1 /*
2 * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
3 */
4
5 package kotlinx.coroutines.internal
6
7 import kotlinx.coroutines.*
8 import java.util.*
9 import kotlin.coroutines.*
10
11 /**
12 * Name of the boolean property that enables using of [FastServiceLoader].
13 */
14 private const val FAST_SERVICE_LOADER_PROPERTY_NAME = "kotlinx.coroutines.fast.service.loader"
15
16 // Lazy loader for the main dispatcher
17 internal object MainDispatcherLoader {
18
19 private val FAST_SERVICE_LOADER_ENABLED = systemProp(FAST_SERVICE_LOADER_PROPERTY_NAME, true)
20
21 @JvmField
22 val dispatcher: MainCoroutineDispatcher = loadMainDispatcher()
23
loadMainDispatchernull24 private fun loadMainDispatcher(): MainCoroutineDispatcher {
25 return try {
26 val factories = if (FAST_SERVICE_LOADER_ENABLED) {
27 FastServiceLoader.loadMainDispatcherFactory()
28 } else {
29 // We are explicitly using the
30 // `ServiceLoader.load(MyClass::class.java, MyClass::class.java.classLoader).iterator()`
31 // form of the ServiceLoader call to enable R8 optimization when compiled on Android.
32 ServiceLoader.load(
33 MainDispatcherFactory::class.java,
34 MainDispatcherFactory::class.java.classLoader
35 ).iterator().asSequence().toList()
36 }
37 @Suppress("ConstantConditionIf")
38 factories.maxByOrNull { it.loadPriority }?.tryCreateDispatcher(factories)
39 ?: createMissingDispatcher()
40 } catch (e: Throwable) {
41 // Service loader can throw an exception as well
42 createMissingDispatcher(e)
43 }
44 }
45 }
46
47 /**
48 * If anything goes wrong while trying to create main dispatcher (class not found,
49 * initialization failed, etc), then replace the main dispatcher with a special
50 * stub that throws an error message on any attempt to actually use it.
51 *
52 * @suppress internal API
53 */
54 @InternalCoroutinesApi
tryCreateDispatchernull55 public fun MainDispatcherFactory.tryCreateDispatcher(factories: List<MainDispatcherFactory>): MainCoroutineDispatcher =
56 try {
57 createDispatcher(factories)
58 } catch (cause: Throwable) {
59 createMissingDispatcher(cause, hintOnError())
60 }
61
62 /** @suppress */
63 @InternalCoroutinesApi
isMissingnull64 public fun MainCoroutineDispatcher.isMissing(): Boolean =
65 // not checking `this`, as it may be wrapped in a `TestMainDispatcher`, whereas `immediate` never is.
66 this.immediate is MissingMainCoroutineDispatcher
67
68 // R8 optimization hook, not const on purpose to enable R8 optimizations via "assumenosideeffects"
69 @Suppress("MayBeConstant")
70 private val SUPPORT_MISSING = true
71
72 @Suppress(
73 "ConstantConditionIf",
74 "IMPLICIT_NOTHING_TYPE_ARGUMENT_AGAINST_NOT_NOTHING_EXPECTED_TYPE" // KT-47626
75 )
76 private fun createMissingDispatcher(cause: Throwable? = null, errorHint: String? = null) =
77 if (SUPPORT_MISSING) MissingMainCoroutineDispatcher(cause, errorHint) else
78 cause?.let { throw it } ?: throwMissingMainDispatcherException()
79
throwMissingMainDispatcherExceptionnull80 internal fun throwMissingMainDispatcherException(): Nothing {
81 throw IllegalStateException(
82 "Module with the Main dispatcher is missing. " +
83 "Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' " +
84 "and ensure it has the same version as 'kotlinx-coroutines-core'"
85 )
86 }
87
88 private class MissingMainCoroutineDispatcher(
89 private val cause: Throwable?,
90 private val errorHint: String? = null
91 ) : MainCoroutineDispatcher(), Delay {
92
93 override val immediate: MainCoroutineDispatcher get() = this
94
isDispatchNeedednull95 override fun isDispatchNeeded(context: CoroutineContext): Boolean =
96 missing()
97
98 override fun limitedParallelism(parallelism: Int): CoroutineDispatcher =
99 missing()
100
101 override suspend fun delay(time: Long) =
102 missing()
103
104 override fun invokeOnTimeout(timeMillis: Long, block: Runnable, context: CoroutineContext): DisposableHandle =
105 missing()
106
107 override fun dispatch(context: CoroutineContext, block: Runnable) =
108 missing()
109
110 override fun scheduleResumeAfterDelay(timeMillis: Long, continuation: CancellableContinuation<Unit>) =
111 missing()
112
113 private fun missing(): Nothing {
114 if (cause == null) {
115 throwMissingMainDispatcherException()
116 } else {
117 val message = "Module with the Main dispatcher had failed to initialize" + (errorHint?.let { ". $it" } ?: "")
118 throw IllegalStateException(message, cause)
119 }
120 }
121
toStringnull122 override fun toString(): String = "Dispatchers.Main[missing${if (cause != null) ", cause=$cause" else ""}]"
123 }
124
125 /**
126 * @suppress
127 */
128 @InternalCoroutinesApi
129 public object MissingMainCoroutineDispatcherFactory : MainDispatcherFactory {
130 override val loadPriority: Int
131 get() = -1
132
133 override fun createDispatcher(allFactories: List<MainDispatcherFactory>): MainCoroutineDispatcher {
134 return MissingMainCoroutineDispatcher(null)
135 }
136 }
137