proto: add invalid JSON to JSONBMarshalToMessage error message

This change makes debugging easier by including the invalid JSON
in that caused JSONBMarshalToMessage to fail.

Release note: None

Author: ecwall

pkg/sql/logictest/testdata/logic_test/builtin_function

@@ -2989,7 +2989,7 @@ select crdb_internal.json_to_pb('cockroach.sql.sqlbase.Descriptor', crdb_interna
 ----
 true
 
-query error pq: crdb_internal.json_to_pb\(\): invalid proto JSON: unmarshaling json to cockroach.sql.sqlbase.Descriptor: unknown field "__redacted__" in descpb.Descriptor
+query error pq: crdb_internal.json_to_pb\(\): invalid proto JSON: unmarshaling to cockroach.sql.sqlbase.Descriptor json: .+ unknown field "__redacted__" in descpb.Descriptor
 select crdb_internal.json_to_pb('cockroach.sql.sqlbase.Descriptor', crdb_internal.pb_to_json('cockroach.sql.sqlbase.Descriptor', descriptor, true, true)) = descriptor from system.descriptor where id = 1
 
 subtest regexp_split

pkg/sql/protoreflect/utils.go

@@ -123,8 +123,9 @@ func MessageToJSON(msg protoutil.Message, flags FmtFlags) (jsonb.JSON, error) {
 // Returns serialized byte representation of the protocol message.
 func JSONBMarshalToMessage(input jsonb.JSON, target protoutil.Message) ([]byte, error) {
 	json := &jsonpb.Unmarshaler{}
-	if err := json.Unmarshal(strings.NewReader(input.String()), target); err != nil {
-		return nil, errors.Wrapf(err, "unmarshaling json to %s", proto.MessageName(target))
+	jsonString := input.String()
+	if err := json.Unmarshal(strings.NewReader(jsonString), target); err != nil {
+		return nil, errors.Wrapf(err, "unmarshaling to %s json: %s", proto.MessageName(target), jsonString)
 	}
 	data, err := protoutil.Marshal(target)
 	if err != nil {