1 /*
2 * Copyright 2016-2020 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.maxBy { 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 = this is MissingMainCoroutineDispatcher
65
66 // R8 optimization hook, not const on purpose to enable R8 optimizations via "assumenosideeffects"
67 @Suppress("MayBeConstant")
68 private val SUPPORT_MISSING = true
69
70 @Suppress("ConstantConditionIf")
71 private fun createMissingDispatcher(cause: Throwable? = null, errorHint: String? = null) =
72 if (SUPPORT_MISSING) MissingMainCoroutineDispatcher(cause, errorHint) else
73 cause?.let { throw it } ?: throwMissingMainDispatcherException()
74
throwMissingMainDispatcherExceptionnull75 internal fun throwMissingMainDispatcherException(): Nothing {
76 throw IllegalStateException(
77 "Module with the Main dispatcher is missing. " +
78 "Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' " +
79 "and ensure it has the same version as 'kotlinx-coroutines-core'"
80 )
81 }
82
83 private class MissingMainCoroutineDispatcher(
84 private val cause: Throwable?,
85 private val errorHint: String? = null
86 ) : MainCoroutineDispatcher(), Delay {
87
88 override val immediate: MainCoroutineDispatcher get() = this
89
isDispatchNeedednull90 override fun isDispatchNeeded(context: CoroutineContext): Boolean =
91 missing()
92
93 override suspend fun delay(time: Long) =
94 missing()
95
96 override fun invokeOnTimeout(timeMillis: Long, block: Runnable, context: CoroutineContext): DisposableHandle =
97 missing()
98
99 override fun dispatch(context: CoroutineContext, block: Runnable) =
100 missing()
101
102 override fun scheduleResumeAfterDelay(timeMillis: Long, continuation: CancellableContinuation<Unit>) =
103 missing()
104
105 private fun missing(): Nothing {
106 if (cause == null) {
107 throwMissingMainDispatcherException()
108 } else {
109 val message = "Module with the Main dispatcher had failed to initialize" + (errorHint?.let { ". $it" } ?: "")
110 throw IllegalStateException(message, cause)
111 }
112 }
113
toStringnull114 override fun toString(): String = "Dispatchers.Main[missing${if (cause != null) ", cause=$cause" else ""}]"
115 }
116
117 /**
118 * @suppress
119 */
120 @InternalCoroutinesApi
121 public object MissingMainCoroutineDispatcherFactory : MainDispatcherFactory {
122 override val loadPriority: Int
123 get() = -1
124
125 override fun createDispatcher(allFactories: List<MainDispatcherFactory>): MainCoroutineDispatcher {
126 return MissingMainCoroutineDispatcher(null)
127 }
128 }
129