django/tests/dispatch/tests.py

import gc
import sys
import weakref
from types import TracebackType

from django.dispatch import Signal, receiver
from django.test import SimpleTestCase
from django.test.utils import override_settings

if hasattr(sys, 'pypy_version_info'):
    def garbage_collect():
        # Collecting weakreferences can take two collections on PyPy.
        gc.collect()
        gc.collect()
else:
    def garbage_collect():
        gc.collect()


def receiver_1_arg(val, **kwargs):
    return val


class Callable:
    def __call__(self, val, **kwargs):
        return val

    def a(self, val, **kwargs):
        return val


a_signal = Signal()
b_signal = Signal()
c_signal = Signal()
d_signal = Signal(use_caching=True)


class DispatcherTests(SimpleTestCase):

    def assertTestIsClean(self, signal):
        """Assert that everything has been cleaned up automatically"""
        # Note that dead weakref cleanup happens as side effect of using
        # the signal's receivers through the signals API. So, first do a
        # call to an API method to force cleanup.
        self.assertFalse(signal.has_listeners())
        self.assertEqual(signal.receivers, [])

    @override_settings(DEBUG=True)
    def test_cannot_connect_no_kwargs(self):
        def receiver_no_kwargs(sender):
            pass

        msg = 'Signal receivers must accept keyword arguments (**kwargs).'
        with self.assertRaisesMessage(ValueError, msg):
            a_signal.connect(receiver_no_kwargs)
        self.assertTestIsClean(a_signal)

    @override_settings(DEBUG=True)
    def test_cannot_connect_non_callable(self):
        msg = 'Signal receivers must be callable.'
        with self.assertRaisesMessage(AssertionError, msg):
            a_signal.connect(object())
        self.assertTestIsClean(a_signal)

    def test_send(self):
        a_signal.connect(receiver_1_arg, sender=self)
        result = a_signal.send(sender=self, val='test')
        self.assertEqual(result, [(receiver_1_arg, 'test')])
        a_signal.disconnect(receiver_1_arg, sender=self)
        self.assertTestIsClean(a_signal)

    def test_send_no_receivers(self):
        result = a_signal.send(sender=self, val='test')
        self.assertEqual(result, [])

    def test_send_connected_no_sender(self):
        a_signal.connect(receiver_1_arg)
        result = a_signal.send(sender=self, val='test')
        self.assertEqual(result, [(receiver_1_arg, 'test')])
        a_signal.disconnect(receiver_1_arg)
        self.assertTestIsClean(a_signal)

    def test_send_different_no_sender(self):
        a_signal.connect(receiver_1_arg, sender=object)
        result = a_signal.send(sender=self, val='test')
        self.assertEqual(result, [])
        a_signal.disconnect(receiver_1_arg, sender=object)
        self.assertTestIsClean(a_signal)

    def test_garbage_collected(self):
        a = Callable()
        a_signal.connect(a.a, sender=self)
        del a
        garbage_collect()
        result = a_signal.send(sender=self, val="test")
        self.assertEqual(result, [])
        self.assertTestIsClean(a_signal)

    def test_cached_garbaged_collected(self):
        """
        Make sure signal caching sender receivers don't prevent garbage
        collection of senders.
        """
        class sender:
            pass
        wref = weakref.ref(sender)
        d_signal.connect(receiver_1_arg)
        d_signal.send(sender, val='garbage')
        del sender
        garbage_collect()
        try:
            self.assertIsNone(wref())
        finally:
            # Disconnect after reference check since it flushes the tested cache.
            d_signal.disconnect(receiver_1_arg)

    def test_multiple_registration(self):
        a = Callable()
        a_signal.connect(a)
        a_signal.connect(a)
        a_signal.connect(a)
        a_signal.connect(a)
        a_signal.connect(a)
        a_signal.connect(a)
        result = a_signal.send(sender=self, val="test")
        self.assertEqual(len(result), 1)
        self.assertEqual(len(a_signal.receivers), 1)
        del a
        del result
        garbage_collect()
        self.assertTestIsClean(a_signal)

    def test_uid_registration(self):
        def uid_based_receiver_1(**kwargs):
            pass

        def uid_based_receiver_2(**kwargs):
            pass

        a_signal.connect(uid_based_receiver_1, dispatch_uid="uid")
        a_signal.connect(uid_based_receiver_2, dispatch_uid="uid")
        self.assertEqual(len(a_signal.receivers), 1)
        a_signal.disconnect(dispatch_uid="uid")
        self.assertTestIsClean(a_signal)

    def test_send_robust_success(self):
        a_signal.connect(receiver_1_arg)
        result = a_signal.send_robust(sender=self, val='test')
        self.assertEqual(result, [(receiver_1_arg, 'test')])
        a_signal.disconnect(receiver_1_arg)
        self.assertTestIsClean(a_signal)

    def test_send_robust_no_receivers(self):
        result = a_signal.send_robust(sender=self, val='test')
        self.assertEqual(result, [])

    def test_send_robust_ignored_sender(self):
        a_signal.connect(receiver_1_arg)
        result = a_signal.send_robust(sender=self, val='test')
        self.assertEqual(result, [(receiver_1_arg, 'test')])
        a_signal.disconnect(receiver_1_arg)
        self.assertTestIsClean(a_signal)

    def test_send_robust_fail(self):
        def fails(val, **kwargs):
            raise ValueError('this')
        a_signal.connect(fails)
        try:
            with self.assertLogs('django.dispatch', 'ERROR') as cm:
                result = a_signal.send_robust(sender=self, val='test')
            err = result[0][1]
            self.assertIsInstance(err, ValueError)
            self.assertEqual(err.args, ('this',))
            self.assertIs(hasattr(err, '__traceback__'), True)
            self.assertIsInstance(err.__traceback__, TracebackType)

            log_record = cm.records[0]
            self.assertEqual(
                log_record.getMessage(),
                'Error calling '
                'DispatcherTests.test_send_robust_fail.<locals>.fails in '
                'Signal.send_robust() (this)',
            )
            self.assertIsNotNone(log_record.exc_info)
            _, exc_value, _ = log_record.exc_info
            self.assertIsInstance(exc_value, ValueError)
            self.assertEqual(str(exc_value), 'this')
        finally:
            a_signal.disconnect(fails)
        self.assertTestIsClean(a_signal)

    def test_disconnection(self):
        receiver_1 = Callable()
        receiver_2 = Callable()
        receiver_3 = Callable()
        a_signal.connect(receiver_1)
        a_signal.connect(receiver_2)
        a_signal.connect(receiver_3)
        a_signal.disconnect(receiver_1)
        del receiver_2
        garbage_collect()
        a_signal.disconnect(receiver_3)
        self.assertTestIsClean(a_signal)

    def test_values_returned_by_disconnection(self):
        receiver_1 = Callable()
        receiver_2 = Callable()
        a_signal.connect(receiver_1)
        receiver_1_disconnected = a_signal.disconnect(receiver_1)
        receiver_2_disconnected = a_signal.disconnect(receiver_2)
        self.assertTrue(receiver_1_disconnected)
        self.assertFalse(receiver_2_disconnected)
        self.assertTestIsClean(a_signal)

    def test_has_listeners(self):
        self.assertFalse(a_signal.has_listeners())
        self.assertFalse(a_signal.has_listeners(sender=object()))
        receiver_1 = Callable()
        a_signal.connect(receiver_1)
        self.assertTrue(a_signal.has_listeners())
        self.assertTrue(a_signal.has_listeners(sender=object()))
        a_signal.disconnect(receiver_1)
        self.assertFalse(a_signal.has_listeners())
        self.assertFalse(a_signal.has_listeners(sender=object()))


class ReceiverTestCase(SimpleTestCase):

    def test_receiver_single_signal(self):
        @receiver(a_signal)
        def f(val, **kwargs):
            self.state = val
        self.state = False
        a_signal.send(sender=self, val=True)
        self.assertTrue(self.state)

    def test_receiver_signal_list(self):
        @receiver([a_signal, b_signal, c_signal])
        def f(val, **kwargs):
            self.state.append(val)
        self.state = []
        a_signal.send(sender=self, val='a')
        c_signal.send(sender=self, val='c')
        b_signal.send(sender=self, val='b')
        self.assertIn('a', self.state)
        self.assertIn('b', self.state)
        self.assertIn('c', self.state)