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fix: handle CancellationException in WebSocketTransport #663

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fix: handle CancellationException in WebSocketTransport #663

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c4fa2df
Handle `CancellationException` gracefully and enable ignored tests
devcrocod Apr 1, 2026
c39d4ab
Merge branch 'main' into devcrocod/websocket-transport-cancellation
devcrocod Apr 14, 2026
3cfd7f0
Merge branch 'main' into devcrocod/websocket-transport-cancellation
devcrocod Apr 29, 2026
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8 changes: 4 additions & 4 deletions ...tlin/sdk/client/WebSocketTransportTest.kt → ...tlin/sdk/client/WebSocketTransportTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -6,12 +6,13 @@ import io.modelcontextprotocol.kotlin.sdk.server.mcpWebSocket
import io.modelcontextprotocol.kotlin.sdk.server.mcpWebSocketTransport
import io.modelcontextprotocol.kotlin.sdk.shared.BaseTransportTest
import kotlinx.coroutines.CompletableDeferred
import kotlin.test.Ignore
import kotlin.test.Test
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.Timeout
import java.util.concurrent.TimeUnit

@Timeout(30, unit = TimeUnit.SECONDS)
class WebSocketTransportTest : BaseTransportTest() {
@Test
@Ignore // "Test disabled for investigation #17"
fun `should start then close cleanly`() = testApplication {
install(WebSockets)
routing {
Expand All @@ -26,7 +27,6 @@ class WebSocketTransportTest : BaseTransportTest() {
}

@Test
@Ignore // "Test disabled for investigation #17"
fun `should read messages`() = testApplication {
val clientFinished = CompletableDeferred<Unit>()

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5 changes: 2 additions & 3 deletions .../src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/shared/WebSocketMcpTransport.kt
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Expand Up @@ -7,9 +7,9 @@ import io.ktor.websocket.close
import io.ktor.websocket.readText
import io.modelcontextprotocol.kotlin.sdk.types.JSONRPCMessage
import io.modelcontextprotocol.kotlin.sdk.types.McpJson
import kotlinx.coroutines.CancellationException
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Copilot AI Apr 29, 2026

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This file now imports both kotlinx.coroutines.CancellationException and kotlin.coroutines.cancellation.CancellationException, which will either be ambiguous at compile time or lead to inconsistent type checks (e.g., the catch (e: CancellationException) and it !is CancellationException checks). Remove one import and consistently use the project-standard kotlin.coroutines.cancellation.CancellationException (as used in other core transport code).

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import kotlinx.coroutines.CancellationException

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import kotlinx.coroutines.CoroutineName
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import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.InternalCoroutinesApi
import kotlinx.coroutines.SupervisorJob
import kotlinx.coroutines.channels.ClosedReceiveChannelException
import kotlinx.coroutines.job
Expand Down Expand Up @@ -81,9 +81,8 @@ public abstract class WebSocketMcpTransport : AbstractTransport() {
}
}

@OptIn(InternalCoroutinesApi::class)
session.coroutineContext.job.invokeOnCompletion {
if (it != null) {
if (it != null && it !is CancellationException) {
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_onError.invoke(it)
} else {
invokeOnCloseCallback()
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