Merge static and dynamic styles (#3950)

* Merge static and dynamic styles

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/playwright-tests/web.spec.js

@@ -156,6 +156,16 @@ test("document elements", async ({ page }) => {
   await expect(main).toHaveCSS("font-family", "Roboto");
 });
 
+test("merge styles", async ({ page }) => {
+  await page.goto("http://localhost:9999");
+  // wait until the div is mounted
+  const div = page.locator("div#merge-styles-div");
+  await div.waitFor({ state: "attached" });
+  await expect(div).toHaveCSS("background-color", "rgb(255, 0, 0)");
+  await expect(div).toHaveCSS("width", "100px");
+  await expect(div).toHaveCSS("height", "100px");
+});
+
 test("select multiple", async ({ page }) => {
   await page.goto("http://localhost:9999");
   // wait until the select element is mounted

packages/playwright-tests/web/src/main.rs

@@ -63,6 +63,7 @@ fn app() -> Element {
         OnMounted {}
         WebSysClosure {}
         DocumentElements {}
+        MergeStyles {}
         SelectMultiple {}
     }
 }
@@ -156,6 +157,20 @@ fn DocumentElements() -> Element {
     }
 }
 
+// Regression test for https://github.com/DioxusLabs/dioxus/issues/3887
+#[component]
+fn MergeStyles() -> Element {
+    let px = 100;
+
+    rsx! {
+        div {
+            id: "merge-styles-div",
+            style: "width: {px}px; height: {px}px",
+            background_color: "red",
+        }
+    }
+}
+
 // Select elements have odd default behavior when you set the multiple attribute after mounting the element
 // Regression test for https://github.com/DioxusLabs/dioxus/issues/3185
 #[component]