[lldb] Fix incorrect error handling in GDBRemoteCommunicationClient::SendGetSupportedTraceType

[teemperor]

Summary

GDBRemoteCommunicationClient::SendGetSupportedTraceType is checking whether the
response is !response.IsNormalResponse() and infers from that that it is an error response.
However, it could be either "unsupported" or "error". If we get an unsupported response,
the code then tries to generate an llvm::Expected from the non-error response which then asserts.

Debugserver doesn't implement jLLDBTraceSupportedType, so we get an unsupported response
whenever this function is called on macOS.

This fixes the TestAproposWithProcess on macOS (where the apropos command will query
the CommandObjectTraceStart which then sends the trace type query package).

[shafik]

LGTM, there are no tests currently?

[wallace]

Thanks

[teemperor]

From what understand this is Linux exclusive feature at the moment, and the command test itself is testing the command but missing the edge case of testing this against a running process. Not sure if it's worth starting a process just to test that the command still just prints the "unsupported feature" error. I'll leave a dedicated test up to @wallace .

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp

GDBRemoteCommunicationClient::SendGetSupportedTraceType() {
 
   StreamGDBRemote escaped_packet;
   escaped_packet.PutCString("jLLDBTraceSupportedType");
 
   StringExtractorGDBRemote response;
   if (SendPacketAndWaitForResponse(escaped_packet.GetString(), response,
                                    true) ==
       GDBRemoteCommunication::PacketResult::Success) {
-    if (!response.IsNormalResponse())
+    if (response.IsErrorResponse())
       return response.GetStatus().ToError();
+    if (response.IsUnsupportedResponse())
+      return llvm::createStringError(llvm::inconvertibleErrorCode(),
+                                     "jLLDBTraceSupportedType is unsupported");
 
     if (llvm::Expected<TraceTypeInfo> type =
             llvm::json::parse<TraceTypeInfo>(response.Peek()))
       return *type;
     else
       return type.takeError();
   }
   LLDB_LOG(log, "failed to send packet: jLLDBTraceSupportedType");