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# (C) Copyright 2005-2023 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" Test that the `sync_trait` member function of `HasTraits` instances
functions correctly.
"""
import unittest
from traits.api import (
HasTraits,
Int,
List,
push_exception_handler,
pop_exception_handler,
)
from traits.testing.unittest_tools import UnittestTools
class A(HasTraits):
t = Int
l = List(Int)
class B(HasTraits):
t = Int
u = Int
l = List(Int)
class TestSyncTraits(unittest.TestCase, UnittestTools):
def setUp(self):
push_exception_handler(lambda *args: None, reraise_exceptions=True)
def tearDown(self):
pop_exception_handler()
def test_mutual_sync(self):
""" Test that two traits can be mutually synchronized.
"""
a = A()
b = B()
a.sync_trait("t", b)
b.t = 10
self.assertEqual(a.t, b.t)
a.t = 20
self.assertEqual(b.t, a.t)
# Check that we can remove the synchronization
a.sync_trait("t", b, remove=True)
with self.assertTraitDoesNotChange(a, "t"):
b.t = 5
with self.assertTraitDoesNotChange(b, "t"):
a.t = 7
def test_sync_alias(self):
""" Test synchronization of a trait with an aliased trait.
"""
a = A()
b = B()
a.sync_trait("t", b, "u")
with self.assertTraitDoesNotChange(b, "t"):
a.t = 5
self.assertEqual(a.t, b.u)
b.u = 7
self.assertEqual(a.t, b.u)
def test_one_way_sync(self):
""" Test one-way synchronization of two traits.
"""
a = A(t=3)
b = B(t=4)
a.sync_trait("t", b, mutual=False)
self.assertEqual(b.t, 3)
a.t = 5
self.assertEqual(b.t, a.t)
with self.assertTraitDoesNotChange(a, "t"):
b.t = 7
# Remove synchronization
a.sync_trait("t", b, remove=True)
with self.assertTraitDoesNotChange(b, "t"):
a.t = 12
def test_sync_lists(self):
""" Test synchronization of list traits.
"""
a = A()
b = B()
a.sync_trait("l", b)
# Change entire list.
a.l = [1, 2, 3]
self.assertEqual(a.l, b.l)
b.l = [4, 5]
self.assertEqual(a.l, b.l)
# Change list items.
a.l = [7, 8, 9]
with self.assertTraitChanges(b, "l_items"):
a.l[-1] = 20
self.assertEqual(b.l, [7, 8, 20])
# Remove synchronization
a.sync_trait("l", b, remove=True)
with self.assertTraitDoesNotChange(a, "l"):
b.l = [7, 8]
def test_sync_lists_partial_slice(self):
""" Test synchronization of list traits when there is a partial slice.
Regression test for enthought/traits#540
"""
a = A()
b = B()
a.sync_trait("l", b)
# Change entire list.
a.l = [1, 2, 3]
self.assertEqual(a.l, b.l)
b.l = [4, 5]
self.assertEqual(a.l, b.l)
# Change list items with an empty slice.
with self.assertTraitChanges(b, "l_items"):
a.l[:] = [7]
self.assertEqual(b.l, [7])
# Change list items with a partial slice.
with self.assertTraitChanges(b, "l_items"):
a.l[:0] = [6]
self.assertEqual(b.l, [6, 7])
def test_sync_delete(self):
""" Test that deleting a synchronized trait works.
"""
a = A()
b = B()
a.sync_trait("t", b)
a.t = 5
del a
try:
# Updating `b.t` should not raise an exception due to remaining
# listeners.
b.t = 7
except Exception:
self.fail("Unexpected exception while setting sync trait.")
def test_sync_delete_one_way(self):
""" Test that deleting a one-way synchronized trait works.
(Regression test for #131).
"""
a = A()
b = B()
a.sync_trait("t", b, mutual=False)
del b
try:
a.t = 42
except Exception:
self.fail("Unexpected exception while setting sync trait.")
def test_sync_ref_cycle(self):
""" Regression test for #69.
"""
a = A()
b = B()
change_counter = [0]
def _handle_change():
change_counter[0] += 1
b.on_trait_change(_handle_change, "t")
a.sync_trait("t", b)
a.t = 17
self.assertEqual(change_counter, [1])
# Delete b and check that no more changes to b.t are recorded.
del b
a.t = 42
self.assertEqual(change_counter, [1])
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