Automatically produce detailed logs when failed to decode JceStructs, if 'mirai.jce.deserializer.debug' is set to `true`, helps #1899

mirai-core/src/commonMain/kotlin/utils/io/serialization/tars/Tars.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2021 Mamoe Technologies and contributors.
+ * Copyright 2019-2022 Mamoe Technologies and contributors.
  *
  * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
  * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
@@ -17,6 +17,7 @@ import kotlinx.io.core.*
 import kotlinx.serialization.*
 import kotlinx.serialization.modules.EmptySerializersModule
 import kotlinx.serialization.modules.SerializersModule
+import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLogger
 import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.TarsDecoder
 import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.TarsInput
 import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.TarsOld
@@ -38,8 +39,9 @@ internal class Tars(
         }
     }
 
-    fun <T> load(deserializer: DeserializationStrategy<T>, input: Input): T {
-        return TarsDecoder(TarsInput(input, charset), serializersModule).decodeSerializableValue(deserializer)
+    fun <T> load(deserializer: DeserializationStrategy<T>, input: Input, debugLogger: DebugLogger? = null): T {
+        val l = debugLogger ?: DebugLogger(null)
+        return TarsDecoder(TarsInput(input, charset, l), serializersModule, l).decodeSerializableValue(deserializer)
     }
 
     override fun <T> encodeToByteArray(serializer: SerializationStrategy<T>, value: T): ByteArray {
@@ -48,7 +50,7 @@ internal class Tars(
 
     override fun <T> decodeFromByteArray(deserializer: DeserializationStrategy<T>, bytes: ByteArray): T {
         bytes.read {
-            return load(deserializer, this)
+            return load(deserializer, this, null)
         }
     }
 

mirai-core/src/commonMain/kotlin/utils/io/serialization/tars/internal/TarsDecoder.kt

@@ -1,10 +1,10 @@
 /*
- * Copyright 2019-2021 Mamoe Technologies and contributors.
+ * Copyright 2019-2022 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:Suppress("PrivatePropertyName")
@@ -20,18 +20,37 @@ import kotlinx.serialization.internal.TaggedDecoder
 import kotlinx.serialization.modules.SerializersModule
 import net.mamoe.mirai.internal.utils.io.serialization.tars.Tars
 import net.mamoe.mirai.internal.utils.io.serialization.tars.TarsId
+import net.mamoe.mirai.utils.MiraiLogger
+import java.io.PrintStream
 
+internal class DebugLogger(
+    val out: PrintStream?
+) {
+    var structureHierarchy: Int = 0
+
+    fun println(message: Any?) {
+        out?.println("    ".repeat(structureHierarchy) + message)
+    }
+
+    fun println() {
+        out?.println()
+    }
+
+    inline fun println(lazyMessage: () -> String) {
+        out?.println("    ".repeat(structureHierarchy) + lazyMessage())
+    }
+}
 
 @OptIn(InternalSerializationApi::class, ExperimentalSerializationApi::class)
 internal class TarsDecoder(
-    val input: TarsInput, override val serializersModule: SerializersModule,
+    val input: TarsInput, override val serializersModule: SerializersModule, val debugLogger: DebugLogger
 ) : TaggedDecoder<TarsTag>() {
     override fun SerialDescriptor.getTag(index: Int): TarsTag {
         val annotations = this.getElementAnnotations(index)
 
         val id = annotations.filterIsInstance<TarsId>().single().id
         // ?: error("cannot find @TarsId or @ProtoNumber for ${this.getElementName(index)} in ${this.serialName}")
-        //println("getTag: ${this.getElementName(index)}=$id")
+        //debugLogger.println("getTag: ${this.getElementName(index)}=$id")
 
         return TarsTagCommon(id)
     }
@@ -79,7 +98,7 @@ internal class TarsDecoder(
         override fun decodeCollectionSize(descriptor: SerialDescriptor): Int {
             // 不要读下一个 head
             return input.currentHead.let { input.readTarsIntValue(it) }.also {
-                println { "SimpleByteArrayReader.decodeCollectionSize: $it" }
+                debugLogger.println { "SimpleByteArrayReader.decodeCollectionSize: $it" }
             }
         }
     }
@@ -114,7 +133,7 @@ internal class TarsDecoder(
         override fun decodeString(): String = input.useHead { input.readTarsStringValue(it) }
 
         override fun decodeCollectionSize(descriptor: SerialDescriptor): Int {
-            //println("decodeCollectionSize: ${descriptor.serialName}")
+            //debugLogger.println("decodeCollectionSize: ${descriptor.serialName}")
             // 不读下一个 head
             return input.useHead { input.readTarsIntValue(it) }
         }
@@ -131,19 +150,19 @@ internal class TarsDecoder(
         override fun decodeElementIndex(descriptor: SerialDescriptor): Int = error("stub")
 
         override fun endStructure(descriptor: SerialDescriptor) {
-            println { "MapReader.endStructure: ${input.currentHeadOrNull}" }
+            debugLogger.println { "MapReader.endStructure: ${input.currentHeadOrNull}" }
             [email protected](descriptor)
         }
 
         override fun beginStructure(descriptor: SerialDescriptor): CompositeDecoder {
-            println { "MapReader.beginStructure: ${input.currentHead}" }
+            debugLogger.println { "MapReader.beginStructure: ${input.currentHead}" }
             [email protected](
                 when (input.currentHead.tag) {
                     0 -> TarsTagMapEntryKey()
                     1 -> TarsTagMapEntryValue()
                     else -> error("illegal map entry head: ${input.currentHead.tag}")
                 }.also {
-                    println("MapReader.pushTag $it")
+                    debugLogger.println("MapReader.pushTag $it")
                 }
             )
             return [email protected](descriptor)
@@ -161,16 +180,16 @@ internal class TarsDecoder(
         override fun decodeEnum(enumDescriptor: SerialDescriptor): Int = decodeInt()
         override fun decodeString(): String = input.useHead { head ->
             input.readTarsStringValue(head).also {
-                println { "MapReader.decodeString: $it" }
+                debugLogger.println { "MapReader.decodeString: $it" }
             }
         }
 
         override fun decodeCollectionSize(descriptor: SerialDescriptor): Int {
-            println { "decodeCollectionSize in MapReader: ${descriptor.serialName}" }
+            debugLogger.println { "decodeCollectionSize in MapReader: ${descriptor.serialName}" }
             // 不读下一个 head
             return input.useHead { head ->
                 input.readTarsIntValue(head).also {
-                    println { "decodeCollectionSize = $it" }
+                    debugLogger.println { "decodeCollectionSize = $it" }
                 }
             }
         }
@@ -178,10 +197,10 @@ internal class TarsDecoder(
 
 
     override fun endStructure(descriptor: SerialDescriptor) {
-        structureHierarchy--
-        println { "endStructure: ${descriptor.serialName}, $currentTagOrNull, ${input.currentHeadOrNull}" }
+        debugLogger.structureHierarchy--
+        debugLogger.println { "endStructure: ${descriptor.serialName}, $currentTagOrNull, ${input.currentHeadOrNull}" }
         if (currentTagOrNull?.isSimpleByteArray == true) {
-            println { "endStructure: prepareNextHead() called" }
+            debugLogger.println { "endStructure: prepareNextHead() called" }
             currentTag.isSimpleByteArray = false
             input.prepareNextHead() // read to next head
         }
@@ -193,10 +212,10 @@ internal class TarsDecoder(
                 val currentHead = input.currentHeadOrNull ?: return
                 if (currentHead.type == Tars.STRUCT_END) {
                     input.prepareNextHead()
-                    //println("current end")
+                    //debugLogger.println("current end")
                     break
                 }
-                //println("current $currentHead")
+                //debugLogger.println("current $currentHead")
                 input.skipField(currentHead.type)
                 input.prepareNextHead()
             }
@@ -208,48 +227,32 @@ internal class TarsDecoder(
 
 
     companion object {
-        @Suppress("MemberVisibilityCanBePrivate")
-        var debuggingMode: Boolean = false
-
-        var structureHierarchy: Int = 0
-
-        inline fun println(value: () -> String) {
-            if (debuggingMode) {
-                kotlin.io.println("    ".repeat(structureHierarchy) + value())
-            }
-        }
-
-        @Suppress("NOTHING_TO_INLINE")
-        inline fun println(value: Any? = "") {
-            if (debuggingMode) {
-                kotlin.io.println("    ".repeat(structureHierarchy) + value)
-            }
-        }
+        val logger = MiraiLogger.Factory.create(TarsDecoder::class, "TarsDecoder")
     }
 
     override fun beginStructure(descriptor: SerialDescriptor): CompositeDecoder {
-        println()
-        println { "beginStructure: ${descriptor.serialName}, ${descriptor.kind}" }
-        structureHierarchy++
+        debugLogger.println()
+        debugLogger.println { "beginStructure: ${descriptor.serialName}, ${descriptor.kind}" }
+        debugLogger.structureHierarchy++
         return when (descriptor.kind) {
             is PrimitiveKind -> this@TarsDecoder
 
             StructureKind.MAP -> {
                 val tag = popTag()
-                // println("!! MAP, tag=$tag")
+                // debugLogger.println("!! MAP, tag=$tag")
                 return input.skipToHeadAndUseIfPossibleOrFail(tag.id) {
                     it.checkType(Tars.MAP, "beginStructure", tag, descriptor)
                     MapReader
                 }
             }
             StructureKind.LIST -> {
-                //println("!! ByteArray")
-                //println("decoderTag: $currentTagOrNull")
-                //println("TarsHead: " + Tars.currentHeadOrNull)
+                //debugLogger.println("!! ByteArray")
+                //debugLogger.println("decoderTag: $currentTagOrNull")
+                //debugLogger.println("TarsHead: " + Tars.currentHeadOrNull)
                 return input.skipToHeadAndUseIfPossibleOrFail(currentTag.id) {
                     // don't check type. it's polymorphic
 
-                    //println("listHead: $it")
+                    //debugLogger.println("listHead: $it")
                     when (it.type) {
                         Tars.SIMPLE_LIST -> {
                             currentTag.isSimpleByteArray = true
@@ -264,9 +267,9 @@ internal class TarsDecoder(
             StructureKind.CLASS -> {
                 currentTagOrNull ?: return this@TarsDecoder // outermost
 
-                //println("!! CLASS")
-                //println("decoderTag: $currentTag")
-                //println("TarsHead: " + Tars.currentHeadOrNull)
+                //debugLogger.println("!! CLASS")
+                //debugLogger.println("decoderTag: $currentTag")
+                //debugLogger.println("TarsHead: " + Tars.currentHeadOrNull)
                 val tag = popTag()
                 return input.skipToHeadAndUseIfPossibleOrFail(tag.id) { TarsHead ->
                     TarsHead.checkType(Tars.STRUCT_BEGIN, "beginStructure", tag, descriptor)
@@ -288,21 +291,21 @@ internal class TarsDecoder(
     override fun decodeSequentially(): Boolean = false
     override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
         var tarsHead = input.currentHeadOrNull ?: kotlin.run {
-            println("decodeElementIndex: currentHead == null")
+            debugLogger.println("decodeElementIndex: currentHead == null")
             return CompositeDecoder.DECODE_DONE
         }
 
-        println { "decodeElementIndex: ${input.currentHead}" }
+        debugLogger.println { "decodeElementIndex: ${input.currentHead}" }
         while (!input.input.endOfInput) {
             if (tarsHead.type == Tars.STRUCT_END) {
-                println { "decodeElementIndex: ${input.currentHead}" }
+                debugLogger.println { "decodeElementIndex: ${input.currentHead}" }
                 return CompositeDecoder.DECODE_DONE
             }
 
             repeat(descriptor.elementsCount) {
                 val tag = descriptor.getTarsTagId(it)
                 if (tag == tarsHead.tag) {
-                    println {
+                    debugLogger.println {
                         "name=" + descriptor.getElementName(
                             it
                         )
@@ -313,11 +316,11 @@ internal class TarsDecoder(
 
             input.skipField(tarsHead.type)
             if (!input.prepareNextHead()) {
-                println { "decodeElementIndex EOF" }
+                debugLogger.println { "decodeElementIndex EOF" }
                 break
             }
             tarsHead = input.currentHead
-            println { "next! $tarsHead" }
+            debugLogger.println { "next! $tarsHead" }
         }
 
         return CompositeDecoder.DECODE_DONE // optional support

mirai-core/src/commonMain/kotlin/utils/io/serialization/tars/internal/TarsInput.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2021 Mamoe Technologies and contributors.
+ * Copyright 2019-2022 Mamoe Technologies and contributors.
  *
  * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
  * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
@@ -12,14 +12,13 @@ package net.mamoe.mirai.internal.utils.io.serialization.tars.internal
 import kotlinx.io.charsets.Charset
 import kotlinx.io.core.*
 import net.mamoe.mirai.internal.utils.io.serialization.tars.Tars
-import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.TarsDecoder.Companion.println
 
 
 /**
  * Tars Input. 需要手动管理 head.
  */
 internal class TarsInput(
-    val input: Input, private val charset: Charset,
+    val input: Input, private val charset: Charset, private val debugLogger: DebugLogger,
 ) {
     private var _head: TarsHead? = null
     private var _nextHead: TarsHead? = null
@@ -114,7 +113,7 @@ internal class TarsInput(
         crossinline message: () -> String = { "tag not found: $tag" },
         crossinline block: (TarsHead) -> R,
     ): R {
-        return checkNotNull<R>(skipToHeadAndUseIfPossibleOrNull(tag, block), message)
+        return checkNotNull(skipToHeadAndUseIfPossibleOrNull(tag, block), message)
     }
 
     @Suppress("MemberVisibilityCanBePrivate")
@@ -170,30 +169,30 @@ internal class TarsInput(
             Tars.STRING1 -> this.input.discardExact(this.input.readUByte().toInt())
             Tars.STRING4 -> this.input.discardExact(this.input.readInt())
             Tars.MAP -> { // map
-                TarsDecoder.structureHierarchy++
+                debugLogger.structureHierarchy++
                 repeat(readInt32(0).also {
                     println("SIZE = $it")
                 } * 2) {
                     skipField(nextHead().type)
                 }
-                TarsDecoder.structureHierarchy--
+                debugLogger.structureHierarchy--
             }
             Tars.LIST -> { // list
-                TarsDecoder.structureHierarchy++
+                debugLogger.structureHierarchy++
                 repeat(readInt32(0).also {
                     println("SIZE = $it")
                 }) {
                     skipField(nextHead().type)
                 }
-                TarsDecoder.structureHierarchy--
+                debugLogger.structureHierarchy--
             }
             Tars.STRUCT_BEGIN -> {
-                TarsDecoder.structureHierarchy++
+                debugLogger.structureHierarchy++
                 var head: TarsHead
                 do {
                     head = nextHead()
                     if (head.type == Tars.STRUCT_END) {
-                        TarsDecoder.structureHierarchy--
+                        debugLogger.structureHierarchy--
                         skipField(head.type)
                         break
                     }
@@ -203,7 +202,7 @@ internal class TarsInput(
             Tars.STRUCT_END, Tars.ZERO_TYPE -> {
             }
             Tars.SIMPLE_LIST -> {
-                TarsDecoder.structureHierarchy++
+                debugLogger.structureHierarchy++
                 var head = nextHead()
                 check(head.type == Tars.BYTE) { "bad simple list element type: " + head.type + ", $head" }
                 check(head.tag == 0) { "simple list element tag must be 0, but was ${head.tag}" }
@@ -211,7 +210,7 @@ internal class TarsInput(
                 head = nextHead()
                 check(head.tag == 0) { "tag for size for simple list must be 0, but was ${head.tag}" }
                 this.input.discardExact(readTarsIntValue(head))
-                TarsDecoder.structureHierarchy--
+                debugLogger.structureHierarchy--
             }
             else -> error("invalid type: $type")
         }

mirai-core/src/commonMain/kotlin/utils/io/serialization/utils.kt

@@ -1,10 +1,10 @@
 /*
- * Copyright 2019-2021 Mamoe Technologies and contributors.
+ * Copyright 2019-2022 Mamoe Technologies and contributors.
  *
- *  此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- *  Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- *  https://github.com/mamoe/mirai/blob/master/LICENSE
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
  */
 
 @file:JvmName("SerializationUtils")
@@ -14,9 +14,11 @@
 package net.mamoe.mirai.internal.utils.io.serialization
 
 import kotlinx.io.core.*
+import kotlinx.io.streams.asInput
 import kotlinx.serialization.DeserializationStrategy
 import kotlinx.serialization.SerializationStrategy
 import kotlinx.serialization.descriptors.SerialDescriptor
+import net.mamoe.mirai.internal.message.contextualBugReportException
 import net.mamoe.mirai.internal.network.protocol.data.jce.RequestDataVersion2
 import net.mamoe.mirai.internal.network.protocol.data.jce.RequestDataVersion3
 import net.mamoe.mirai.internal.network.protocol.data.jce.RequestPacket
@@ -24,9 +26,12 @@ import net.mamoe.mirai.internal.network.protocol.data.proto.OidbSso
 import net.mamoe.mirai.internal.utils.io.JceStruct
 import net.mamoe.mirai.internal.utils.io.ProtoBuf
 import net.mamoe.mirai.internal.utils.io.serialization.tars.Tars
+import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLogger
+import net.mamoe.mirai.internal.utils.io.serialization.tars.internal.TarsDecoder
 import net.mamoe.mirai.internal.utils.printStructure
-import net.mamoe.mirai.utils.read
-import net.mamoe.mirai.utils.readPacketExact
+import net.mamoe.mirai.utils.*
+import java.io.ByteArrayOutputStream
+import java.io.PrintStream
 import kotlin.contracts.InvocationKind
 import kotlin.contracts.contract
 
@@ -39,7 +44,7 @@ internal fun <T : JceStruct> ByteArray.loadWithUniPacket(
 
 internal fun <T : JceStruct> ByteArray.loadAs(
     deserializer: DeserializationStrategy<T>,
-): T = this.read { Tars.UTF_8.load(deserializer, this) }
+): T = this.read { readJceStruct(deserializer) }
 
 internal fun <T : JceStruct> BytePacketBuilder.writeJceStruct(
     serializer: SerializationStrategy<T>,
@@ -52,11 +57,58 @@ internal fun <T : JceStruct> ByteReadPacket.readJceStruct(
     serializer: DeserializationStrategy<T>,
     length: Int = this.remaining.toInt(),
 ): T {
-    this.readPacketExact(length).use {
-        return Tars.UTF_8.load(serializer, it)
+    if (JCE_DESERIALIZER_DEBUG) {
+        // since 2.11
+        this.useBytes(n = length) { data, arrayLength ->
+            try {
+                return data.inputStream(offset = 0, length = arrayLength).asInput().use { input ->
+                    Tars.UTF_8.load(serializer, input)
+                }
+            } catch (originalException: Exception) {
+                val log = ByteArrayOutputStream()
+                try {
+                    val value = PrintStream(log).use { stream ->
+                        stream.println("\nData: ")
+                        stream.println(data.toUHexString(length = arrayLength))
+                        stream.println("Trace:")
+
+                        data.inputStream(offset = 0, length = arrayLength).asInput().use { input ->
+                            Tars.UTF_8.load(serializer, input, debugLogger = DebugLogger(stream))
+                        }
+                    }
+                    return value.also {
+                        TarsDecoder.logger.warning(
+                            contextualBugReportException(
+                                "解析 " + serializer.descriptor.serialName,
+                                "启用 debug 模式后解析正常: $value \n\n${log.toByteArray().decodeToString()}",
+                                originalException
+                            )
+                        )
+                    }
+                } catch (secondFailure: Exception) {
+                    throw contextualBugReportException(
+                        "解析 " + serializer.descriptor.serialName,
+                        log.toByteArray().decodeToString(),
+                        ExceptionCollector.compressExceptions(originalException, secondFailure)
+                    )
+                }
+            }
+        }
+    } else {
+        // since 2.0
+        return this.readPacketExact(length).use {
+            Tars.UTF_8.load(serializer, it)
+        }
     }
 }
 
+/**
+ * @since 2.11
+ */
+internal var JCE_DESERIALIZER_DEBUG by lateinitMutableProperty {
+    systemProp("mirai.jce.deserializer.debug", false)
+}
+
 internal fun <T : JceStruct> BytePacketBuilder.writeJceRequestPacket(
     version: Int = 3,
     servantName: String,

mirai-core/src/commonTest/kotlin/utils/io/serialization/tars/internal/DebugLoggerTest.kt

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2019-2022 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
+ */
+
+package net.mamoe.mirai.internal.utils.io.serialization.tars.internal
+
+import kotlinx.serialization.Serializable
+import net.mamoe.mirai.internal.test.AbstractTest
+import net.mamoe.mirai.internal.utils.io.JceStruct
+import net.mamoe.mirai.internal.utils.io.serialization.JCE_DESERIALIZER_DEBUG
+import net.mamoe.mirai.internal.utils.io.serialization.readJceStruct
+import net.mamoe.mirai.internal.utils.io.serialization.tars.Tars
+import net.mamoe.mirai.internal.utils.io.serialization.tars.TarsId
+import net.mamoe.mirai.internal.utils.io.serialization.toByteArray
+import net.mamoe.mirai.utils.toReadPacket
+import net.mamoe.mirai.utils.toUHexString
+import org.junit.jupiter.api.Test
+import java.io.ByteArrayOutputStream
+import java.io.PrintStream
+import kotlin.test.assertEquals
+import kotlin.test.assertFails
+
+class DebugLoggerTest : AbstractTest() {
+    init {
+        JCE_DESERIALIZER_DEBUG = true
+    }
+
+    @Serializable
+    data class Struct(
+        @TarsId(1) val str: String,
+        @TarsId(2) val int: Int,
+    ) : JceStruct
+
+    @Test
+    fun `can log`() {
+        val out = ByteArrayOutputStream()
+        val logger = DebugLogger(PrintStream(out))
+        val original = Struct("string", 1)
+        val bytes = original.toByteArray(Struct.serializer())
+        val value = bytes.toReadPacket().use { Tars.UTF_8.load(Struct.serializer(), it, logger) }
+        assertEquals(original, value)
+        assertEquals(
+            """
+            beginStructure: net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLoggerTest.Struct, CLASS
+                decodeElementIndex: TarsHead(tag=1, type=6(String1))
+                name=str
+                decodeElementIndex: TarsHead(tag=2, type=0(Byte))
+                name=int
+                decodeElementIndex: currentHead == null
+            endStructure: net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLoggerTest.Struct, null, null
+        """.trimIndent(), out.toByteArray().decodeToString().trim()
+        )
+    }
+
+    @Test
+    fun `can auto log`() {
+        val original = Struct("string", 1)
+        val bytes = original.toByteArray(Struct.serializer())
+        println(bytes.toUHexString()) // 16 06 73 74 72 69 6E 67 20 01
+        bytes[bytes.lastIndex - 1] = 0x30.toByte() // change tag
+        val exception = assertFails { bytes.toReadPacket().use { it.readJceStruct(Struct.serializer()) } }
+        assertEquals(
+            """
+            在 解析 net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLoggerTest.Struct 时遇到了意料之中的问题. 请完整复制此日志提交给 mirai: https://github.com/mamoe/mirai/issues/new/choose    调试信息: 
+            Data: 
+            16 06 73 74 72 69 6E 67 30 01
+            Trace:
+            
+            beginStructure: net.mamoe.mirai.internal.utils.io.serialization.tars.internal.DebugLoggerTest.Struct, CLASS
+                decodeElementIndex: TarsHead(tag=1, type=6(String1))
+                name=str
+                decodeElementIndex: TarsHead(tag=3, type=0(Byte))
+        """.trimIndent(), exception.message!!.trim()
+        )
+    }
+}