[decorators] finally-style decorators and idioms

.vscode/settings.json

@@ -12,10 +12,15 @@
  "behaviours",
  "bierner",
  "bungcip",
+ "epilog",
+ "graphviz",
+ "literalinclude",
+ "noodly",
  "omnilib",
  "py_trees",
  "pydot",
  "pypi",
+ "seealso",
  "ufmt",
  "usort"
  ]

CHANGELOG.rst

@@ -3,7 +3,7 @@ Release Notes
 
 Forthcoming
 -----------
-* ...
+* [decorators] finally-style decorators and idioms, `#427 <https://github.com/splintered-reality/py_trees/pull/427>`_
 
 2.2.3 (2023-02-08)
 ------------------

docs/demos.rst

@@ -147,6 +147,22 @@ py-trees-demo-eternal-guard
  :linenos:
  :caption: py_trees/demos/eternal_guard.py
 
+.. _py-trees-demo-eventually-program:
+
+py-trees-demo-eventually
+------------------------
+
+.. automodule:: py_trees.demos.eventually
+ :members:
+ :special-members:
+ :show-inheritance:
+ :synopsis: demo the finally-like decorator
+
+.. literalinclude:: ../py_trees/demos/eventually.py
+ :language: python
+ :linenos:
+ :caption: py_trees/demos/eventually.py
+
 .. _py-trees-demo-logging-program:
 
 py-trees-demo-logging

docs/dot/demo-eventually.dot

@@ -0,0 +1,17 @@
+digraph pastafarianism {
+ordering=out;
+graph [fontname="times-roman"];
+node [fontname="times-roman"];
+edge [fontname="times-roman"];
+root [fillcolor=orange, fontcolor=black, fontsize=9, label="Ⓜ root", shape=box, style=filled];
+SetFlagFalse [fillcolor=gray, fontcolor=black, fontsize=9, label=SetFlagFalse, shape=ellipse, style=filled];
+root -> SetFlagFalse;
+Parallel [fillcolor=gold, fontcolor=black, fontsize=9, label="Parallel\nSuccessOnOne", shape=parallelogram, style=filled];
+root -> Parallel;
+Counter [fillcolor=gray, fontcolor=black, fontsize=9, label=Counter, shape=ellipse, style=filled];
+Parallel -> Counter;
+Eventually [fillcolor=ghostwhite, fontcolor=black, fontsize=9, label=Eventually, shape=ellipse, style=filled];
+Parallel -> Eventually;
+SetFlagTrue [fillcolor=gray, fontcolor=black, fontsize=9, label=SetFlagTrue, shape=ellipse, style=filled];
+Eventually -> SetFlagTrue;
+}

docs/dot/demo-finally-single-tick.dot

@@ -0,0 +1,17 @@
+digraph pastafarianism {
+ordering=out;
+graph [fontname="times-roman"];
+node [fontname="times-roman"];
+edge [fontname="times-roman"];
+root [fillcolor=orange, fontcolor=black, fontsize=9, label="Ⓜ root", shape=box, style=filled];
+SetFlagFalse [fillcolor=gray, fontcolor=black, fontsize=9, label=SetFlagFalse, shape=ellipse, style=filled];
+root -> SetFlagFalse;
+Parallel [fillcolor=gold, fontcolor=black, fontsize=9, label="Parallel\nSuccessOnOne", shape=parallelogram, style=filled];
+root -> Parallel;
+Counter [fillcolor=gray, fontcolor=black, fontsize=9, label=Counter, shape=ellipse, style=filled];
+Parallel -> Counter;
+Finally [fillcolor=ghostwhite, fontcolor=black, fontsize=9, label=Finally, shape=ellipse, style=filled];
+Parallel -> Finally;
+SetFlagTrue [fillcolor=gray, fontcolor=black, fontsize=9, label=SetFlagTrue, shape=ellipse, style=filled];
+Finally -> SetFlagTrue;
+}

docs/dot/eventually.dot

@@ -0,0 +1,17 @@
+digraph pastafarianism {
+ordering=out;
+graph [fontname="times-roman"];
+node [fontname="times-roman"];
+edge [fontname="times-roman"];
+Parallel [fillcolor=gold, fontcolor=black, fontsize=9, label="Parallel\nSuccessOnOne", shape=parallelogram, style=filled];
+Worker [fillcolor=orange, fontcolor=black, fontsize=9, label="Ⓜ Worker", shape=box, style=filled];
+Parallel -> Worker;
+Glory [fillcolor=gray, fontcolor=black, fontsize=9, label=Glory, shape=ellipse, style=filled];
+Worker -> Glory;
+Infamy [fillcolor=gray, fontcolor=black, fontsize=9, label=Infamy, shape=ellipse, style=filled];
+Worker -> Infamy;
+Eventually [fillcolor=ghostwhite, fontcolor=black, fontsize=9, label=Eventually, shape=ellipse, style=filled];
+Parallel -> Eventually;
+Colander [fillcolor=gray, fontcolor=black, fontsize=9, label=Colander, shape=ellipse, style=filled];
+Eventually -> Colander;
+}

docs/examples/eventually.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import py_trees
+
+if __name__ == "__main__":
+ root = py_trees
+ task_one = py_trees.behaviours.StatusQueue(
+ name="Glory",
+ queue=[
+ py_trees.common.Status.RUNNING,
+ ],
+ eventually=py_trees.common.Status.SUCCESS,
+ )
+ task_two = py_trees.behaviours.Success(name="Infamy")
+ worker = py_trees.composites.Sequence(
+ name="Worker", memory=True, children=[task_one, task_two]
+ )
+ root = py_trees.idioms.eventually(
+ name="Parallel",
+ worker=worker,
+ eventually=py_trees.behaviours.Success("Colander"),
+ )
+ py_trees.display.render_dot_tree(
+ root, py_trees.common.string_to_visibility_level("all")
+ )

py_trees/behaviour.py

@@ -344,7 +344,7 @@ def iterate(self, direct_descendants: bool = False) -> typing.Iterator[Behaviour
  yield child
  yield self
 
- # TODO: better type refinement of 'viso=itor'
+ # TODO: better type refinement of 'visitor'
  def visit(self, visitor: typing.Any) -> None:
  """
  Introspect on this behaviour with a visitor.

py_trees/behaviours.py

@@ -280,6 +280,7 @@ def update(self) -> common.Status:
  :data:`~py_trees.common.Status.RUNNING` while not expired, the given completion status otherwise
  """
  self.counter += 1
+ self.feedback_message = f"count: {self.counter}"
  if self.counter <= self.duration:
  return common.Status.RUNNING
  else:

py_trees/decorators.py

@@ -38,6 +38,7 @@
 * :class:`py_trees.decorators.EternalGuard`
 * :class:`py_trees.decorators.Inverter`
 * :class:`py_trees.decorators.OneShot`
+* :class:`py_trees.decorators.OnTerminate`
 * :class:`py_trees.decorators.Repeat`
 * :class:`py_trees.decorators.Retry`
 * :class:`py_trees.decorators.StatusToBlackboard`
@@ -920,3 +921,79 @@ def update(self) -> common.Status:
  the behaviour's new status :class:`~py_trees.common.Status`
  """
  return self.decorated.status
+
+
+class OnTerminate(Decorator):
+ """
+ Trigger the child for a single tick on :meth:`terminate`.
+
+ Always return :data:`~py_trees.common.Status.RUNNING` and on
+ on :meth:`terminate`, call the child's
+ :meth:`~py_trees.behaviour.Behaviour.update` method, once.
+
+ This is useful to cleanup, restore a context switch or to
+ implement a finally-like behaviour.
+
+ .. seealso:: :meth:`py_trees.idioms.eventually`
+
+ NB: If you need to persist the execution of the 'finally'-like block for more
+ than a single tick, you'll need to build that explicitly into your tree. There
+ are various ways of doing so (with and without the blackboard). One pattern
+ that works:
+
+ .. code-block::
+
+ [o] Selector
+ {-} Sequence
+ --> Work
+ --> Finally (Triggers on Success)
+ {-} Sequence
+ --> Finally (Triggers on Failure)
+ --> Failure
+ """
+
+ 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(OnTerminate, self).__init__(name=name, child=child)
+
+ def tick(self) -> typing.Iterator[behaviour.Behaviour]:
+ """
+ Bypass the child when ticking.
+
+ Yields:
+ a reference to itself
+ """
+ self.logger.debug(f"{self.__class__.__name__}.tick()")
+ self.status = self.update()
+ yield self
+
+ def update(self):
+ """
+ Return with :data:`~py_trees.common.Status.RUNNING`.
+
+ Returns:
+ the behaviour's new status :class:`~py_trees.common.Status`
+ """
+ return common.Status.RUNNING
+
+ def terminate(self, new_status: common.Status) -> None:
+ """Tick the child behaviour once."""
+ self.logger.debug(
+ "{}.terminate({})".format(
+ self.__class__.__name__,
+ "{}->{}".format(self.status, new_status)
+ if self.status != new_status
+ else f"{new_status}",
+ )
+ )
+ if new_status == common.Status.INVALID:
+ self.decorated.tick_once()
+ # Do not need to stop the child here - this method
+ # is only called by Decorator.stop() which will handle
+ # that responsibility immediately after this method returns.

py_trees/demos/__init__.py

@@ -21,6 +21,7 @@
 from . import display_modes # usort:skip # noqa: F401
 from . import dot_graphs # usort:skip # noqa: F401
 from . import either_or # usort:skip # noqa: F401
+from . import eventually # usort:skip # noqa: F401
 from . import lifecycle # usort:skip # noqa: F401
 from . import selector # usort:skip # noqa: F401
 from . import sequence # usort:skip # noqa: F401