tests/test_sync.py

# -*- coding: utf-8 -*-
from collections import OrderedDict

from mock import Mock
from pytest import raises

from pyee import EventEmitter


class PyeeTestException(Exception):
    pass


def test_emit_sync():
    """Basic synchronous emission works"""

    call_me = Mock()
    ee = EventEmitter()

    @ee.on("event")
    def event_handler(data, **kwargs):
        call_me()
        assert data == "emitter is emitted!"

    assert ee.event_names() == {"event"}

    # Making sure data is passed propers
    ee.emit("event", "emitter is emitted!", error=False)

    call_me.assert_called_once()


def test_emit_error():
    """Errors raise with no event handler, otherwise emit on handler"""

    call_me = Mock()
    ee = EventEmitter()

    test_exception = PyeeTestException("lololol")

    with raises(PyeeTestException):
        ee.emit("error", test_exception)

    @ee.on("error")
    def on_error(exc):
        call_me()

    assert ee.event_names() == {"error"}

    # No longer raises and error instead return True indicating handled
    assert ee.emit("error", test_exception) is True
    call_me.assert_called_once()


def test_emit_return():
    """Emit returns True when handlers are registered on an event, and false
    otherwise.
    """

    call_me = Mock()
    ee = EventEmitter()

    assert ee.event_names() == set()

    # make sure emitting without a callback returns False
    assert not ee.emit("data")

    # add a callback
    ee.on("data")(call_me)

    # should return True now
    assert ee.emit("data")


def test_new_listener_event():
    """The 'new_listener' event fires whenever a new listener is added."""

    call_me = Mock()
    ee = EventEmitter()

    ee.on("new_listener", call_me)

    # Should fire new_listener event
    @ee.on("event")
    def event_handler(data):
        pass

    assert ee.event_names() == {"new_listener", "event"}

    call_me.assert_called_once_with("event", event_handler)


def test_listener_removal():
    """Removing listeners removes the correct listener from an event."""

    ee = EventEmitter()

    # Some functions to pass to the EE
    def first():
        return 1

    ee.on("event", first)

    @ee.on("event")
    def second():
        return 2

    @ee.on("event")
    def third():
        return 3

    def fourth():
        return 4

    ee.on("event", fourth)

    assert ee.event_names() == {"event"}

    assert ee._events["event"] == OrderedDict(
        [(first, first), (second, second), (third, third), (fourth, fourth)]
    )

    ee.remove_listener("event", second)

    assert ee._events["event"] == OrderedDict(
        [(first, first), (third, third), (fourth, fourth)]
    )

    ee.remove_listener("event", first)
    assert ee._events["event"] == OrderedDict([(third, third), (fourth, fourth)])

    ee.remove_all_listeners("event")
    assert "event" not in ee._events["event"]


def test_listener_removal_on_emit():
    """Test that a listener removed during an emit is called inside the current
    emit cycle.
    """

    call_me = Mock()
    ee = EventEmitter()

    def should_remove():
        ee.remove_listener("remove", call_me)

    ee.on("remove", should_remove)
    ee.on("remove", call_me)

    assert ee.event_names() == {"remove"}

    ee.emit("remove")

    call_me.assert_called_once()

    call_me.reset_mock()

    # Also test with the listeners added in the opposite order
    ee = EventEmitter()
    ee.on("remove", call_me)
    ee.on("remove", should_remove)

    assert ee.event_names() == {"remove"}

    ee.emit("remove")

    call_me.assert_called_once()


def test_once():
    """Test that `once()` method works propers."""

    # very similar to "test_emit" but also makes sure that the event
    # gets removed afterwards

    call_me = Mock()
    ee = EventEmitter()

    def once_handler(data):
        assert data == "emitter is emitted!"
        call_me()

    # Tests to make sure that after event is emitted that it's gone.
    ee.once("event", once_handler)

    assert ee.event_names() == {"event"}

    ee.emit("event", "emitter is emitted!")

    call_me.assert_called_once()

    assert ee.event_names() == set()

    assert "event" not in ee._events


def test_once_removal():
    """Removal of once functions works"""

    ee = EventEmitter()

    def once_handler(data):
        pass

    handle = ee.once("event", once_handler)

    assert handle == once_handler
    assert ee.event_names() == {"event"}

    ee.remove_listener("event", handle)

    assert "event" not in ee._events
    assert ee.event_names() == set()


def test_listeners():
    """`listeners()` returns a copied list of listeners."""

    call_me = Mock()
    ee = EventEmitter()

    @ee.on("event")
    def event_handler():
        pass

    @ee.once("event")
    def once_handler():
        pass

    listeners = ee.listeners("event")

    assert listeners[0] == event_handler
    assert listeners[1] == once_handler

    # listeners is a copy, you can't mutate the innards this way
    listeners[0] = call_me

    ee.emit("event")

    call_me.assert_not_called()


def test_listeners_does_work_with_unknown_listeners():
    """`listeners()` should not throw."""
    ee = EventEmitter()
    listeners = ee.listeners("event")
    assert listeners == []


def test_properties_preserved():
    """Test that the properties of decorated functions are preserved."""

    call_me = Mock()
    call_me_also = Mock()
    ee = EventEmitter()

    @ee.on("always")
    def always_event_handler():
        """An event handler."""
        call_me()

    @ee.once("once")
    def once_event_handler():
        """Another event handler."""
        call_me_also()

    assert always_event_handler.__doc__ == "An event handler."
    assert once_event_handler.__doc__ == "Another event handler."

    always_event_handler()
    call_me.assert_called_once()

    once_event_handler()
    call_me_also.assert_called_once()

    call_me_also.reset_mock()

    # Calling the event handler directly doesn't clear the handler
    ee.emit("once")
    call_me_also.assert_called_once()