fix: get_widget did not always work for function components

We only searched through the current context, which made it work
when all parents are widget components (which do not create a new
context).
Now we search through all child contexts, which makes it work for
function components as well.

Fixes #14

reacton/core.py

@@ -742,23 +742,22 @@ def get_widget(el: Element):
     element will be returned.
     """
     rc = get_render_context()
-    if rc.context is None:
-        raise RuntimeError("get_widget() can only be used in use_effect")
-    if el.is_shared:
-        if el not in rc._shared_widgets:
-            if id(el) in rc._old_element_ids:
-                raise KeyError(f"Element {el} was found to be in a previous render, you may have used a stale element")
-            else:
-                raise KeyError(f"Element {el} not found in all known widgets for the component {rc._shared_widgets}")
-        return rc._shared_widgets[el]
-    else:
-
-        if el not in rc.context.element_to_widget:
-            if id(el) in rc._old_element_ids:
-                raise KeyError(f"Element {el} was found to be in a previous render, you may have used a stale element")
-            else:
-                raise KeyError(f"Element {el} not found in all known widgets for the component {rc.context.widgets}")
-        return rc.context.element_to_widget[el]
+    # breadth first search
+    contexts = [rc.context]
+    while contexts:
+        context = contexts.pop()
+        if context is None:
+            raise RuntimeError("get_widget() can only be used in use_effect")
+        contexts.extend(context.children.values())
+        if el.is_shared:
+            if el not in rc._shared_widgets:
+                return rc._shared_widgets[el]
+        else:
+            if el in context.element_to_widget:
+                return context.element_to_widget[el]
+    if id(el) in rc._old_element_ids:
+        raise KeyError(f"Element {el} was found to be in a previous render, you may have used a stale element")
+    raise KeyError(f"Element {el} not found in all known widgets")  # for the component {context.widgets}")
 
 
 def use_state(initial: T, key: str = None, eq: Callable[[Any, Any], bool] = None) -> Tuple[T, Callable[[Union[T, Callable[[T], T]]], None]]:

reacton/core_test.py

@@ -1380,7 +1380,7 @@ def ContainerContext(exponent=1.2):
     rc.close()
 
 
-def test_get_widget():
+def test_get_widget(Container):
 
     button1 = None
     button2 = None
@@ -1394,12 +1394,12 @@ def get_widgets():
             button2 = react.core.get_widget(button2el)
 
         use_effect(get_widgets)
-        with w.VBox() as main:
+        with Container() as main:
             button1el = w.Button(description="1")
             button2el = w.Button(description="2")
         return main
 
-    box, rc = react.render_fixed(Multiple())
+    box, rc = react.render_fixed(Multiple(), handle_error=False)
     assert box.children[0] is button1
     assert box.children[1] is button2
     rc.close()