Add streamable http client transport (#147)
* feat: add streamable http client * update StreamableHttpClientTransport * improve StreamableHttpClientTransport handling of headers, event parsing, and session termination * add simple tests for StreamableClient and fix send * add client mocking * add notification e2e tests --------- Co-authored-by: Zach Tang <zachtangoj@gmail.com>
This commit is contained in:
Pavel Gorgulov
GitHub
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1 changed files with 788 additions and 1 deletions
369
src/jvmTest/kotlin/client/StreamableHttpClientTransportTest.kt
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369
src/jvmTest/kotlin/client/StreamableHttpClientTransportTest.kt
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package client
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import io.ktor.client.HttpClient
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import io.ktor.client.engine.mock.MockEngine
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import io.ktor.client.engine.mock.MockRequestHandler
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import io.ktor.client.engine.mock.respond
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import io.ktor.client.plugins.sse.SSE
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import io.ktor.http.ContentType
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import io.ktor.http.HttpHeaders
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import io.ktor.http.HttpMethod
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import io.ktor.http.HttpStatusCode
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import io.ktor.http.content.TextContent
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import io.ktor.http.headersOf
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import io.ktor.utils.io.ByteReadChannel
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import io.modelcontextprotocol.kotlin.sdk.JSONRPCMessage
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import io.modelcontextprotocol.kotlin.sdk.JSONRPCNotification
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import io.modelcontextprotocol.kotlin.sdk.JSONRPCRequest
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import io.modelcontextprotocol.kotlin.sdk.RequestId
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import io.modelcontextprotocol.kotlin.sdk.client.StreamableHttpClientTransport
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import io.modelcontextprotocol.kotlin.sdk.shared.McpJson
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import kotlinx.coroutines.delay
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import kotlinx.coroutines.test.runTest
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import kotlinx.serialization.json.JsonObject
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import kotlinx.serialization.json.JsonPrimitive
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import kotlinx.serialization.json.buildJsonObject
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import org.junit.jupiter.api.assertDoesNotThrow
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import kotlin.test.Ignore
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import kotlin.test.Test
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import kotlin.test.assertEquals
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import kotlin.test.assertNull
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import kotlin.test.assertTrue
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import kotlin.time.Duration.Companion.seconds
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class StreamableHttpClientTransportTest {
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private fun createTransport(handler: MockRequestHandler): StreamableHttpClientTransport {
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val mockEngine = MockEngine(handler)
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val httpClient = HttpClient(mockEngine) {
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install(SSE) {
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reconnectionTime = 1.seconds
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}
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}
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return StreamableHttpClientTransport(httpClient, url = "http://localhost:8080/mcp")
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}
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@Test
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fun testSendJsonRpcMessage() = runTest {
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val message = JSONRPCRequest(
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id = RequestId.StringId("test-id"),
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method = "test",
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params = buildJsonObject { }
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)
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val transport = createTransport { request ->
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assertEquals(HttpMethod.Post, request.method)
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assertEquals("http://localhost:8080/mcp", request.url.toString())
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assertEquals(ContentType.Application.Json, request.body.contentType)
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val body = (request.body as TextContent).text
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val decodedMessage = McpJson.decodeFromString<JSONRPCMessage>(body)
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assertEquals(message, decodedMessage)
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respond(
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content = "",
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status = HttpStatusCode.Accepted
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)
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}
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transport.start()
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transport.send(message)
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transport.close()
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}
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@Test
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fun testStoreSessionId() = runTest {
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val initMessage = JSONRPCRequest(
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id = RequestId.StringId("test-id"),
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method = "initialize",
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params = buildJsonObject {
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put("clientInfo", buildJsonObject {
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put("name", JsonPrimitive("test-client"))
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put("version", JsonPrimitive("1.0"))
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})
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put("protocolVersion", JsonPrimitive("2025-06-18"))
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}
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)
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val transport = createTransport { request ->
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when (val msg = McpJson.decodeFromString<JSONRPCMessage>((request.body as TextContent).text)) {
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is JSONRPCRequest if msg.method == "initialize" -> respond(
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content = "", status = HttpStatusCode.OK,
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headers = headersOf("mcp-session-id", "test-session-id")
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)
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is JSONRPCNotification if msg.method == "test" -> {
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assertEquals("test-session-id", request.headers["mcp-session-id"])
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respond(
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content = "",
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status = HttpStatusCode.Accepted
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)
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}
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else -> error("Unexpected message: $msg")
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}
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}
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transport.start()
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transport.send(initMessage)
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assertEquals("test-session-id", transport.sessionId)
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transport.send(JSONRPCNotification(method = "test"))
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transport.close()
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}
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@Test
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fun testTerminateSession() = runTest {
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// transport.sessionId = "test-session-id"
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val transport = createTransport { request ->
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assertEquals(HttpMethod.Delete, request.method)
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assertEquals("test-session-id", request.headers["mcp-session-id"])
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respond(
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content = "",
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status = HttpStatusCode.OK
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)
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}
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transport.start()
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transport.terminateSession()
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assertNull(transport.sessionId)
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transport.close()
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}
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@Test
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fun testTerminateSessionHandle405() = runTest {
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// transport.sessionId = "test-session-id"
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val transport = createTransport { request ->
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assertEquals(HttpMethod.Delete, request.method)
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respond(
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content = "",
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status = HttpStatusCode.MethodNotAllowed
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)
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}
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transport.start()
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// Should not throw for 405
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assertDoesNotThrow {
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transport.terminateSession()
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}
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// Session ID should still be cleared
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assertNull(transport.sessionId)
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transport.close()
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}
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@Test
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fun testProtocolVersionHeader() = runTest {
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val transport = createTransport { request ->
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assertEquals("2025-06-18", request.headers["mcp-protocol-version"])
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respond(
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content = "",
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status = HttpStatusCode.Accepted
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)
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}
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transport.protocolVersion = "2025-06-18"
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transport.start()
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transport.send(JSONRPCNotification(method = "test"))
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transport.close()
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}
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@Ignore("Engine doesn't support SSECapability: https://youtrack.jetbrains.com/issue/KTOR-8177/MockEngine-Add-SSE-support")
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@Test
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fun testNotificationSchemaE2E() = runTest {
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val receivedMessages = mutableListOf<JSONRPCMessage>()
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var sseStarted = false
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val transport = createTransport { request ->
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when (request.method) {
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HttpMethod.Post if request.body.toString().contains("notifications/initialized") -> {
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respond(
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content = "",
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status = HttpStatusCode.Accepted,
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headers = headersOf("mcp-session-id", "notification-test-session")
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)
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}
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// Handle SSE connection
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HttpMethod.Get -> {
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sseStarted = true
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val sseContent = buildString {
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// Server sends various notifications
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appendLine("event: message")
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appendLine("id: 1")
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appendLine("""data: {"jsonrpc":"2.0","method":"notifications/progress","params":{"progressToken":"upload-123","progress":50,"total":100}}""")
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appendLine()
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appendLine("event: message")
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appendLine("id: 2")
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appendLine("""data: {"jsonrpc":"2.0","method":"notifications/resources/list_changed"}""")
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appendLine()
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appendLine("event: message")
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appendLine("id: 3")
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appendLine("""data: {"jsonrpc":"2.0","method":"notifications/tools/list_changed"}""")
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appendLine()
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}
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respond(
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content = ByteReadChannel(sseContent),
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status = HttpStatusCode.OK,
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headers = headersOf(
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HttpHeaders.ContentType, ContentType.Text.EventStream.toString()
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)
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)
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}
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// Handle regular notifications
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HttpMethod.Post -> {
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respond(
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content = "",
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status = HttpStatusCode.Accepted
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)
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}
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else -> respond("", HttpStatusCode.OK)
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}
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}
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transport.onMessage { message ->
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receivedMessages.add(message)
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}
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transport.start()
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// Test 1: Send initialized notification to trigger SSE
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val initializedNotification = JSONRPCNotification(
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method = "notifications/initialized",
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params = buildJsonObject {
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put("protocolVersion", JsonPrimitive("1.0"))
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put("capabilities", buildJsonObject {
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put("tools", JsonPrimitive(true))
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put("resources", JsonPrimitive(true))
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})
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}
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)
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transport.send(initializedNotification)
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// Verify SSE was triggered
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assertTrue(sseStarted, "SSE should start after initialized notification")
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// Test 2: Verify received notifications
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assertEquals(3, receivedMessages.size)
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assertTrue(receivedMessages.all { it is JSONRPCNotification })
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val notifications = receivedMessages.filterIsInstance<JSONRPCNotification>()
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// Verify progress notification
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val progressNotif = notifications[0]
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assertEquals("notifications/progress", progressNotif.method)
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val progressParams = progressNotif.params as JsonObject
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assertEquals("upload-123", (progressParams["progressToken"] as JsonPrimitive).content)
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assertEquals(50, (progressParams["progress"] as JsonPrimitive).content.toInt())
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// Verify list changed notifications
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assertEquals("notifications/resources/list_changed", notifications[1].method)
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assertEquals("notifications/tools/list_changed", notifications[2].method)
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// Test 3: Send various client notifications
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val clientNotifications = listOf(
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JSONRPCNotification(
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method = "notifications/progress",
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params = buildJsonObject {
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put("progressToken", JsonPrimitive("download-456"))
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put("progress", JsonPrimitive(75))
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}
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),
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JSONRPCNotification(
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method = "notifications/cancelled",
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params = buildJsonObject {
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put("requestId", JsonPrimitive("req-789"))
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put("reason", JsonPrimitive("user_cancelled"))
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}
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),
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JSONRPCNotification(
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method = "notifications/message",
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params = buildJsonObject {
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put("level", JsonPrimitive("info"))
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put("message", JsonPrimitive("Operation completed"))
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put("data", buildJsonObject {
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put("duration", JsonPrimitive(1234))
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})
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}
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)
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)
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// Send all client notifications
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clientNotifications.forEach { notification ->
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transport.send(notification)
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}
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// Verify session ID is maintained
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assertEquals("notification-test-session", transport.sessionId)
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transport.close()
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}
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@Ignore("Engine doesn't support SSECapability: https://youtrack.jetbrains.com/issue/KTOR-8177/MockEngine-Add-SSE-support")
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@Test
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fun testNotificationWithResumptionToken() = runTest {
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var resumptionTokenReceived: String? = null
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var lastEventIdSent: String? = null
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val transport = createTransport { request ->
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// Capture Last-Event-ID header
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lastEventIdSent = request.headers["Last-Event-ID"]
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when (request.method) {
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HttpMethod.Get -> {
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val sseContent = buildString {
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appendLine("event: message")
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appendLine("id: resume-100")
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appendLine("""data: {"jsonrpc":"2.0","method":"notifications/resumed","params":{"fromToken":"${lastEventIdSent}"}}""")
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appendLine()
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}
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respond(
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content = ByteReadChannel(sseContent),
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status = HttpStatusCode.OK,
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headers = headersOf(
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HttpHeaders.ContentType, ContentType.Text.EventStream.toString()
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)
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)
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}
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else -> respond("", HttpStatusCode.Accepted)
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}
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}
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transport.start()
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// Send notification with resumption token
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transport.send(
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message = JSONRPCNotification(
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method = "notifications/test",
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params = buildJsonObject {
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put("data", JsonPrimitive("test-data"))
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}
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),
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resumptionToken = "previous-token-99",
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onResumptionToken = { token ->
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resumptionTokenReceived = token
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}
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)
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// Wait for response
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delay(1.seconds)
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// Verify resumption token was sent in header
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assertEquals("previous-token-99", lastEventIdSent)
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// Verify new resumption token was received
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assertEquals("resume-100", resumptionTokenReceived)
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transport.close()
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}
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}
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