Add on_pop method (#110)

Author: timonegk

dynamic_stack_decider/dynamic_stack_decider/abstract_stack_element.py

@@ -52,6 +52,14 @@ def pop(self):
         """
         self._dsd.pop()
 
+    def on_pop(self):  # noqa
+        """
+        This method is called when the element is popped from the stack.
+        It can be used to clean up resources, cancel actions or similar tasks.
+        Overload this method if you need to do something when the element is popped.
+        """
+        pass
+
     @abstractmethod
     def perform(self, reevaluate=False):
         """

dynamic_stack_decider/dynamic_stack_decider/dsd.py

@@ -259,7 +259,8 @@ def update(self, reevaluate: bool = True):
                         elif result != self.stack[self.stack_exec_index + 1][0].activation_reason:
                             # In this case, however, the activation reason actually did change. Therefore, we have to
                             # discard everything in the stack above the current decision and push the new result.
-                            self.stack = self.stack[0 : self.stack_exec_index + 1]
+                            for _ in range(self.stack_exec_index + 1, len(self.stack)):
+                                self.stack.pop()[1].on_pop()
                             self.stack_reevaluate = False
                             self.push(tree_element.get_child(result))
 
@@ -309,8 +310,9 @@ def pop(self):
             if self.stack_reevaluate:
                 # we are currently reevaluating. we shorten the stack here
                 if self.stack_exec_index > 0:
-                    # only shorten stack if it still has one element
-                    self.stack = self.stack[0 : self.stack_exec_index]
+                    ## only shorten stack if it still has one element
+                    for _ in range(self.stack_exec_index, len(self.stack)):
+                        self.stack.pop()[1].on_pop()
                 # stop reevaluating
                 self.stack_reevaluate = False
             else:
@@ -321,10 +323,10 @@ def pop(self):
                         # only a single element of the sequence
                         # We also do not want to reset do_not_reevaluate because an action in the sequence
                         # may control the stack beyond its own lifetime but in the sequence element's lifetime
-                        self.stack[-1][1].pop_one()
+                        self.stack[-1][1].pop_one().on_pop()
                         return
                 # Remove the last element of the stack
-                self.stack.pop()
+                self.stack.pop()[1].on_pop()
 
             # We will reevaluate even when the popped element set do_not_reevaluate
             # because no module should control the stack beyond its lifetime

dynamic_stack_decider/dynamic_stack_decider/sequence_element.py

@@ -63,11 +63,22 @@ def pop_one(self):
         assert not self.in_last_element(), (
             "It is not possible to pop a single element when" "the last element of the sequence is active"
         )
+        # Save the current action to return it
+        popped_action = self.current_action
         # Increment the index to the next action and initialize it
         self.current_action_index += 1
-        # We initilize the current action here to avoid the problem described in
+        # We initialize the current action here to avoid the problem described in
         # https://github.com/bit-bots/dynamic_stack_decider/issues/107
         self.current_action = self._init_function(self.actions[self.current_action_index])
+        # Return the popped action
+        return popped_action
+
+    def on_pop(self):
+        """
+        This method is called when the sequence is popped from the stack.
+        This means that the last element of the sequence was also popped, so
+        """
+        self.current_action.on_pop()
 
     def in_last_element(self):
         """Returns if the current element is the last element of the sequence"""