default-ish behavior

src/hooked_containers/mapping.py

@@ -40,7 +40,9 @@ class HookedMapping(HookedContainer[T], MutableMapping[T, MutableNesting[T]]):
     # HookedContainer methods
 
     def __getitem__(self, key: T) -> MutableNesting[T]:
-        value = self._data.get(key, {})
+        if key not in self._data:
+            self.insert(key, {})
+        value = self._data[key]
         match value:
             case HookedMapping(_data=seq):
                 return type(self)(seq, hook=self.hook, path=self.new_path(key))
@@ -50,6 +52,9 @@ class HookedMapping(HookedContainer[T], MutableMapping[T, MutableNesting[T]]):
                 return item
 
     def __setitem__(self, key: T, value: MutableNesting[T]) -> None:
+        if key not in self._data:
+            self.insert(key, value)
+            return
         self._data[key] = value
         if self.hook:
             self.hook(e.SetItemEvent(index=key, item=value, path=self.new_path(key)))