def test_zip_latest_ref_counts():
a = Stream()
b = Stream()
_ = a.zip_latest(b)
ref1 = RefCounter()
a.emit(1, metadata=[{'ref': ref1}])
assert ref1.count == 1 # Retained until stream b has a value
# The lossless stream is never retained if all upstreams have a value
ref2 = RefCounter()
b.emit(2, metadata=[{'ref': ref2}])
assert ref1.count == 0
assert ref2.count == 1
# Kick out the stream b value and verify it has zero references
ref3 = RefCounter()
b.emit(3, metadata=[{'ref': ref3}])
assert ref2.count == 0
assert ref3.count == 1
# Verify the lossless value is not retained, but the lossy value is
ref4 = RefCounter()
a.emit(3, metadata=[{'ref': ref4}])
assert ref3.count == 1
assert ref4.count == 0
def test_zip_latest_reverse():
a = Stream()
b = Stream()
c = a.zip_latest(b)
L = c.sink_to_list()
b.emit('a')
a.emit(1)
a.emit(2)
a.emit(3)
b.emit('b')
a.emit(4)
assert L == [(1, 'a'), (2, 'a'), (3, 'a'), (4, 'b')]
def test_triple_zip_latest():
from streamz.core import Stream
s1 = Stream()
s2 = Stream()
s3 = Stream()
s_simple = s1.zip_latest(s2, s3)
L_simple = s_simple.sink_to_list()
s1.emit(1)
s2.emit('I')
s2.emit("II")
s1.emit(2)
s2.emit("III")
s3.emit('a')
s3.emit('b')
s1.emit(3)
assert L_simple == [(1, 'III', 'a'), (2, 'III', 'a'), (3, 'III', 'b')]
def test_zip_latest():
a = Stream()
b = Stream()
c = a.zip_latest(b)
d = a.combine_latest(b, emit_on=a)
L = c.sink_to_list()
L2 = d.sink_to_list()
a.emit(1)
a.emit(2)
b.emit('a')
b.emit('b')
a.emit(3)
assert L == [(1, 'a'), (2, 'a'), (3, 'b')]
assert L2 == [(3, 'b')]
def test_zip_latest_metadata():
a = Stream()
b = Stream()
L = metadata(a.zip_latest(b)).sink_to_list()
a.emit(1, metadata=[{'v': 1}])
b.emit(2, metadata=[{'v': 2}])
a.emit(3)
b.emit(4, metadata=[{'v': 4}])
assert L == [
[{
'v': 1
}, {
'v': 2
}], # the first emit when 2 is introduced
[{
'v': 2
}] # 3 has no metadata
]