 <li><a href="/4296/">"4296"</a></li>
                 <li><a href="/4324/">"4324"</a></li>
+                <li><a href="/4492/">"4492"</a></li>
             </ul>
         </nav>
     }

examples/regression/src/issue_4492.rs

@@ -0,0 +1,114 @@
+use leptos::prelude::*;
+#[allow(unused_imports)]
+use leptos_router::{
+    components::Route, path, MatchNestedRoutes, NavigateOptions,
+};
+
+#[component]
+pub fn Routes4492() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <Route path=path!("4492") view=Issue4492/>
+    }
+    .into_inner()
+}
+
+#[component]
+fn Issue4492() -> impl IntoView {
+    let show_a = RwSignal::new(false);
+    let show_b = RwSignal::new(false);
+    let show_c = RwSignal::new(false);
+
+    view! {
+        <button id="a-toggle" on:click=move |_| show_a.set(!show_a.get())>"Toggle A"</button>
+        <button id="b-toggle" on:click=move |_| show_b.set(!show_b.get())>"Toggle B"</button>
+        <button id="c-toggle" on:click=move |_| show_c.set(!show_c.get())>"Toggle C"</button>
+
+        <Show when=move || show_a.get()>
+            <ScenarioA/>
+        </Show>
+        <Show when=move || show_b.get()>
+            <ScenarioB/>
+        </Show>
+        <Show when=move || show_c.get()>
+            <ScenarioC/>
+        </Show>
+    }
+}
+
+#[component]
+fn ScenarioA() -> impl IntoView {
+    // scenario A: one truly-async resource is read on click
+    let counter = RwSignal::new(0);
+    let resource = Resource::new(
+        move || counter.get(),
+        |count| async move {
+            sleep(50).await.unwrap();
+            count
+        },
+    );
+    view! {
+        <Transition fallback=|| view! { <p id="a-result">"Loading..."</p> }>
+            <p id="a-result">{resource}</p>
+        </Transition>
+        <button id="a-button" on:click=move |_| *counter.write() += 1>"+1"</button>
+    }
+}
+
+#[component]
+fn ScenarioB() -> impl IntoView {
+    // scenario B: resource immediately available first time, then after 250ms
+    let counter = RwSignal::new(0);
+    let resource = Resource::new(
+        move || counter.get(),
+        |count| async move {
+            if count == 0 {
+                count
+            } else {
+                sleep(50).await.unwrap();
+                count
+            }
+        },
+    );
+    view! {
+        <Transition fallback=|| view! { <p id="b-result">"Loading..."</p> }>
+            <p id="b-result">{resource}</p>
+        </Transition>
+        <button id="b-button" on:click=move |_| *counter.write() += 1>"+1"</button>
+    }
+}
+
+#[component]
+fn ScenarioC() -> impl IntoView {
+    // scenario C: not even a resource on the first run, just a value
+    // see https://github.com/leptos-rs/leptos/issues/3868
+    let counter = RwSignal::new(0);
+    let s_res = StoredValue::new(None::<ArcLocalResource<i32>>);
+    let resource = move || {
+        let count = counter.get();
+        if count == 0 {
+            count
+        } else {
+            let r = s_res.get_value().unwrap_or_else(|| {
+                let res = ArcLocalResource::new(move || async move {
+                    sleep(50).await.unwrap();
+                    count
+                });
+                s_res.set_value(Some(res.clone()));
+                res
+            });
+            r.get().unwrap_or(42)
+        }
+    };
+    view! {
+        <Transition fallback=|| view! { <p id="c-result">"Loading..."</p> }>
+            <p id="c-result">{resource}</p>
+        </Transition>
+        <button id="c-button" on:click=move |_| *counter.write() += 1>"+1"</button>
+    }
+}
+
+#[server]
+async fn sleep(ms: u64) -> Result<(), ServerFnError> {
+    tokio::time::sleep(std::time::Duration::from_millis(ms)).await;
+    Ok(())
+}

examples/regression/src/lib.rs

@@ -5,6 +5,7 @@ mod issue_4217;
 mod issue_4285;
 mod issue_4296;
 mod issue_4324;
+mod issue_4492;
 mod pr_4015;
 mod pr_4091;
 

examples/server_fns_axum/src/app.rs

@@ -564,17 +564,12 @@ pub fn FileUploadWithProgress() -> impl IntoView {
             <input type="submit" />
         </form>
         {move || filename.get().map(|filename| view! { <p>Uploading {filename}</p> })}
-        {move || {
-            max.get()
-                .map(|max| {
-                    view! {
-                        <progress
-                            max=max
-                            value=move || current.get().unwrap_or_default()
-                        ></progress>
-                    }
-                })
-        }}
+        <ShowLet some=max let:max>
+            <progress
+                max=max
+                value=move || current.get().unwrap_or_default()
+            ></progress>
+        </ShowLet>
     }
 }
 #[component]

examples/suspense_tests/src/instrumented.rs

@@ -663,26 +663,24 @@ impl From<Vec<FieldNavItem>> for FieldNavCtx {
 #[component]
 pub fn FieldNavPortlet() -> impl IntoView {
     let ctx = expect_context::<ReadSignal<Option<FieldNavCtx>>>();
-    move || {
-        let ctx = ctx.get();
-        ctx.map(|ctx| {
-            view! {
-                <div id="FieldNavPortlet">
-                    <span>"FieldNavPortlet:"</span>
-                    <nav>
-                        {ctx
-                            .0
-                            .map(|ctx| {
-                                ctx.into_iter()
-                                    .map(|FieldNavItem { href, text }| {
-                                        view! { <A href=href>{text}</A> }
-                                    })
-                                    .collect_view()
-                            })}
-                    </nav>
-                </div>
-            }
-        })
+
+    view! {
+        <ShowLet some=ctx let:ctx>
+            <div id="FieldNavPortlet">
+                <span>"FieldNavPortlet:"</span>
+                <nav>
+                    {ctx
+                        .0
+                        .map(|ctx| {
+                            ctx.into_iter()
+                                .map(|FieldNavItem { href, text }| {
+                                    view! { <A href=href>{text}</A> }
+                                })
+                                .collect_view()
+                        })}
+                </nav>
+            </div>
+        </ShowLet>
     }
 }
 

leptos/src/show_let.rs

@@ -160,3 +160,16 @@ where
         OptionGetter(Arc::new(move || cloned.get()))
     }
 }
+
+/// Marker type for creating an `OptionGetter` from a static value.
+/// Used so that the compiler doesn't complain about double implementations of the trait `IntoOptionGetter`.
+pub struct StaticMarker;
+
+impl<T> IntoOptionGetter<T, StaticMarker> for Option<T>
+where
+    T: Clone + Send + Sync + 'static,
+{
+    fn into_option_getter(self) -> OptionGetter<T> {
+        OptionGetter(Arc::new(move || self.clone()))
+    }
+}

leptos/src/suspense_component.rs

@@ -15,7 +15,10 @@ use reactive_graph::{
     effect::RenderEffect,
     owner::{provide_context, use_context, Owner},
     signal::ArcRwSignal,
-    traits::{Dispose, Get, Read, ReadUntracked, Track, With, WriteValue},
+    traits::{
+        Dispose, Get, Read, ReadUntracked, Track, With, WithUntracked,
+        WriteValue,
+    },
 };
 use slotmap::{DefaultKey, SlotMap};
 use std::sync::{Arc, Mutex};
@@ -119,14 +122,19 @@ where
         provide_context(SuspenseContext {
             tasks: tasks.clone(),
         });
-        let none_pending = ArcMemo::new(move |prev: Option<&bool>| {
-            tasks.track();
-            if prev.is_none() && starts_local {
-                false
-            } else {
-                tasks.with(SlotMap::is_empty)
+        let none_pending = ArcMemo::new({
+            let tasks = tasks.clone();
+            move |prev: Option<&bool>| {
+                tasks.track();
+                if prev.is_none() && starts_local {
+                    false
+                } else {
+                    tasks.with(SlotMap::is_empty)
+                }
             }
         });
+        let has_tasks =
+            Arc::new(move || !tasks.with_untracked(SlotMap::is_empty));
 
         OwnedView::new(SuspenseBoundary::<false, _, _> {
             id,
@@ -134,6 +142,7 @@ where
             fallback,
             children,
             error_boundary_parent,
+            has_tasks,
         })
     })
 }
@@ -156,6 +165,7 @@ pub(crate) struct SuspenseBoundary<const TRANSITION: bool, Fal, Chil> {
     pub fallback: Fal,
     pub children: Chil,
     pub error_boundary_parent: Option<ErrorBoundarySuspendedChildren>,
+    pub has_tasks: Arc<dyn Fn() -> bool + Send + Sync>,
 }
 
 impl<const TRANSITION: bool, Fal, Chil> Render
@@ -192,12 +202,26 @@ where
                 outer_owner.clone(),
             );
 
-            if let Some(mut state) = prev {
+            let state = if let Some(mut state) = prev {
                 this.rebuild(&mut state);
                 state
             } else {
                 this.build()
+            };
+
+            if nth_run == 1 && !(self.has_tasks)() {
+                // if this is the first run, and there are no pending resources at this point,
+                // it means that there were no actually-async resources read while rendering the children
+                // this means that we're effectively on the settled second run: none_pending
+                // won't change false => true and cause this to rerender (and therefore increment nth_run)
+                //
+                // we increment it manually here so that future resource changes won't cause the transition fallback
+                // to be displayed for the first time
+                // see https://github.com/leptos-rs/leptos/issues/3868, https://github.com/leptos-rs/leptos/issues/4492
+                nth_run += 1;
             }
+
+            state
         })
     }
 
@@ -235,6 +259,7 @@ where
             fallback,
             children,
             error_boundary_parent,
+            has_tasks,
         } = self;
         SuspenseBoundary {
             id,
@@ -242,6 +267,7 @@ where
             fallback,
             children: children.add_any_attr(attr),
             error_boundary_parent,
+            has_tasks,
         }
     }
 }

leptos/src/transition.rs

@@ -10,10 +10,11 @@ use reactive_graph::{
     effect::Effect,
     owner::{provide_context, use_context, Owner},
     signal::ArcRwSignal,
-    traits::{Get, Set, Track, With},
+    traits::{Get, Set, Track, With, WithUntracked},
     wrappers::write::SignalSetter,
 };
 use slotmap::{DefaultKey, SlotMap};
+use std::sync::Arc;
 use tachys::reactive_graph::OwnedView;
 
 /// If any [`Resource`](crate::prelude::Resource) is read in the `children` of this
@@ -104,14 +105,19 @@ where
         provide_context(SuspenseContext {
             tasks: tasks.clone(),
         });
-        let none_pending = ArcMemo::new(move |prev: Option<&bool>| {
-            tasks.track();
-            if prev.is_none() && starts_local {
-                false
-            } else {
-                tasks.with(SlotMap::is_empty)
+        let none_pending = ArcMemo::new({
+            let tasks = tasks.clone();
+            move |prev: Option<&bool>| {
+                tasks.track();
+                if prev.is_none() && starts_local {
+                    false
+                } else {
+                    tasks.with(SlotMap::is_empty)
+                }
             }
         });
+        let has_tasks =
+            Arc::new(move || !tasks.with_untracked(SlotMap::is_empty));
         if let Some(set_pending) = set_pending {
             Effect::new_isomorphic({
                 let none_pending = none_pending.clone();
@@ -127,6 +133,7 @@ where
             fallback,
             children,
             error_boundary_parent,
+            has_tasks,
         })
     })
 }

leptos_server/src/once_resource.rs

@@ -15,7 +15,7 @@ use codee::{
     Decoder, Encoder,
 };
 use core::{fmt::Debug, marker::PhantomData};
-use futures::Future;
+use futures::{Future, FutureExt};
 use or_poisoned::OrPoisoned;
 use reactive_graph::{
     computed::{
@@ -258,11 +258,17 @@ where
         if let Some(suspense_context) = use_context::<SuspenseContext>() {
             if self.value.read().or_poisoned().is_none() {
                 let handle = suspense_context.task_id();
-                let ready = SpecialNonReactiveFuture::new(self.ready());
-                reactive_graph::spawn(async move {
-                    ready.await;
-                    drop(handle);
-                });
+                let mut ready =
+                    Box::pin(SpecialNonReactiveFuture::new(self.ready()));
+                match ready.as_mut().now_or_never() {
+                    Some(_) => drop(handle),
+                    None => {
+                        reactive_graph::spawn(async move {
+                            ready.await;
+                            drop(handle);
+                        });
+                    }
+                }
                 self.suspenses.write().or_poisoned().push(suspense_context);
             }
         }

reactive_graph/src/computed/async_derived/arc_async_derived.rs

@@ -632,12 +632,29 @@ impl<T: 'static> ReadUntracked for ArcAsyncDerived<T> {
 
     fn try_read_untracked(&self) -> Option<Self::Value> {
         if let Some(suspense_context) = use_context::<SuspenseContext>() {
+            // create a handle to register it with suspense
             let handle = suspense_context.task_id();
-            let ready = SpecialNonReactiveFuture::new(self.ready());
-            crate::spawn(async move {
-                ready.await;
-                drop(handle);
-            });
+
+            // check if the task is *already* ready
+            let mut ready =
+                Box::pin(SpecialNonReactiveFuture::new(self.ready()));
+            match ready.as_mut().now_or_never() {
+                Some(_) => {
+                    // if it's already ready, drop the handle immediately
+                    // this will immediately notify the suspense context that it's complete
+                    drop(handle);
+                }
+                None => {
+                    // otherwise, spawn a task to wait for it to be ready, then drop the handle,
+                    // which will notify the suspense
+                    crate::spawn(async move {
+                        ready.await;
+                        drop(handle);
+                    });
+                }
+            }
+
+            // register the suspense context with our list of them, to be notified later if this re-runs
             self.inner
                 .write()
                 .or_poisoned()

reactive_stores/src/keyed.rs

@@ -713,3 +713,144 @@ where
             .map(|key| AtKeyed::new(self.inner.clone(), key))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{self as reactive_stores, tests::tick, AtKeyed, Store};
+    use reactive_graph::{
+        effect::Effect,
+        traits::{GetUntracked, ReadUntracked, Set, Track, Write},
+    };
+    use std::sync::{
+        atomic::{AtomicUsize, Ordering},
+        Arc,
+    };
+
+    #[derive(Debug, Store, Default)]
+    struct Todos {
+        #[store(key: usize = |todo| todo.id)]
+        todos: Vec<Todo>,
+    }
+
+    #[derive(Debug, Store, Default, Clone, PartialEq, Eq)]
+    struct Todo {
+        id: usize,
+        label: String,
+    }
+
+    impl Todo {
+        pub fn new(id: usize, label: impl ToString) -> Self {
+            Self {
+                id,
+                label: label.to_string(),
+            }
+        }
+    }
+
+    fn data() -> Todos {
+        Todos {
+            todos: vec![
+                Todo {
+                    id: 10,
+                    label: "A".to_string(),
+                },
+                Todo {
+                    id: 11,
+                    label: "B".to_string(),
+                },
+                Todo {
+                    id: 12,
+                    label: "C".to_string(),
+                },
+            ],
+        }
+    }
+    #[tokio::test]
+    async fn keyed_fields_can_be_moved() {
+        _ = any_spawner::Executor::init_tokio();
+
+        let store = Store::new(data());
+        assert_eq!(store.read_untracked().todos.len(), 3);
+
+        // create an effect to read from each keyed field
+        let a_count = Arc::new(AtomicUsize::new(0));
+        let b_count = Arc::new(AtomicUsize::new(0));
+        let c_count = Arc::new(AtomicUsize::new(0));
+
+        let a = AtKeyed::new(store.todos(), 10);
+        let b = AtKeyed::new(store.todos(), 11);
+        let c = AtKeyed::new(store.todos(), 12);
+
+        Effect::new_sync({
+            let a_count = Arc::clone(&a_count);
+            move || {
+                a.track();
+                a_count.fetch_add(1, Ordering::Relaxed);
+            }
+        });
+        Effect::new_sync({
+            let b_count = Arc::clone(&b_count);
+            move || {
+                b.track();
+                b_count.fetch_add(1, Ordering::Relaxed);
+            }
+        });
+        Effect::new_sync({
+            let c_count = Arc::clone(&c_count);
+            move || {
+                c.track();
+                c_count.fetch_add(1, Ordering::Relaxed);
+            }
+        });
+
+        tick().await;
+        assert_eq!(a_count.load(Ordering::Relaxed), 1);
+        assert_eq!(b_count.load(Ordering::Relaxed), 1);
+        assert_eq!(c_count.load(Ordering::Relaxed), 1);
+
+        // writing at a key doesn't notify siblings
+        *a.label().write() = "Foo".into();
+        tick().await;
+        assert_eq!(a_count.load(Ordering::Relaxed), 2);
+        assert_eq!(b_count.load(Ordering::Relaxed), 1);
+        assert_eq!(c_count.load(Ordering::Relaxed), 1);
+
+        // the keys can be reorganized
+        store.todos().write().swap(0, 2);
+        let after = store.todos().get_untracked();
+        assert_eq!(
+            after,
+            vec![Todo::new(12, "C"), Todo::new(11, "B"), Todo::new(10, "Foo")]
+        );
+
+        tick().await;
+        assert_eq!(a_count.load(Ordering::Relaxed), 2);
+        assert_eq!(b_count.load(Ordering::Relaxed), 1);
+        assert_eq!(c_count.load(Ordering::Relaxed), 1);
+
+        // and after we move the keys around, they still update the moved items
+        a.label().set("Bar".into());
+        let after = store.todos().get_untracked();
+        assert_eq!(
+            after,
+            vec![Todo::new(12, "C"), Todo::new(11, "B"), Todo::new(10, "Bar")]
+        );
+        tick().await;
+        assert_eq!(a_count.load(Ordering::Relaxed), 3);
+        assert_eq!(b_count.load(Ordering::Relaxed), 1);
+        assert_eq!(c_count.load(Ordering::Relaxed), 1);
+
+        // we can remove a key and add a new one
+        store.todos().write().pop();
+        store.todos().write().push(Todo::new(13, "New"));
+        let after = store.todos().get_untracked();
+        assert_eq!(
+            after,
+            vec![Todo::new(12, "C"), Todo::new(11, "B"), Todo::new(13, "New")]
+        );
+        tick().await;
+        assert_eq!(a_count.load(Ordering::Relaxed), 3);
+        assert_eq!(b_count.load(Ordering::Relaxed), 1);
+        assert_eq!(c_count.load(Ordering::Relaxed), 1);
+    }
+}