def test_combine_latest():
a = Stream()
b = Stream()
c = a.combine_latest(b)
d = a.combine_latest(b, emit_on=[a, b])
L = c.sink_to_list()
L2 = d.sink_to_list()
a.emit(1)
a.emit(2)
b.emit('a')
a.emit(3)
b.emit('b')
assert L == [(2, 'a'), (3, 'a'), (3, 'b')]
assert L2 == [(2, 'a'), (3, 'a'), (3, 'b')]
def test_connect_discombine_latest():
a = Stream()
b = Stream()
c = Stream()
x = a.combine_latest(b, c, emit_on=a)
L = x.sink_to_list()
c.disconnect(x)
b.emit(1)
c.emit(1)
a.emit(1)
assert L == [(1, 1)]
def test_combine_latest_metadata():
a = Stream()
b = Stream()
L = metadata(a.combine_latest(b)).sink_to_list()
a.emit(1, metadata=[{'v': 1}])
b.emit(2, metadata=[{'v': 2}])
b.emit(3)
b.emit(4, metadata=[{'v': 4}])
assert L == [
[{'v': 1}, {'v': 2}], # first emit when 2 is introduced
[{'v': 1}], # 3 has no metadata but it replaces the value on 'b'
[{'v': 1}, {'v': 4}] # 4 replaces the value without metadata on 'b'
]
def test_combine_latest_emit_on_stream():
a = Stream()
b = Stream()
c = a.combine_latest(b, emit_on=0)
L = c.sink_to_list()
a.emit(1)
b.emit('a')
a.emit(2)
a.emit(3)
b.emit('b')
a.emit(4)
assert L == [(2, 'a'), (3, 'a'), (4, 'b')]
def test_combine_latest_ref_counts():
a = Stream()
b = Stream()
_ = a.combine_latest(b)
ref1 = RefCounter()
a.emit(1, metadata=[{'ref': ref1}])
assert ref1.count == 1
# The new value kicks out the old value
ref2 = RefCounter()
a.emit(2, metadata=[{'ref': ref2}])
assert ref1.count == 0
assert ref2.count == 1
# The value on stream a is still retained and the value on stream b is new
ref3 = RefCounter()
b.emit(3, metadata=[{'ref': ref3}])
assert ref2.count == 1
assert ref3.count == 1
