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Add specific error handling for client connect #64

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Add specific error handling for client connect #64

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b522dee
feat: add specific error handling for client connect
SeanChinJunKai Mar 31, 2025
52f61e1
chore: fix typo
SeanChinJunKai Apr 1, 2025
36eafc3
feat(tests): Add unit test for client connect function
SeanChinJunKai Apr 1, 2025
8f87110
feat: remove else block to improve readability
SeanChinJunKai Apr 6, 2025
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7 changes: 6 additions & 1 deletion src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/Client.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import kotlinx.serialization.json.JsonElement
import kotlinx.serialization.json.JsonNull
import kotlinx.serialization.json.JsonObject
import kotlinx.serialization.json.JsonPrimitive
import kotlin.coroutines.cancellation.CancellationException

/**
* Options for configuring the MCP client.
Expand Down Expand Up @@ -100,7 +101,11 @@ public open class Client(
notification(InitializedNotification())
} catch (error: Throwable) {
close()
throw error
if (error !is CancellationException) {
throw IllegalStateException("Error connecting to transport: ${error.message}")
} else {
throw error
}
}
}

Expand Down
63 changes: 60 additions & 3 deletions src/jvmTest/kotlin/client/ClientTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@ import io.modelcontextprotocol.kotlin.sdk.CreateMessageResult
import io.modelcontextprotocol.kotlin.sdk.EmptyJsonObject
import io.modelcontextprotocol.kotlin.sdk.Implementation
import InMemoryTransport
import io.mockk.coEvery
import io.mockk.spyk
import io.modelcontextprotocol.kotlin.sdk.InitializeRequest
import io.modelcontextprotocol.kotlin.sdk.InitializeResult
import io.modelcontextprotocol.kotlin.sdk.JSONRPCMessage
Expand Down Expand Up @@ -49,13 +51,13 @@ import kotlin.test.fail
class ClientTest {
@Test
fun `should initialize with matching protocol version`() = runTest {
var initialied = false
var initialised = false
val clientTransport = object : AbstractTransport() {
override suspend fun start() {}

override suspend fun send(message: JSONRPCMessage) {
if (message !is JSONRPCRequest) return
initialied = true
initialised = true
val result = InitializeResult(
protocolVersion = LATEST_PROTOCOL_VERSION,
capabilities = ServerCapabilities(),
Expand Down Expand Up @@ -90,7 +92,7 @@ class ClientTest {
)

client.connect(clientTransport)
assertTrue(initialied)
assertTrue(initialised)
}

@Test
Expand Down Expand Up @@ -189,6 +191,61 @@ class ClientTest {
assertTrue(closed)
}

@Test
fun `should reject due to non cancellation exception`() = runTest {
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Can we add test for the case when a Cancellation exception is thrown?

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@SeanChinJunKai SeanChinJunKai Apr 6, 2025 •
edited
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@ribhavpahuja can i ask how will cancellation exception be thrown in this case? wanted to clarify before adding a test

var closed = false
val clientTransport = object : AbstractTransport() {
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I see clientTransport is very similar to the one in the previous test. should we create a test utility?

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i will look into this

override suspend fun start() {}

override suspend fun send(message: JSONRPCMessage) {
if (message !is JSONRPCRequest) return
check(message.method == Method.Defined.Initialize.value)

val result = InitializeResult(
protocolVersion = LATEST_PROTOCOL_VERSION,
capabilities = ServerCapabilities(),
serverInfo = Implementation(
name = "test",
version = "1.0"
)
)

val response = JSONRPCResponse(
id = message.id,
result = result
)

_onMessage.invoke(response)
}

override suspend fun close() {
closed = true
}
}

val mockClient = spyk(
Client(
clientInfo = Implementation(
name = "test client",
version = "1.0"
),
options = ClientOptions()
)
)

coEvery{
mockClient.request<InitializeResult>(any())
} throws IllegalStateException("Test error")

val exception = assertFailsWith<IllegalStateException> {
mockClient.connect(clientTransport)
}

assertEquals("Error connecting to transport: Test error", exception.message)

assertTrue(closed)
}

@Test
fun `should respect server capabilities`() = runTest {
val serverOptions = ServerOptions(
Expand Down