Add concurrency control to event listeners

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/internal/InternalEventListeners.kt

@@ -34,22 +34,33 @@ fun <L : Listener<E>, E : Event> KClass<out E>.subscribeInternal(listener: L): L
 @Suppress("FunctionName")
 internal fun <E : Event> CoroutineScope.Handler(
     coroutineContext: CoroutineContext,
+    concurrencyKind: Listener.ConcurrencyKind,
     handler: suspend (E) -> ListeningStatus
 ): Handler<E> {
     @OptIn(ExperimentalCoroutinesApi::class) // don't remove
     val context = this.newCoroutineContext(coroutineContext)
-    return Handler(context[Job], context, handler)
+    return Handler(context[Job], context, handler, concurrencyKind)
 }
 
-private inline fun inline(block: () -> Unit) = block()
 /**
  * 事件处理器.
  */
 @PublishedApi
 internal class Handler<in E : Event>
-@PublishedApi internal constructor(parentJob: Job?, private val subscriberContext: CoroutineContext, @JvmField val handler: suspend (E) -> ListeningStatus) :
+@PublishedApi internal constructor(
+    parentJob: Job?,
+    private val subscriberContext: CoroutineContext,
+    @JvmField val handler: suspend (E) -> ListeningStatus,
+    override val concurrencyKind: Listener.ConcurrencyKind
+) :
     Listener<E>, CompletableJob by Job(parentJob) {
 
+    @MiraiInternalAPI
+    val lock: Mutex? = when (concurrencyKind) {
+        Listener.ConcurrencyKind.CONCURRENT -> null
+        Listener.ConcurrencyKind.LOCKED -> Mutex()
+    }
+
     @OptIn(MiraiDebugAPI::class)
     override suspend fun onEvent(event: E): ListeningStatus {
         if (isCompleted || isCancelled) return ListeningStatus.STOPPED
@@ -60,7 +71,7 @@ internal class Handler<in E : Event>
         } catch (e: Throwable) {
             subscriberContext[CoroutineExceptionHandler]?.handleException(subscriberContext, e)
                 ?: coroutineContext[CoroutineExceptionHandler]?.handleException(subscriberContext, e)
-                ?: inline {
+                ?: kotlin.run {
                     @Suppress("DEPRECATION")
                     MiraiLogger.warning(
                         """Event processing: An exception occurred but no CoroutineExceptionHandler found, 
@@ -75,9 +86,6 @@ internal class Handler<in E : Event>
             ListeningStatus.LISTENING
         }
     }
-
-    @MiraiInternalAPI
-    override val lock: Mutex = Mutex()
 }
 
 /**
@@ -161,7 +169,13 @@ private fun <E : Event> CoroutineScope.callAndRemoveIfRequired(event: E, listene
     listeners.forEachNode { node ->
         launch {
             val listener = node.nodeValue
-            listener.lock.withLock {
+            if (listener.concurrencyKind == Listener.ConcurrencyKind.LOCKED) {
+                (listener as Handler).lock!!.withLock {
+                    if (!node.isRemoved() && listener.onEvent(event) == ListeningStatus.STOPPED) {
+                        listeners.remove(listener) // atomic remove
+                    }
+                }
+            } else {
                 if (!node.isRemoved() && listener.onEvent(event) == ListeningStatus.STOPPED) {
                     listeners.remove(listener) // atomic remove
                 }

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/subscriber.kt

@@ -52,11 +52,23 @@ enum class ListeningStatus {
  * 取消监听: [complete]
  */
 interface Listener<in E : Event> : CompletableJob {
+
+    enum class ConcurrencyKind {
+        /**
+         * 并发地同时处理多个事件, 但无法保证 [onEvent] 返回 [ListeningStatus.STOPPED] 后立即停止事件监听.
+         */
+        CONCURRENT,
+
+        /**
+         * 使用 [Mutex] 保证同一时刻只处理一个事件.
+         */
+        LOCKED
+    }
+
     /**
-     * [onEvent] 的锁
+     * 并发类型
      */
-    @MiraiInternalAPI
-    val lock: Mutex
+    val concurrencyKind: ConcurrencyKind
 
     suspend fun onEvent(event: E): ListeningStatus
 }
@@ -121,9 +133,10 @@ interface Listener<in E : Event> : CompletableJob {
 @OptIn(MiraiInternalAPI::class)
 inline fun <reified E : Event> CoroutineScope.subscribe(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
+    concurrency: Listener.ConcurrencyKind = Listener.ConcurrencyKind.LOCKED,
     noinline handler: suspend E.(E) -> ListeningStatus
 ): Listener<E> =
-    E::class.subscribeInternal(Handler(coroutineContext) { it.handler(it); })
+    E::class.subscribeInternal(Handler(coroutineContext, concurrency) { it.handler(it); })
 
 /**
  * 在指定的 [CoroutineScope] 下订阅所有 [E] 及其子类事件.
@@ -139,12 +152,17 @@ inline fun <reified E : Event> CoroutineScope.subscribe(
 @OptIn(MiraiInternalAPI::class, ExperimentalContracts::class)
 inline fun <reified E : Event> CoroutineScope.subscribeAlways(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
+    concurrency: Listener.ConcurrencyKind = Listener.ConcurrencyKind.LOCKED,
     noinline listener: suspend E.(E) -> Unit
 ): Listener<E> {
     contract {
         callsInPlace(listener, InvocationKind.UNKNOWN)
     }
-    return E::class.subscribeInternal(Handler(coroutineContext) { it.listener(it); ListeningStatus.LISTENING })
+    return E::class.subscribeInternal(
+        Handler(
+            coroutineContext,
+            concurrency
+        ) { it.listener(it); ListeningStatus.LISTENING })
 }
 
 /**
@@ -163,7 +181,11 @@ inline fun <reified E : Event> CoroutineScope.subscribeOnce(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
     noinline listener: suspend E.(E) -> Unit
 ): Listener<E> =
-    E::class.subscribeInternal(Handler(coroutineContext) { it.listener(it); ListeningStatus.STOPPED })
+    E::class.subscribeInternal(
+        Handler(
+            coroutineContext,
+            Listener.ConcurrencyKind.LOCKED
+        ) { it.listener(it); ListeningStatus.STOPPED })
 
 
 //
@@ -187,9 +209,14 @@ inline fun <reified E : Event> CoroutineScope.subscribeOnce(
 @OptIn(MiraiInternalAPI::class)
 inline fun <reified E : BotEvent> Bot.subscribe(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
+    concurrency: Listener.ConcurrencyKind = Listener.ConcurrencyKind.LOCKED,
     noinline handler: suspend E.(E) -> ListeningStatus
 ): Listener<E> =
-    E::class.subscribeInternal(Handler(coroutineContext) { if (it.bot === this) it.handler(it) else ListeningStatus.LISTENING })
+    E::class.subscribeInternal(
+        Handler(
+            coroutineContext,
+            concurrency
+        ) { if (it.bot === this) it.handler(it) else ListeningStatus.LISTENING })
 
 
 /**
@@ -207,9 +234,14 @@ inline fun <reified E : BotEvent> Bot.subscribe(
 @OptIn(MiraiInternalAPI::class)
 inline fun <reified E : BotEvent> Bot.subscribeAlways(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
+    concurrency: Listener.ConcurrencyKind = Listener.ConcurrencyKind.CONCURRENT,
     noinline listener: suspend E.(E) -> Unit
 ): Listener<E> {
-    return E::class.subscribeInternal(Handler(coroutineContext) { if (it.bot === this) it.listener(it); ListeningStatus.LISTENING })
+    return E::class.subscribeInternal(
+        Handler(
+            coroutineContext,
+            concurrency
+        ) { if (it.bot === this) it.listener(it); ListeningStatus.LISTENING })
 }
 
 /**
@@ -229,7 +261,7 @@ inline fun <reified E : BotEvent> Bot.subscribeOnce(
     coroutineContext: CoroutineContext = EmptyCoroutineContext,
     noinline listener: suspend E.(E) -> Unit
 ): Listener<E> =
-    E::class.subscribeInternal(Handler(coroutineContext) {
+    E::class.subscribeInternal(Handler(coroutineContext, Listener.ConcurrencyKind.LOCKED) {
         if (it.bot === this) {
             it.listener(it)
             ListeningStatus.STOPPED

mirai-core/src/jvmMain/kotlin/net/mamoe/mirai/event/internal/EventInternalJvm.kt

@@ -7,6 +7,8 @@
  * https://github.com/mamoe/mirai/blob/master/LICENSE
  */
 
+@file:Suppress("unused")
+
 package net.mamoe.mirai.event.internal
 
 import kotlinx.coroutines.CoroutineScope
@@ -21,11 +23,19 @@ import kotlin.coroutines.EmptyCoroutineContext
 @MiraiInternalAPI
 @Suppress("FunctionName")
 fun <E : Event> Class<E>._subscribeEventForJaptOnly(scope: CoroutineScope, onEvent: Function<E, ListeningStatus>): Listener<E> {
-    return this.kotlin.subscribeInternal(scope.Handler(EmptyCoroutineContext) { onEvent.apply(it) })
+    return this.kotlin.subscribeInternal(
+        scope.Handler(
+            EmptyCoroutineContext,
+            Listener.ConcurrencyKind.CONCURRENT
+        ) { onEvent.apply(it) })
 }
 
 @MiraiInternalAPI
 @Suppress("FunctionName")
 fun <E : Event> Class<E>._subscribeEventForJaptOnly(scope: CoroutineScope, onEvent: Consumer<E>): Listener<E> {
-    return this.kotlin.subscribeInternal(scope.Handler(EmptyCoroutineContext) { onEvent.accept(it); ListeningStatus.LISTENING; })
+    return this.kotlin.subscribeInternal(
+        scope.Handler(
+            EmptyCoroutineContext,
+            Listener.ConcurrencyKind.CONCURRENT
+        ) { onEvent.accept(it); ListeningStatus.LISTENING; })
 }
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