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# -*- test-case-name: twisted.internet.test.test_defer_await -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tests for C{await} support in Deferreds.
"""
import types
from twisted.internet.defer import (
Deferred,
ensureDeferred,
fail,
maybeDeferred,
succeed,
)
from twisted.internet.task import Clock
from twisted.python.failure import Failure
from twisted.trial.unittest import TestCase
class SampleException(Exception):
"""
A specific sample exception for testing.
"""
class AwaitTests(TestCase):
"""
Tests for using Deferreds in conjunction with PEP-492.
"""
def test_awaitReturnsIterable(self):
"""
C{Deferred.__await__} returns an iterable.
"""
d = Deferred()
awaitedDeferred = d.__await__()
self.assertEqual(awaitedDeferred, iter(awaitedDeferred))
def test_deferredFromCoroutine(self):
"""
L{Deferred.fromCoroutine} will turn a coroutine into a L{Deferred}.
"""
async def run():
d = succeed("bar")
await d
res = await run2()
return res
async def run2():
d = succeed("foo")
res = await d
return res
# It's a coroutine...
r = run()
self.assertIsInstance(r, types.CoroutineType)
# Now it's a Deferred.
d = Deferred.fromCoroutine(r)
self.assertIsInstance(d, Deferred)
# The Deferred has the result we want.
res = self.successResultOf(d)
self.assertEqual(res, "foo")
def test_basic(self):
"""
L{Deferred.fromCoroutine} allows a function to C{await} on a
L{Deferred}.
"""
async def run():
d = succeed("foo")
res = await d
return res
d = Deferred.fromCoroutine(run())
res = self.successResultOf(d)
self.assertEqual(res, "foo")
def test_basicEnsureDeferred(self):
"""
L{ensureDeferred} allows a function to C{await} on a L{Deferred}.
"""
async def run():
d = succeed("foo")
res = await d
return res
d = ensureDeferred(run())
res = self.successResultOf(d)
self.assertEqual(res, "foo")
def test_exception(self):
"""
An exception in a coroutine scheduled with L{Deferred.fromCoroutine}
will cause the returned L{Deferred} to fire with a failure.
"""
async def run():
d = succeed("foo")
await d
raise ValueError("Oh no!")
d = Deferred.fromCoroutine(run())
res = self.failureResultOf(d)
self.assertEqual(type(res.value), ValueError)
self.assertEqual(res.value.args, ("Oh no!",))
def test_synchronousDeferredFailureTraceback(self):
"""
When a Deferred is awaited upon that has already failed with a Failure
that has a traceback, both the place that the synchronous traceback
comes from and the awaiting line are shown in the traceback.
"""
def raises():
raise SampleException()
it = maybeDeferred(raises)
async def doomed():
return await it
failure = self.failureResultOf(Deferred.fromCoroutine(doomed()))
self.assertIn(", in doomed\n", failure.getTraceback())
self.assertIn(", in raises\n", failure.getTraceback())
def test_asyncDeferredFailureTraceback(self):
"""
When a Deferred is awaited upon that later fails with a Failure that
has a traceback, both the place that the synchronous traceback comes
from and the awaiting line are shown in the traceback.
"""
def returnsFailure():
try:
raise SampleException()
except SampleException:
return Failure()
it = Deferred()
async def doomed():
return await it
started = Deferred.fromCoroutine(doomed())
self.assertNoResult(started)
it.errback(returnsFailure())
failure = self.failureResultOf(started)
self.assertIn(", in doomed\n", failure.getTraceback())
self.assertIn(", in returnsFailure\n", failure.getTraceback())
def test_twoDeep(self):
"""
A coroutine scheduled with L{Deferred.fromCoroutine} that awaits a
L{Deferred} suspends its execution until the inner L{Deferred} fires.
"""
reactor = Clock()
sections = []
async def runone():
sections.append(2)
d = Deferred()
reactor.callLater(1, d.callback, 2)
await d
sections.append(3)
return "Yay!"
async def run():
sections.append(1)
result = await runone()
sections.append(4)
d = Deferred()
reactor.callLater(1, d.callback, 1)
await d
sections.append(5)
return result
d = Deferred.fromCoroutine(run())
reactor.advance(0.9)
self.assertEqual(sections, [1, 2])
reactor.advance(0.1)
self.assertEqual(sections, [1, 2, 3, 4])
reactor.advance(0.9)
self.assertEqual(sections, [1, 2, 3, 4])
reactor.advance(0.1)
self.assertEqual(sections, [1, 2, 3, 4, 5])
res = self.successResultOf(d)
self.assertEqual(res, "Yay!")
def test_reraise(self):
"""
Awaiting an already failed Deferred will raise the exception.
"""
async def test():
try:
await fail(ValueError("Boom"))
except ValueError as e:
self.assertEqual(e.args, ("Boom",))
return 1
return 0
res = self.successResultOf(Deferred.fromCoroutine(test()))
self.assertEqual(res, 1)
def test_chained(self):
"""
Awaiting a paused & chained Deferred will give the result when it has
one.
"""
reactor = Clock()
async def test():
d = Deferred()
d2 = Deferred()
d.addCallback(lambda ignored: d2)
d.callback(None)
reactor.callLater(0, d2.callback, "bye")
return await d
d = Deferred.fromCoroutine(test())
reactor.advance(0.1)
res = self.successResultOf(d)
self.assertEqual(res, "bye")
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