KTOR-5479 Improve log message about skipping response body transforma… (

#3379)

* KTOR-5479 Improve log message about skipping response body transformation in the ContentNegotiation

ktor-server/ktor-server-plugins/ktor-server-content-negotiation/jvm/test/LogTest.kt

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2014-2023 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.server.plugins.contentnegotiation
+
+import ch.qos.logback.classic.*
+import ch.qos.logback.classic.spi.*
+import ch.qos.logback.core.read.ListAppender
+import io.ktor.client.request.*
+import io.ktor.server.application.*
+import io.ktor.server.response.*
+import io.ktor.server.routing.*
+import io.ktor.server.testing.*
+import kotlin.test.*
+
+class LogTest {
+    @Test
+    fun ignoredTypeMessageForResponseBody() {
+        val logger = LOGGER as Logger
+        logger.level = Level.ALL
+
+        val listAppender = ListAppender<ILoggingEvent>()
+        logger.addAppender(listAppender)
+        listAppender.start()
+
+        val plugin = createRouteScopedPlugin("PartialContentNegotiation", ::ContentNegotiationConfig) {
+            convertResponseBody()
+        }
+
+        testApplication {
+            application {
+                install(plugin)
+                routing {
+                    get("/") {
+                        call.respond("test")
+                    }
+                }
+            }
+
+            client.get("/")
+
+            listAppender.stop()
+            assertEquals(
+                "Skipping response body transformation from String to OutgoingContent for the GET / request" +
+                    " because the String type is ignored. See [ContentNegotiationConfig::ignoreType].",
+                listAppender.list[0].message
+            )
+        }
+    }
+}

ktor-server/ktor-server-plugins/ktor-server-content-negotiation/jvmAndNix/src/io/ktor/server/plugins/contentnegotiation/ResponseConverter.kt

@@ -9,6 +9,7 @@ import io.ktor.http.content.*
 import io.ktor.serialization.*
 import io.ktor.server.application.*
 import io.ktor.server.http.content.*
+import io.ktor.server.request.*
 import io.ktor.server.response.*
 import io.ktor.utils.io.charsets.*
 
@@ -21,7 +22,13 @@ internal fun PluginBuilder<ContentNegotiationConfig>.convertResponseBody() = onC
     }
 
     if (pluginConfig.ignoredTypes.any { it.isInstance(subject) }) {
-        LOGGER.trace("Skipping because the type is ignored.")
+        val sourceClass = subject::class.simpleName
+        val requestInfo = "${call.request.httpMethod.value} ${call.request.uri}"
+
+        LOGGER.trace(
+            "Skipping response body transformation from $sourceClass to OutgoingContent for the $requestInfo request" +
+            " because the $sourceClass type is ignored. See [ContentNegotiationConfig::ignoreType]."
+        )
         return@onCallRespond
     }