Fix parent attribute lookup to be default

Fixes #12526

lib/ansible/playbook/base.py

@@ -105,7 +105,10 @@ class Base:
         if hasattr(self, method):
             return getattr(self, method)()
 
-        return self._attributes[prop_name]
+        value = self._attributes[prop_name]
+        if value is None and hasattr(self, '_get_parent_attribute'):
+            value = self._get_parent_attribute(prop_name)
+        return value
 
     @staticmethod
     def _generic_s(prop_name, self, value):

lib/ansible/playbook/block.py

@@ -271,7 +271,10 @@ class Block(Base, Become, Conditional, Taggable):
         Generic logic to get the attribute or parent attribute for a block value.
         '''
 
+        value = None
+        try:
             value = self._attributes[attr]
+
             if self._parent_block and (value is None or extend):
                 parent_value = getattr(self._parent_block, attr)
                 if extend:
@@ -310,6 +313,8 @@ class Block(Base, Become, Conditional, Taggable):
                     value = self._extend_value(value, parent_value)
                 else:
                     value = parent_value
+        except KeyError:
+            pass
 
         return value
 

lib/ansible/playbook/task.py

@@ -363,7 +363,10 @@ class Task(Base, Conditional, Taggable, Become):
         '''
         Generic logic to get the attribute or parent attribute for a task value.
         '''
+        value = None
+        try:
             value = self._attributes[attr]
+
             if self._block and (value is None or extend):
                 parent_value = getattr(self._block, attr)
                 if extend:
@@ -376,6 +379,9 @@ class Task(Base, Conditional, Taggable, Become):
                     value = self._extend_value(value, parent_value)
                 else:
                     value = parent_value
+        except KeyError:
+            pass
+
         return value
 
     def _get_attr_environment(self):