ignore missing attributes during binding propagation

nicegui/binding.py

@@ -11,6 +11,13 @@ bindable_properties: Dict[Tuple[int, str], Any] = {}
 active_links: List[Tuple[Any, str, Any, str, Callable[[Any], Any]]] = []
 
 
+def has_attribute(obj: Union[object, Dict], name: str) -> Any:
+    if isinstance(obj, dict):
+        return name in obj
+    else:
+        return hasattr(obj, name)
+
+
 def get_attribute(obj: Union[object, Dict], name: str) -> Any:
     if isinstance(obj, dict):
         return obj[name]
@@ -31,10 +38,11 @@ async def loop() -> None:
         t = time.time()
         for link in active_links:
             (source_obj, source_name, target_obj, target_name, transform) = link
-            value = transform(get_attribute(source_obj, source_name))
-            if get_attribute(target_obj, target_name) != value:
-                set_attribute(target_obj, target_name, value)
-                propagate(target_obj, target_name, visited)
+            if has_attribute(source_obj, source_name):
+                value = transform(get_attribute(source_obj, source_name))
+                if not has_attribute(target_obj, target_name) or get_attribute(target_obj, target_name) != value:
+                    set_attribute(target_obj, target_name, value)
+                    propagate(target_obj, target_name, visited)
             del link, source_obj, target_obj
         if time.time() - t > 0.01:
             logging.warning(f'binding propagation for {len(active_links)} active links took {time.time() - t:.3f} s')
@@ -48,10 +56,11 @@ def propagate(source_obj: Any, source_name: str, visited: Optional[Set[Tuple[int
     for _, target_obj, target_name, transform in bindings.get((id(source_obj), source_name), []):
         if (id(target_obj), target_name) in visited:
             continue
-        target_value = transform(get_attribute(source_obj, source_name))
-        if get_attribute(target_obj, target_name) != target_value:
-            set_attribute(target_obj, target_name, target_value)
-            propagate(target_obj, target_name, visited)
+        if has_attribute(source_obj, source_name):
+            target_value = transform(get_attribute(source_obj, source_name))
+            if not has_attribute(target_obj, target_name) or get_attribute(target_obj, target_name) != target_value:
+                set_attribute(target_obj, target_name, target_value)
+                propagate(target_obj, target_name, visited)
 
 
 def bind_to(self_obj: Any, self_name: str, other_obj: Any, other_name: str, forward: Callable[[Any], Any]) -> None: