fix(rpc): assertion failure due to invalid msgpack input

Problem:
  rbuffer_consumed assertion fails if Unpacker fails to parse msgpack,
  because it doesn't consume bytes on errors

Solution:
  Call rbuffer_consumed_compact only if Unpacker isn't closed

1 files changed, 5 insertions, 2 deletions

diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index 286bb8098a..0178ef622b 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -304,8 +304,11 @@ static void receive_msgpack(Stream *stream, RBuffer *rbuf, size_t c, void *data,
   p->read_ptr = rbuffer_read_ptr(rbuf, &size);
   p->read_size = size;
   parse_msgpack(channel);
-  size_t consumed = size - p->read_size;
-  rbuffer_consumed_compact(rbuf, consumed);
+
+  if (!unpacker_closed(p)) {
+    size_t consumed = size - p->read_size;
+    rbuffer_consumed_compact(rbuf, consumed);
+  }
 
 end:
   channel_decref(channel);