Fix diffing Option<String> (#2746)

packages/core/tests/diff_dynamic_node.rs

@@ -0,0 +1,47 @@
+use dioxus::dioxus_core::{ElementId, Mutation::*};
+use dioxus::prelude::*;
+use pretty_assertions::assert_eq;
+
+#[test]
+fn toggle_option_text() {
+    let mut dom = VirtualDom::new(|| {
+        let gen = generation();
+        let text = if gen % 2 != 0 { Some("hello") } else { None };
+
+        rsx! {
+            div {
+                {text}
+            }
+        }
+    });
+
+    // load the div and then assign the None as a placeholder
+    assert_eq!(
+        dom.rebuild_to_vec().sanitize().edits,
+        [
+            LoadTemplate { name: "template", index: 0, id: ElementId(1,) },
+            AssignId { path: &[0], id: ElementId(2,) },
+            AppendChildren { id: ElementId(0), m: 1 },
+        ]
+    );
+
+    // Rendering again should replace the placeholder with an text node
+    dom.mark_dirty(ScopeId::APP);
+    assert_eq!(
+        dom.render_immediate_to_vec().sanitize().edits,
+        [
+            CreateTextNode { value: "hello".to_string(), id: ElementId(3,) },
+            ReplaceWith { id: ElementId(2,), m: 1 },
+        ]
+    );
+
+    // Rendering again should replace the placeholder with an text node
+    dom.mark_dirty(ScopeId::APP);
+    assert_eq!(
+        dom.render_immediate_to_vec().sanitize().edits,
+        [
+            CreatePlaceholder { id: ElementId(2,) },
+            ReplaceWith { id: ElementId(3,), m: 1 },
+        ]
+    );
+}