fix: report queued work dropped at shutdown

Cancelling the scope kills the worker coroutines but does not close their
channels, so trySend kept reporting success for work nothing would ever read.
The warning that exists precisely to avoid dropping a message in silence was
therefore unreachable in the case it was written for.

Co-Authored-By: Claude <noreply@anthropic.com>

2 files changed, 20 insertions, 1 deletions

diff --git a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueue.kt b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueue.kt
index 0769823..f5e4a28 100644
--- a/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueue.kt
+++ b/platform-paper/src/main/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueue.kt
@@ -4,6 +4,7 @@ import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.channels.SendChannel
+import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import java.util.UUID
 import java.util.concurrent.ConcurrentHashMap
@@ -34,7 +35,10 @@ class PerPlayerWorkQueue(
         playerId: UUID,
         work: suspend () -> Unit,
     ) {
-        val accepted = queues.computeIfAbsent(playerId) { startWorker() }.trySend(work).isSuccess
+        // Checked rather than left to trySend: cancelling the scope kills the worker coroutines but
+        // does not close their channels, so after shutdown trySend would keep reporting success for
+        // work nothing will ever read.
+        val accepted = scope.isActive && queues.computeIfAbsent(playerId) { startWorker() }.trySend(work).isSuccess
         if (!accepted) {
             // Reachable once the scope is cancelled at shutdown, or if the player's queue is
             // released in the same tick as their command. Dropping a message in silence is worse
diff --git a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueueTest.kt b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueueTest.kt
index 95b7700..2d96cba 100644
--- a/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueueTest.kt
+++ b/platform-paper/src/test/kotlin/dev/m1sk9/lunaticChat/paper/PerPlayerWorkQueueTest.kt
@@ -3,6 +3,7 @@ package dev.m1sk9.lunaticChat.paper
 import dev.m1sk9.lunaticChat.paper.TestUtils
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withTimeout
@@ -134,4 +135,18 @@ class PerPlayerWorkQueueTest {
 
             assertTrue(logger.severeMessages.any { it.contains("Queued work failed") })
         }
+
+    @Test
+    fun `work submitted after shutdown is reported rather than silently dropped`() {
+        val logger = TestUtils.TestLogger()
+        val scope = CoroutineScope(Dispatchers.Default)
+        val queue = PerPlayerWorkQueue(scope, logger)
+        val completed = ConcurrentLinkedQueue<String>()
+
+        scope.cancel()
+        queue.submit(alice) { completed.add("never") }
+
+        assertTrue(completed.isEmpty())
+        assertTrue(logger.warningMessages.any { it.contains("their queue is closed") })
+    }
 }