Make edit.cut a no-op when only a text caret is set (#920)

Found while testing crates/engine/src/cmd/edit.rs:cut (about line 337) and delete (about line 523)

Co-authored-by: Claude Haiku 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/edit.rs

@@ -175,7 +175,11 @@ fn copied_html(s: &Session) -> String {
 fn cut(s: &mut Session, p: &Value) -> Result<Value> {
     let caret = copying_caret(s);
     let t = copy_inner(s, p)?;
-    let html = if caret { String::new() } else { copied_html(s) };
+    if caret {
+        // Nothing is selected, so there is nothing to cut; `delete` would remove the next character.
+        return Ok(json!({"text": t, "html": ""}));
+    }
+    let html = copied_html(s);
     delete(s, p)?;
     Ok(json!({"text": t, "html": html}))
 }

crates/engine/src/tests.rs

@@ -94,6 +94,26 @@ fn text_editing_flow() {
     assert_eq!(s.doc().unwrap().selection.shapes.len(), 1);
 }
 
+/// Cut with only a caret copies nothing, so it must not delete the character after the caret.
+#[test]
+fn cut_with_only_a_caret_changes_nothing() {
+    let mut s = session();
+    let r = s.execute("insert.textBox", &json!({"text": "Hello"})).unwrap();
+    let id = r["id"].as_u64().unwrap();
+    s.execute("text.edit", &json!({"id": id})).unwrap();
+    s.execute("text.move", &json!({"to": "start"})).unwrap();
+    let out = s.execute("edit.cut", &json!({})).unwrap();
+    assert_eq!(out["text"], "");
+    let t = s.execute("text.get", &json!({"id": id})).unwrap();
+    assert_eq!(t["text"], "Hello", "cut with only a caret changed the text");
+    // A real selection is still cut.
+    s.execute("text.move", &json!({"to": "end", "extend": true})).unwrap();
+    let out = s.execute("edit.cut", &json!({})).unwrap();
+    assert_eq!(out["text"], "Hello");
+    let t = s.execute("text.get", &json!({"id": id})).unwrap();
+    assert_eq!(t["text"], "");
+}
+
 #[test]
 fn editing_text_refits_a_saved_shrink() {
     use deckcraft_model::text::AutoFit;