1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
/*
* Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
package kotlinx.coroutines.flow
import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*
import kotlin.test.*
class ShareInTest : TestBase() {
@Test
fun testReplay0Eager() = runTest {
expect(1)
val flow = flowOf("OK")
val shared = flow.shareIn(this, SharingStarted.Eagerly)
yield() // actually start sharing
// all subscribers miss "OK"
val jobs = List(10) {
shared.onEach { expectUnreached() }.launchIn(this)
}
yield() // ensure nothing is collected
jobs.forEach { it.cancel() }
finish(2)
}
@Test
fun testReplay0Lazy() = testReplayZeroOrOne(0)
@Test
fun testReplay1Lazy() = testReplayZeroOrOne(1)
private fun testReplayZeroOrOne(replay: Int) = runTest {
expect(1)
val doneBarrier = Job()
val flow = flow {
expect(2)
emit("OK")
doneBarrier.join()
emit("DONE")
}
val sharingJob = Job()
val shared = flow.shareIn(this + sharingJob, started = SharingStarted.Lazily, replay = replay)
yield() // should not start sharing
// first subscriber gets "OK", other subscribers miss "OK"
val n = 10
val replayOfs = replay * (n - 1)
val subscriberJobs = List(n) { index ->
val subscribedBarrier = Job()
val job = shared
.onSubscription {
subscribedBarrier.complete()
}
.onEach { value ->
when (value) {
"OK" -> {
expect(3 + index)
if (replay == 0) { // only the first subscriber collects "OK" without replay
assertEquals(0, index)
}
}
"DONE" -> {
expect(4 + index + replayOfs)
}
else -> expectUnreached()
}
}
.takeWhile { it != "DONE" }
.launchIn(this)
subscribedBarrier.join() // wait until the launched job subscribed before launching the next one
job
}
doneBarrier.complete()
subscriberJobs.joinAll()
expect(4 + n + replayOfs)
sharingJob.cancel()
finish(5 + n + replayOfs)
}
@Test
fun testUpstreamCompleted() =
testUpstreamCompletedOrFailed(failed = false)
@Test
fun testUpstreamFailed() =
testUpstreamCompletedOrFailed(failed = true)
private fun testUpstreamCompletedOrFailed(failed: Boolean) = runTest {
val emitted = Job()
val terminate = Job()
val sharingJob = CompletableDeferred<Unit>()
val upstream = flow {
emit("OK")
emitted.complete()
terminate.join()
if (failed) throw TestException()
}
val shared = upstream.shareIn(this + sharingJob, SharingStarted.Eagerly, 1)
assertEquals(emptyList(), shared.replayCache)
emitted.join() // should start sharing, emit & cache
assertEquals(listOf("OK"), shared.replayCache)
terminate.complete()
sharingJob.complete(Unit)
sharingJob.join() // should complete sharing
assertEquals(listOf("OK"), shared.replayCache) // cache is still there
if (failed) {
assertTrue(sharingJob.getCompletionExceptionOrNull() is TestException)
} else {
assertNull(sharingJob.getCompletionExceptionOrNull())
}
}
@Test
fun testWhileSubscribedBasic() =
testWhileSubscribed(1, SharingStarted.WhileSubscribed())
@Test
fun testWhileSubscribedCustomAtLeast1() =
testWhileSubscribed(1, SharingStarted.WhileSubscribedAtLeast(1))
@Test
fun testWhileSubscribedCustomAtLeast2() =
testWhileSubscribed(2, SharingStarted.WhileSubscribedAtLeast(2))
@OptIn(ExperimentalStdlibApi::class)
private fun testWhileSubscribed(threshold: Int, started: SharingStarted) = runTest {
expect(1)
val flowState = FlowState()
val n = 3 // max number of subscribers
val log = Channel<String>(2 * n)
suspend fun checkStartTransition(subscribers: Int) {
when (subscribers) {
in 0 until threshold -> assertFalse(flowState.started)
threshold -> {
flowState.awaitStart() // must eventually start the flow
for (i in 1..threshold) {
assertEquals("sub$i: OK", log.receive()) // threshold subs must receive the values
}
}
in threshold + 1..n -> assertTrue(flowState.started)
}
}
suspend fun checkStopTransition(subscribers: Int) {
when (subscribers) {
in threshold + 1..n -> assertTrue(flowState.started)
threshold - 1 -> flowState.awaitStop() // upstream flow must be eventually stopped
in 0..threshold - 2 -> assertFalse(flowState.started) // should have stopped already
}
}
val flow = flow {
flowState.track {
emit("OK")
delay(Long.MAX_VALUE) // await forever, will get cancelled
}
}
val shared = flow.shareIn(this, started)
repeat(5) { // repeat scenario a few times
yield()
assertFalse(flowState.started) // flow is not running even if we yield
// start 3 subscribers
val subs = ArrayList<Job>()
for (i in 1..n) {
subs += shared
.onEach { value -> // only the first threshold subscribers get the value
when (i) {
in 1..threshold -> log.offer("sub$i: $value")
else -> expectUnreached()
}
}
.onCompletion { log.offer("sub$i: completion") }
.launchIn(this)
checkStartTransition(i)
}
// now cancel all subscribers
for (i in 1..n) {
subs.removeFirst().cancel() // cancel subscriber
assertEquals("sub$i: completion", log.receive()) // subscriber shall shutdown
checkStopTransition(n - i)
}
}
coroutineContext.cancelChildren() // cancel sharing job
finish(2)
}
@Suppress("TestFunctionName")
private fun SharingStarted.Companion.WhileSubscribedAtLeast(threshold: Int) =
SharingStarted { subscriptionCount ->
subscriptionCount.map { if (it >= threshold) SharingCommand.START else SharingCommand.STOP }
}
private class FlowState {
private val timeLimit = 10000L
private val _started = MutableStateFlow(false)
val started: Boolean get() = _started.value
fun start() = check(_started.compareAndSet(expect = false, update = true))
fun stop() = check(_started.compareAndSet(expect = true, update = false))
suspend fun awaitStart() = withTimeout(timeLimit) { _started.first { it } }
suspend fun awaitStop() = withTimeout(timeLimit) { _started.first { !it } }
}
private suspend fun FlowState.track(block: suspend () -> Unit) {
start()
try {
block()
} finally {
stop()
}
}
}
|
