Fix hydration with empty spread attributes

Cargo.toml

@@ -126,6 +126,7 @@ members = [
     "packages/playwright-tests/barebones-template",
     "packages/playwright-tests/fullstack",
     "packages/playwright-tests/fullstack-mounted",
+    "packages/playwright-tests/fullstack-spread",
     "packages/playwright-tests/fullstack-routing",
     "packages/playwright-tests/suspense-carousel",
     "packages/playwright-tests/nested-suspense",

packages/core/src/diff/node.rs

@@ -819,10 +819,14 @@ impl VNode {
                 }
             };
 
+            // Write the value for each attribute in the group
             for attr in &**attribute {
                 self.write_attribute(attribute_path, attr, id, mount, dom, to);
-                dom.set_mounted_dyn_attr(mount, attribute_idx, id);
             }
+            // Set the mounted dynamic attribute once. This must be set even if no actual
+            // attributes are present so it is present for renderers like fullstack to look
+            // up the position where attributes may be inserted in the future
+            dom.set_mounted_dyn_attr(mount, attribute_idx, id);
         }
     }
 

packages/playwright-tests/fullstack-spread.spec.js

@@ -0,0 +1,13 @@
+// @ts-check
+const { test, expect } = require("@playwright/test");
+
+test("spread attributes hydrate", async ({ page }) => {
+  await page.goto("http://localhost:7979");
+
+  // Expect the page to contain the button
+  const counter = page.locator("#counter");
+  await expect(counter).toHaveText("Count: 0");
+  // Clicking on the button should increment the count
+  await counter.click();
+  await expect(counter).toHaveText("Count: 1");
+});

packages/playwright-tests/fullstack-spread/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "dioxus-playwright-fullstack-spread-test"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+dioxus = { workspace = true, features = ["fullstack"] }
+
+[features]
+default = []
+server = ["dioxus/server"]
+web = ["dioxus/web"]

packages/playwright-tests/fullstack-spread/src/main.rs

@@ -0,0 +1,40 @@
+//! Regression test for <https://github.com/DioxusLabs/dioxus/issues/4646>
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::launch(|| {
+        rsx! {
+            Comp {}
+            Comp {}
+            Button {}
+        }
+    });
+}
+
+#[component]
+fn Button() -> Element {
+    let mut count = use_signal(|| 0);
+
+    rsx! {
+        button {
+            id: "counter",
+            onclick: move |_| {
+                count += 1;
+            },
+            "Count: {count}"
+        }
+    }
+}
+
+#[component]
+fn Comp(#[props(extends = GlobalAttributes)] attributes: Vec<Attribute>) -> Element {
+    rsx! {
+        div {
+            width: 100,
+            div {
+                ..attributes,
+            }
+        }
+    }
+}

packages/playwright-tests/playwright.config.js

@@ -129,6 +129,15 @@ module.exports = defineConfig({
       reuseExistingServer: !process.env.CI,
       stdout: "pipe",
     },
+    {
+      cwd: path.join(process.cwd(), "fullstack-spread"),
+      command:
+        'cargo run --package dioxus-cli --release -- run --verbose --force-sequential --web --addr "127.0.0.1" --port 7979',
+      port: 7979,
+      timeout: 50 * 60 * 1000,
+      reuseExistingServer: !process.env.CI,
+      stdout: "pipe",
+    },
     {
       cwd: path.join(process.cwd(), "fullstack-routing"),
       command:

packages/web/src/hydration/hydrate.rs

@@ -301,9 +301,12 @@ impl WebsysDom {
                         let id = vnode
                             .mounted_dynamic_attribute(*id, dom)
                             .ok_or(VNodeNotInitialized)?;
+                        // We always need to hydrate the node even if the attributes are empty so we have
+                        // a mount for the node later. This could be spread attributes that are currently empty,
+                        // but will be filled later
+                        mounted_id = Some(id);
                         for attribute in attributes {
                             let value = &attribute.value;
-                            mounted_id = Some(id);
                             if let AttributeValue::Listener(_) = value {
                                 if attribute.name == "onmounted" {
                                     to_mount.push(id);