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Diffstat (limited to 'testing/marionette/client/marionette_driver/wait.py')
| -rw-r--r-- | testing/marionette/client/marionette_driver/wait.py | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/testing/marionette/client/marionette_driver/wait.py b/testing/marionette/client/marionette_driver/wait.py new file mode 100644 index 000000000..c89465ce4 --- /dev/null +++ b/testing/marionette/client/marionette_driver/wait.py @@ -0,0 +1,167 @@ +# This Source Code Form is subject to the terms of the Mozilla Public +# License, v. 2.0. If a copy of the MPL was not distributed with this +# file, You can obtain one at http://mozilla.org/MPL/2.0/. + +import collections +import errors +import sys +import time + +DEFAULT_TIMEOUT = 5 +DEFAULT_INTERVAL = 0.1 + + +class Wait(object): + + """An explicit conditional utility class for waiting until a condition + evaluates to true or not null. + + This will repeatedly evaluate a condition in anticipation for a + truthy return value, or its timeout to expire, or its waiting + predicate to become true. + + A `Wait` instance defines the maximum amount of time to wait for a + condition, as well as the frequency with which to check the + condition. Furthermore, the user may configure the wait to ignore + specific types of exceptions whilst waiting, such as + `errors.NoSuchElementException` when searching for an element on + the page. + + """ + + def __init__(self, marionette, timeout=DEFAULT_TIMEOUT, + interval=DEFAULT_INTERVAL, ignored_exceptions=None, + clock=None): + """Configure the Wait instance to have a custom timeout, interval, and + list of ignored exceptions. Optionally a different time + implementation than the one provided by the standard library + (time) can also be provided. + + Sample usage:: + + # Wait 30 seconds for window to open, checking for its presence once + # every 5 seconds. + wait = Wait(marionette, timeout=30, interval=5, + ignored_exceptions=errors.NoSuchWindowException) + window = wait.until(lambda m: m.switch_to_window(42)) + + :param marionette: The input value to be provided to + conditions, usually a Marionette instance. + + :param timeout: How long to wait for the evaluated condition + to become true. The default timeout is + `wait.DEFAULT_TIMEOUT`. + + :param interval: How often the condition should be evaluated. + In reality the interval may be greater as the cost of + evaluating the condition function. If that is not the case the + interval for the next condition function call is shortend to keep + the original interval sequence as best as possible. + The default polling interval is `wait.DEFAULT_INTERVAL`. + + :param ignored_exceptions: Ignore specific types of exceptions + whilst waiting for the condition. Any exceptions not + whitelisted will be allowed to propagate, terminating the + wait. + + :param clock: Allows overriding the use of the runtime's + default time library. See `wait.SystemClock` for + implementation details. + + """ + + self.marionette = marionette + self.timeout = timeout + self.clock = clock or SystemClock() + self.end = self.clock.now + self.timeout + self.interval = interval + + exceptions = [] + if ignored_exceptions is not None: + if isinstance(ignored_exceptions, collections.Iterable): + exceptions.extend(iter(ignored_exceptions)) + else: + exceptions.append(ignored_exceptions) + self.exceptions = tuple(set(exceptions)) + + def until(self, condition, is_true=None, message=""): + """Repeatedly runs condition until its return value evaluates to true, + or its timeout expires or the predicate evaluates to true. + + This will poll at the given interval until the given timeout + is reached, or the predicate or conditions returns true. A + condition that returns null or does not evaluate to true will + fully elapse its timeout before raising an + `errors.TimeoutException`. + + If an exception is raised in the condition function and it's + not ignored, this function will raise immediately. If the + exception is ignored, it will continue polling for the + condition until it returns successfully or a + `TimeoutException` is raised. + + :param condition: A callable function whose return value will + be returned by this function if it evaluates to true. + + :param is_true: An optional predicate that will terminate and + return when it evaluates to False. It should be a + function that will be passed clock and an end time. The + default predicate will terminate a wait when the clock + elapses the timeout. + + :param message: An optional message to include in the + exception's message if this function times out. + + """ + + rv = None + last_exc = None + until = is_true or until_pred + start = self.clock.now + + while not until(self.clock, self.end): + try: + next = self.clock.now + self.interval + rv = condition(self.marionette) + except (KeyboardInterrupt, SystemExit): + raise + except self.exceptions: + last_exc = sys.exc_info() + + # Re-adjust the interval depending on how long the callback + # took to evaluate the condition + interval_new = max(next - self.clock.now, 0) + + if not rv: + self.clock.sleep(interval_new) + continue + + if rv is not None: + return rv + + self.clock.sleep(interval_new) + + if message: + message = " with message: {}".format(message) + + raise errors.TimeoutException( + "Timed out after {0} seconds{1}".format(round((self.clock.now - start), 1), + message if message else ""), + cause=last_exc) + + +def until_pred(clock, end): + return clock.now >= end + + +class SystemClock(object): + + def __init__(self): + self._time = time + + def sleep(self, duration): + self._time.sleep(duration) + + @property + def now(self): + return self._time.time() |