Invalid subdocs errors unclear

Combinations of various invalid subdocs result in really unclear error messages that don't really explain why the op failed. For instance :

List<MutateInSpec> spec = new ArrayList<>();
spec.add(MutateInSpec.upsert("xattr1", "xvalue1").xattr());
spec.add(MutateInSpec.insert("", obj));

col.mutateIn("test", spec, MutateInOptions.mutateInOptions().storeSemantics(StoreSemantics.UPSERT));

Similar can be seen by putting xattr ops as not the first operation in the list.

Results in a stack trace looking like

Exception in thread "main" com.couchbase.client.core.error.DecodingFailedException: java.lang.IndexOutOfBoundsException: Index 2 out of bounds for length 2Exception in thread "main" com.couchbase.client.core.error.DecodingFailedException: java.lang.IndexOutOfBoundsException: Index 2 out of bounds for length 2 at com.couchbase.client.java.AsyncUtils.block(AsyncUtils.java:51) at com.couchbase.client.java.Collection.mutateIn(Collection.java:480) at Thing.main(Thing.java:71) Suppressed: java.lang.Exception: The above exception was originally thrown by another thread at the following location. at com.couchbase.client.core.io.netty.kv.KeyValueMessageHandler.decode(KeyValueMessageHandler.java:289) at com.couchbase.client.core.io.netty.kv.KeyValueMessageHandler.channelRead(KeyValueMessageHandler.java:220) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.io.netty.kv.MemcacheProtocolVerificationHandler.channelRead(MemcacheProtocolVerificationHandler.java:84) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:328) at com.couchbase.client.core.deps.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:302) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.handler.flush.FlushConsolidationHandler.channelRead(FlushConsolidationHandler.java:154) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1422) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:931) at com.couchbase.client.core.deps.io.netty.channel.kqueue.AbstractKQueueStreamChannel$KQueueStreamUnsafe.readReady(AbstractKQueueStreamChannel.java:544) at com.couchbase.client.core.deps.io.netty.channel.kqueue.AbstractKQueueChannel$AbstractKQueueUnsafe.readReady(AbstractKQueueChannel.java:381) at com.couchbase.client.core.deps.io.netty.channel.kqueue.KQueueEventLoop.processReady(KQueueEventLoop.java:211) at com.couchbase.client.core.deps.io.netty.channel.kqueue.KQueueEventLoop.run(KQueueEventLoop.java:289) at com.couchbase.client.core.deps.io.netty.util.concurrent.SingleThreadEventExecutor$6.run(SingleThreadEventExecutor.java:1044) at com.couchbase.client.core.deps.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) at com.couchbase.client.core.deps.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.base/java.lang.Thread.run(Thread.java:834)Caused by: java.lang.IndexOutOfBoundsException: Index 2 out of bounds for length 2 at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64) at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70) at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248) at java.base/java.util.Objects.checkIndex(Objects.java:372) at java.base/java.util.ArrayList.get(ArrayList.java:458) at com.couchbase.client.core.msg.kv.SubdocMutateRequest.decode(SubdocMutateRequest.java:180) at com.couchbase.client.core.msg.kv.SubdocMutateRequest.decode(SubdocMutateRequest.java:43) at com.couchbase.client.core.io.netty.kv.KeyValueMessageHandler.decode(KeyValueMessageHandler.java:286) at com.couchbase.client.core.io.netty.kv.KeyValueMessageHandler.channelRead(KeyValueMessageHandler.java:220) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.io.netty.kv.MemcacheProtocolVerificationHandler.channelRead(MemcacheProtocolVerificationHandler.java:84) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:328) at com.couchbase.client.core.deps.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:302) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.handler.flush.FlushConsolidationHandler.channelRead(FlushConsolidationHandler.java:154) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352) at com.couchbase.client.core.deps.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1422) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374) at com.couchbase.client.core.deps.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360) at com.couchbase.client.core.deps.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:931) at com.couchbase.client.core.deps.io.netty.channel.kqueue.AbstractKQueueStreamChannel$KQueueStreamUnsafe.readReady(AbstractKQueueStreamChannel.java:544) at com.couchbase.client.core.deps.io.netty.channel.kqueue.AbstractKQueueChannel$AbstractKQueueUnsafe.readReady(AbstractKQueueChannel.java:381) at com.couchbase.client.core.deps.io.netty.channel.kqueue.KQueueEventLoop.processReady(KQueueEventLoop.java:211) at com.couchbase.client.core.deps.io.netty.channel.kqueue.KQueueEventLoop.run(KQueueEventLoop.java:289) at com.couchbase.client.core.deps.io.netty.util.concurrent.SingleThreadEventExecutor$6.run(SingleThreadEventExecutor.java:1044) at com.couchbase.client.core.deps.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) at com.couchbase.client.core.deps.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.base/java.lang.Thread.run(Thread.java:834)