Implemented support for MessageSet.
diff --git a/upb/json_encode.c b/upb/json_encode.c
index bdcc976..6ec9c84 100644
--- a/upb/json_encode.c
+++ b/upb/json_encode.c
@@ -673,6 +673,9 @@
jsonenc_putsep(e, ",", first);
if (upb_fielddef_isextension(f)) {
+ // TODO: For MessageSet, I would have expected this to print the message
+ // name here, but Python doesn't appear to do this. We should do more
+ // research here about what various implementations do.
jsonenc_printf(e, "\"[%s]\":", upb_fielddef_fullname(f));
} else {
if (e->options & UPB_JSONENC_PROTONAMES) {
