[decorators] a passthrough for debugging and visualisation

CHANGELOG.rst

@@ -3,6 +3,7 @@ Release Notes
 
 Forthcoming
 -----------
+* [decorators] a passthrough for debugging and visualisation, `#407 <https://github.com/splintered-reality/py_trees/pull/407>`_
 * ...
 
 2.2.2 (2023-01-28)

py_trees/decorators.py

@@ -893,3 +893,30 @@ def update(self) -> common.Status:
         if self.decorated.status == self.succeed_status:
             return common.Status.SUCCESS
         return common.Status.RUNNING
+
+
+class PassThrough(Decorator):
+    """
+    This decorator simply reflects the child's current status.
+
+    This behaviour is useful for debugging or visualisation purposes.
+    """
+
+    def __init__(self, name: str, child: behaviour.Behaviour):
+        """
+        Initialise with the standard decorator arguments.
+
+        Args:
+            name: the decorator name
+            child: the child to be decorated
+        """
+        super(PassThrough, self).__init__(name=name, child=child)
+
+    def update(self) -> common.Status:
+        """
+        Just reflect the child status.
+
+        Returns:
+            the behaviour's new status :class:`~py_trees.common.Status`
+        """
+        return self.decorated.status