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✏️ Editing: test_cooperator.py

# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
This module contains tests for L{twisted.internet.task.Cooperator} and
related functionality.
"""

from twisted.internet import defer, reactor, task
from twisted.trial import unittest

class FakeDelayedCall:
    """
    Fake delayed call which lets us simulate the scheduler.
    """

def __init__(self, func):
        """
        A function to run, later.
        """
        self.func = func
        self.cancelled = False

def cancel(self):
        """
        Don't run my function later.
        """
        self.cancelled = True

class FakeScheduler:
    """
    A fake scheduler for testing against.
    """

def __init__(self):
        """
        Create a fake scheduler with a list of work to do.
        """
        self.work = []

def __call__(self, thunk):
        """
        Schedule a unit of work to be done later.
        """
        unit = FakeDelayedCall(thunk)
        self.work.append(unit)
        return unit

def pump(self):
        """
        Do all of the work that is currently available to be done.
        """
        work, self.work = self.work, []
        for unit in work:
            if not unit.cancelled:
                unit.func()

class CooperatorTests(unittest.TestCase):
    RESULT = "done"

def ebIter(self, err):
        err.trap(task.SchedulerStopped)
        return self.RESULT

def cbIter(self, ign):
        self.fail()

def testStoppedRejectsNewTasks(self):
        """
        Test that Cooperators refuse new tasks when they have been stopped.
        """

def testwith(stuff):
            c = task.Cooperator()
            c.stop()
            d = c.coiterate(iter(()), stuff)
            d.addCallback(self.cbIter)
            d.addErrback(self.ebIter)
            return d.addCallback(lambda result: self.assertEqual(result, self.RESULT))

return testwith(None).addCallback(lambda ign: testwith(defer.Deferred()))

def testStopRunning(self):
        """
        Test that a running iterator will not run to completion when the
        cooperator is stopped.
        """
        c = task.Cooperator()

def myiter():
            yield from range(3)

myiter.value = -1
        d = c.coiterate(myiter())
        d.addCallback(self.cbIter)
        d.addErrback(self.ebIter)
        c.stop()

def doasserts(result):
            self.assertEqual(result, self.RESULT)
            self.assertEqual(myiter.value, -1)

d.addCallback(doasserts)
        return d

def testStopOutstanding(self):
        """
        An iterator run with L{Cooperator.coiterate} paused on a L{Deferred}
        yielded by that iterator will fire its own L{Deferred} (the one
        returned by C{coiterate}) when L{Cooperator.stop} is called.
        """
        testControlD = defer.Deferred()
        outstandingD = defer.Deferred()

def myiter():
            reactor.callLater(0, testControlD.callback, None)
            yield outstandingD
            self.fail()

c = task.Cooperator()
        d = c.coiterate(myiter())

def stopAndGo(ign):
            c.stop()
            outstandingD.callback("arglebargle")

testControlD.addCallback(stopAndGo)
        d.addCallback(self.cbIter)
        d.addErrback(self.ebIter)

return d.addCallback(lambda result: self.assertEqual(result, self.RESULT))

def testUnexpectedError(self):
        c = task.Cooperator()

def myiter():
            if False:
                yield None
            else:
                raise RuntimeError()

d = c.coiterate(myiter())
        return self.assertFailure(d, RuntimeError)

def testUnexpectedErrorActuallyLater(self):
        def myiter():
            D = defer.Deferred()
            reactor.callLater(0, D.errback, RuntimeError())
            yield D

c = task.Cooperator()
        d = c.coiterate(myiter())
        return self.assertFailure(d, RuntimeError)

def testUnexpectedErrorNotActuallyLater(self):
        def myiter():
            yield defer.fail(RuntimeError())

c = task.Cooperator()
        d = c.coiterate(myiter())
        return self.assertFailure(d, RuntimeError)

def testCooperation(self):
        L = []

def myiter(things):
            for th in things:
                L.append(th)
                yield None

groupsOfThings = ["abc", (1, 2, 3), "def", (4, 5, 6)]

c = task.Cooperator()
        tasks = []
        for stuff in groupsOfThings:
            tasks.append(c.coiterate(myiter(stuff)))

return defer.DeferredList(tasks).addCallback(
            lambda ign: self.assertEqual(tuple(L), sum(zip(*groupsOfThings), ()))
        )

def testResourceExhaustion(self):
        output = []

def myiter():
            for i in range(100):
                output.append(i)
                if i == 9:
                    _TPF.stopped = True
                yield i

class _TPF:
            stopped = False

def __call__(self):
                return self.stopped

c = task.Cooperator(terminationPredicateFactory=_TPF)
        c.coiterate(myiter()).addErrback(self.ebIter)
        c._delayedCall.cancel()
        # testing a private method because only the test case will ever care
        # about this, so we have to carefully clean up after ourselves.
        c._tick()
        c.stop()
        self.assertTrue(_TPF.stopped)
        self.assertEqual(output, list(range(10)))

def testCallbackReCoiterate(self):
        """
        If a callback to a deferred returned by coiterate calls coiterate on
        the same Cooperator, we should make sure to only do the minimal amount
        of scheduling work.  (This test was added to demonstrate a specific bug
        that was found while writing the scheduler.)
        """
        calls = []

class FakeCall:
            def __init__(self, func):
                self.func = func

def __repr__(self) -> str:
                return f"<FakeCall {self.func!r}>"

def sched(f):
            self.assertFalse(calls, repr(calls))
            calls.append(FakeCall(f))
            return calls[-1]

c = task.Cooperator(
            scheduler=sched, terminationPredicateFactory=lambda: lambda: True
        )
        d = c.coiterate(iter(()))

done = []

def anotherTask(ign):
            c.coiterate(iter(())).addBoth(done.append)

d.addCallback(anotherTask)

work = 0
        while not done:
            work += 1
            while calls:
                calls.pop(0).func()
                work += 1
            if work > 50:
                self.fail("Cooperator took too long")

def test_removingLastTaskStopsScheduledCall(self):
        """
        If the last task in a Cooperator is removed, the scheduled call for
        the next tick is cancelled, since it is no longer necessary.

This behavior is useful for tests that want to assert they have left
        no reactor state behind when they're done.
        """
        calls = [None]

def sched(f):
            calls[0] = FakeDelayedCall(f)
            return calls[0]

coop = task.Cooperator(scheduler=sched)

# Add two task; this should schedule the tick:
        task1 = coop.cooperate(iter([1, 2]))
        task2 = coop.cooperate(iter([1, 2]))
        self.assertEqual(calls[0].func, coop._tick)

# Remove first task; scheduled call should still be going:
        task1.stop()
        self.assertFalse(calls[0].cancelled)
        self.assertEqual(coop._delayedCall, calls[0])

# Remove second task; scheduled call should be cancelled:
        task2.stop()
        self.assertTrue(calls[0].cancelled)
        self.assertIsNone(coop._delayedCall)

# Add another task; scheduled call will be recreated:
        coop.cooperate(iter([1, 2]))
        self.assertFalse(calls[0].cancelled)
        self.assertEqual(coop._delayedCall, calls[0])

def test_runningWhenStarted(self):
        """
        L{Cooperator.running} reports C{True} if the L{Cooperator}
        was started on creation.
        """
        c = task.Cooperator()
        self.assertTrue(c.running)

def test_runningWhenNotStarted(self):
        """
        L{Cooperator.running} reports C{False} if the L{Cooperator}
        has not been started.
        """
        c = task.Cooperator(started=False)
        self.assertFalse(c.running)

def test_runningWhenRunning(self):
        """
        L{Cooperator.running} reports C{True} when the L{Cooperator}
        is running.
        """
        c = task.Cooperator(started=False)
        c.start()
        self.addCleanup(c.stop)
        self.assertTrue(c.running)

def test_runningWhenStopped(self):
        """
        L{Cooperator.running} reports C{False} after the L{Cooperator}
        has been stopped.
        """
        c = task.Cooperator(started=False)
        c.start()
        c.stop()
        self.assertFalse(c.running)

class UnhandledException(Exception):
    """
    An exception that should go unhandled.
    """

class AliasTests(unittest.TestCase):
    """
    Integration test to verify that the global singleton aliases do what
    they're supposed to.
    """

def test_cooperate(self):
        """
        L{twisted.internet.task.cooperate} ought to run the generator that it is
        """
        d = defer.Deferred()

def doit():
            yield 1
            yield 2
            yield 3
            d.callback("yay")

it = doit()
        theTask = task.cooperate(it)
        self.assertIn(theTask, task._theCooperator._tasks)
        return d

class RunStateTests(unittest.TestCase):
    """
    Tests to verify the behavior of L{CooperativeTask.pause},
    L{CooperativeTask.resume}, L{CooperativeTask.stop}, exhausting the
    underlying iterator, and their interactions with each other.
    """

def setUp(self):
        """
        Create a cooperator with a fake scheduler and a termination predicate
        that ensures only one unit of work will take place per tick.
        """
        self._doDeferNext = False
        self._doStopNext = False
        self._doDieNext = False
        self.work = []
        self.scheduler = FakeScheduler()
        self.cooperator = task.Cooperator(
            scheduler=self.scheduler,
            # Always stop after one iteration of work (return a function which
            # returns a function which always returns True)
            terminationPredicateFactory=lambda: lambda: True,
        )
        self.task = self.cooperator.cooperate(self.worker())
        self.cooperator.start()

def worker(self):
        """
        This is a sample generator which yields Deferreds when we are testing
        deferral and an ascending integer count otherwise.
        """
        i = 0
        while True:
            i += 1
            if self._doDeferNext:
                self._doDeferNext = False
                d = defer.Deferred()
                self.work.append(d)
                yield d
            elif self._doStopNext:
                return
            elif self._doDieNext:
                raise UnhandledException()
            else:
                self.work.append(i)
                yield i

def tearDown(self):
        """
        Drop references to interesting parts of the fixture to allow Deferred
        errors to be noticed when things start failing.
        """
        del self.task
        del self.scheduler

def deferNext(self):
        """
        Defer the next result from my worker iterator.
        """
        self._doDeferNext = True

def stopNext(self):
        """
        Make the next result from my worker iterator be completion (raising
        StopIteration).
        """
        self._doStopNext = True

def dieNext(self):
        """
        Make the next result from my worker iterator be raising an
        L{UnhandledException}.
        """

def ignoreUnhandled(failure):
            failure.trap(UnhandledException)
            return None

self._doDieNext = True

def test_pauseResume(self):
        """
        Cooperators should stop running their tasks when they're paused, and
        start again when they're resumed.
        """
        # first, sanity check
        self.scheduler.pump()
        self.assertEqual(self.work, [1])
        self.scheduler.pump()
        self.assertEqual(self.work, [1, 2])

# OK, now for real
        self.task.pause()
        self.scheduler.pump()
        self.assertEqual(self.work, [1, 2])
        self.task.resume()
        # Resuming itself shoult not do any work
        self.assertEqual(self.work, [1, 2])
        self.scheduler.pump()
        # But when the scheduler rolls around again...
        self.assertEqual(self.work, [1, 2, 3])

def test_resumeNotPaused(self):
        """
        L{CooperativeTask.resume} should raise a L{TaskNotPaused} exception if
        it was not paused; e.g. if L{CooperativeTask.pause} was not invoked
        more times than L{CooperativeTask.resume} on that object.
        """
        self.assertRaises(task.NotPaused, self.task.resume)
        self.task.pause()
        self.task.resume()
        self.assertRaises(task.NotPaused, self.task.resume)

def test_pauseTwice(self):
        """
        Pauses on tasks should behave like a stack. If a task is paused twice,
        it needs to be resumed twice.
        """
        # pause once
        self.task.pause()
        self.scheduler.pump()
        self.assertEqual(self.work, [])
        # pause twice
        self.task.pause()
        self.scheduler.pump()
        self.assertEqual(self.work, [])
        # resume once (it shouldn't)
        self.task.resume()
        self.scheduler.pump()
        self.assertEqual(self.work, [])
        # resume twice (now it should go)
        self.task.resume()
        self.scheduler.pump()
        self.assertEqual(self.work, [1])

def test_pauseWhileDeferred(self):
        """
        C{pause()}ing a task while it is waiting on an outstanding
        L{defer.Deferred} should put the task into a state where the
        outstanding L{defer.Deferred} must be called back I{and} the task is
        C{resume}d before it will continue processing.
        """
        self.deferNext()
        self.scheduler.pump()
        self.assertEqual(len(self.work), 1)
        self.assertIsInstance(self.work[0], defer.Deferred)
        self.scheduler.pump()
        self.assertEqual(len(self.work), 1)
        self.task.pause()
        self.scheduler.pump()
        self.assertEqual(len(self.work), 1)
        self.task.resume()
        self.scheduler.pump()
        self.assertEqual(len(self.work), 1)
        self.work[0].callback("STUFF!")
        self.scheduler.pump()
        self.assertEqual(len(self.work), 2)
        self.assertEqual(self.work[1], 2)

def test_whenDone(self):
        """
        L{CooperativeTask.whenDone} returns a Deferred which fires when the
        Cooperator's iterator is exhausted.  It returns a new Deferred each
        time it is called; callbacks added to other invocations will not modify
        the value that subsequent invocations will fire with.
        """

deferred1 = self.task.whenDone()
        deferred2 = self.task.whenDone()
        results1 = []
        results2 = []
        final1 = []
        final2 = []

def callbackOne(result):
            results1.append(result)
            return 1

def callbackTwo(result):
            results2.append(result)
            return 2

deferred1.addCallback(callbackOne)
        deferred2.addCallback(callbackTwo)

deferred1.addCallback(final1.append)
        deferred2.addCallback(final2.append)

# exhaust the task iterator
        # callbacks fire
        self.stopNext()
        self.scheduler.pump()

self.assertEqual(len(results1), 1)
        self.assertEqual(len(results2), 1)

self.assertIs(results1[0], self.task._iterator)
        self.assertIs(results2[0], self.task._iterator)

self.assertEqual(final1, [1])
        self.assertEqual(final2, [2])

def test_whenDoneError(self):
        """
        L{CooperativeTask.whenDone} returns a L{defer.Deferred} that will fail
        when the iterable's C{next} method raises an exception, with that
        exception.
        """
        deferred1 = self.task.whenDone()
        results = []
        deferred1.addErrback(results.append)
        self.dieNext()
        self.scheduler.pump()
        self.assertEqual(len(results), 1)
        self.assertEqual(results[0].check(UnhandledException), UnhandledException)

def test_whenDoneStop(self):
        """
        L{CooperativeTask.whenDone} returns a L{defer.Deferred} that fails with
        L{TaskStopped} when the C{stop} method is called on that
        L{CooperativeTask}.
        """
        deferred1 = self.task.whenDone()
        errors = []
        deferred1.addErrback(errors.append)
        self.task.stop()
        self.assertEqual(len(errors), 1)
        self.assertEqual(errors[0].check(task.TaskStopped), task.TaskStopped)

def test_whenDoneAlreadyDone(self):
        """
        L{CooperativeTask.whenDone} will return a L{defer.Deferred} that will
        succeed immediately if its iterator has already completed.
        """
        self.stopNext()
        self.scheduler.pump()
        results = []
        self.task.whenDone().addCallback(results.append)
        self.assertEqual(results, [self.task._iterator])

def test_stopStops(self):
        """
        C{stop()}ping a task should cause it to be removed from the run just as
        C{pause()}ing, with the distinction that C{resume()} will raise a
        L{TaskStopped} exception.
        """
        self.task.stop()
        self.scheduler.pump()
        self.assertEqual(len(self.work), 0)
        self.assertRaises(task.TaskStopped, self.task.stop)
        self.assertRaises(task.TaskStopped, self.task.pause)
        # Sanity check - it's still not scheduled, is it?
        self.scheduler.pump()
        self.assertEqual(self.work, [])

def test_pauseStopResume(self):
        """
        C{resume()}ing a paused, stopped task should be a no-op; it should not
        raise an exception, because it's paused, but neither should it actually
        do more work from the task.
        """
        self.task.pause()
        self.task.stop()
        self.task.resume()
        self.scheduler.pump()
        self.assertEqual(self.work, [])

def test_stopDeferred(self):
        """
        As a corrolary of the interaction of C{pause()} and C{unpause()},
        C{stop()}ping a task which is waiting on a L{Deferred} should cause the
        task to gracefully shut down, meaning that it should not be unpaused
        when the deferred fires.
        """
        self.deferNext()
        self.scheduler.pump()
        d = self.work.pop()
        self.assertEqual(self.task._pauseCount, 1)
        results = []
        d.addBoth(results.append)
        self.scheduler.pump()
        self.task.stop()
        self.scheduler.pump()
        d.callback(7)
        self.scheduler.pump()
        # Let's make sure that Deferred doesn't come out fried with an
        # unhandled error that will be logged.  The value is None, rather than
        # our test value, 7, because this Deferred is returned to and consumed
        # by the cooperator code.  Its callback therefore has no contract.
        self.assertEqual(results, [None])
        # But more importantly, no further work should have happened.
        self.assertEqual(self.work, [])

def test_stopExhausted(self):
        """
        C{stop()}ping a L{CooperativeTask} whose iterator has been exhausted
        should raise L{TaskDone}.
        """
        self.stopNext()
        self.scheduler.pump()
        self.assertRaises(task.TaskDone, self.task.stop)

def test_stopErrored(self):
        """
        C{stop()}ping a L{CooperativeTask} whose iterator has encountered an
        error should raise L{TaskFailed}.
        """
        self.dieNext()
        self.scheduler.pump()
        self.assertRaises(task.TaskFailed, self.task.stop)

def test_stopCooperatorReentrancy(self):
        """
        If a callback of a L{Deferred} from L{CooperativeTask.whenDone} calls
        C{Cooperator.stop} on its L{CooperativeTask._cooperator}, the
        L{Cooperator} will stop, but the L{CooperativeTask} whose callback is
        calling C{stop} should already be considered 'stopped' by the time the
        callback is running, and therefore removed from the
        L{CoooperativeTask}.
        """
        callbackPhases = []

def stopit(result):
            callbackPhases.append(result)
            self.cooperator.stop()
            # "done" here is a sanity check to make sure that we get all the
            # way through the callback; i.e. stop() shouldn't be raising an
            # exception due to the stopped-ness of our main task.
            callbackPhases.append("done")

self.task.whenDone().addCallback(stopit)
        self.stopNext()
        self.scheduler.pump()
        self.assertEqual(callbackPhases, [self.task._iterator, "done"])

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