Support message with no fields

[pma]

The grammar won't accept a message with no fields. Example (see Derived2):

message Base {
  enum MsgType {
    Derived1 = 1;
    Derived2 = 2;
  }

  message Derived1 {
    required uint32 extra1 = 1;
  }

  message Derived2 {
  }

  required MsgType type = 1;
  optional Derived1 derived1 = 2;
  optional Derived2 derived2 = 3;
}

Tried with other libs including gpb (erlang), protoc (python), protobuf-j2me (java) and they manage to parse it.

[jeremyong]

Mind posting the error?

[pma]

iex(1)> tokens = Exprotoc.Parser.tokenize("base.proto", ["priv"])
iex(2)> Exprotoc.Parser.parse(tokens)
** (MatchError) no match of right hand side value: {:error, {12, :proto_grammar, ['syntax error before: ', '\'}\'']}}
     lib/exprotoc/parser.ex:36: Exprotoc.Parser.parse/1

The yecc generated parser is returning an error on line 12 of the base.proto, which is the unexpected '}'.

The yrl file defines a message as:

p_message -> message message_name '{' fields '}' : {message, '$2', '$4'}.

and fields can't be empty.

[jeremyong]

Gotcha this should be pretty easy to fix. I'll try to get to it later today.