KTOR-9125 Fix double ResponseSent invocation when exception is thrown after respond (#5215)

Author: marychatte

ktor-server/ktor-server-core/common/src/io/ktor/server/engine/DefaultEnginePipeline.kt

@@ -11,13 +11,13 @@ import io.ktor.server.engine.internal.*
 import io.ktor.server.logging.*
 import io.ktor.server.plugins.*
 import io.ktor.server.response.*
-import io.ktor.server.routing.routingCallKey
+import io.ktor.server.routing.*
 import io.ktor.util.cio.*
 import io.ktor.util.logging.*
 import io.ktor.util.pipeline.*
 import io.ktor.utils.io.*
-import kotlinx.coroutines.*
 import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.TimeoutCancellationException
 import kotlinx.io.IOException
 
 /**
@@ -62,6 +62,8 @@ public fun defaultEnginePipeline(config: ApplicationConfig, developmentMode: Boo
  */
 public suspend fun handleFailure(call: ApplicationCall, error: Throwable) {
     logError(call, error)
+    if (call.response.isSent) return
+
     tryRespondError(call, defaultExceptionStatusCode(error) ?: HttpStatusCode.InternalServerError)
 }
 

ktor-server/ktor-server-test-host/common/src/io/ktor/server/testing/TestApplicationEngine.kt

@@ -121,6 +121,7 @@ public class TestApplicationEngine(
 
     private suspend fun handleTestFailure(call: ApplicationCall, cause: Throwable) {
         logError(call, cause)
+        if (call.response.isSent) return
 
         val throwOnException = environment.config
             .propertyOrNull(CONFIG_KEY_THROW_ON_EXCEPTION)

ktor-server/ktor-server-test-suites/common/src/io/ktor/server/testing/suites/HttpServerCommonTestSuite.kt

@@ -795,6 +795,36 @@ abstract class HttpServerCommonTestSuite<TEngine : ApplicationEngine, TConfigura
         }
     }
 
+    @Test
+    fun testResponseSentCalledOnce() = runTest {
+        var responseSentCalled = 0
+        createAndStartServer {
+            serverConfig {
+                enableSsl = false
+                enableHttp2 = false
+            }
+            install(
+                createRouteScopedPlugin("Plugin") {
+                    on(ResponseSent) {
+                        responseSentCalled++
+                    }
+                }
+            )
+
+            get("/") {
+                call.respond("ok")
+                throw ExpectedTestException("exception")
+            }
+        }
+
+        withUrl("/") {
+            assertEquals(HttpStatusCode.OK, status)
+            assertEquals("ok", bodyAsText())
+        }
+        delay(500)
+        assertEquals(1, responseSentCalled)
+    }
+
     private data class TestData(
         val name: String
     ) : AbstractCoroutineContextElement(TestData) {