Source code for traits_futures.asyncio.event_loop_helper
# (C) Copyright 2018-2021 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
"""
Test support, providing the ability to run the event loop from tests.
"""
from traits_futures.i_event_loop_helper import IEventLoopHelper
[docs]@IEventLoopHelper.register
class EventLoopHelper:
"""
Support for running the asyncio event loop in unit tests.
Parameters
----------
event_loop : asyncio.AbstractEventLoop
The asyncio event loop that this object wraps.
"""
def __init__(self, event_loop):
self._event_loop = event_loop
[docs] def dispose(self):
"""
Dispose of any resources used by this object.
"""
self._event_loop = None
[docs] def setattr_soon(self, obj, name, value):
"""
Arrange for an attribute to be set once the event loop is running.
In typical usage, *obj* will be a ``HasTraits`` instance and
*name* will be the name of a trait on *obj*.
This method is not thread-safe. It's designed to be called
from the main thread.
Parameters
----------
obj : object
Object to set the given attribute on.
name : str
Name of the attribute to set; typically this is
a traited attribute.
value : object
Value to set the attribute to.
"""
self._event_loop.call_soon(setattr, obj, name, value)
[docs] def run_until(self, object, trait, condition, timeout):
"""
Run event loop until a given condition occurs, or timeout.
The condition is re-evaluated, with the object as argument, every time
the trait changes.
Parameters
----------
object : traits.has_traits.HasTraits
Object whose trait we monitor.
trait : str
Name of the trait to monitor for changes.
condition
Single-argument callable, returning a boolean. This will be
called with *object* as the only input.
timeout : float
Number of seconds to allow before timing out with an exception.
Raises
------
RuntimeError
If timeout is reached, regardless of whether the condition is
true or not at that point.
"""
timed_out = []
event_loop = self._event_loop
def stop_on_timeout():
timed_out.append(True)
event_loop.stop()
def stop_if_condition(event):
if condition(object):
event_loop.stop()
object.observe(stop_if_condition, trait)
try:
# The condition may have become True before we
# started listening to changes. So start with a check.
if not condition(object):
timer_handle = event_loop.call_later(timeout, stop_on_timeout)
try:
event_loop.run_forever()
finally:
timer_handle.cancel()
finally:
object.observe(stop_if_condition, trait, remove=True)
if timed_out:
raise RuntimeError(
"run_until timed out after {} seconds. "
"At timeout, condition was {}.".format(
timeout, condition(object)
)
)
