Null checks?

[nettrino]

Hello,

First of all, thanks for gramtest!I tried to run the postal.bnf (committed) and were getting NullPointerExceptions so I made these very limited changes to get through them. Since I am (very) new to ANTLR I am not sure if this is desired functionality or not. If you think this is indeed a bug feel free to merge. Also the fixes are very rough, and probably don't address the whole issue.

Also, on a separate note, I was thinking in porting gramtest to accept ANTLR grammars instead of BNF. Do you think that would be easy?

Thanks again,

Theofilos

[codelion]

Hi @nettrino

The NullPointerExceptions were due to the fact that the grammar was missing a production for <space> I think we should do more validation on the grammar and improve the error messages to avoid confusion. (There is an existing issue for that #2, PRs are welcome btw ;))

But for your test case, if you use the grammar below there won't be any exceptions:

  <postalcode>           ::= <forwardsortationarea> <space> <localdeliveryunit>
  <forwardsortationarea> ::= <provarea> <loctype> <letter>
  <localdeliveryunit>    ::= <digit> <letter> <digit>
  <provarea>             ::= A | B | C | E | G | H | J | K | L | M | N |
                             P | R | S | T | V | X | Y
  <loctype>              ::= <rural> | <urban>
  <rural>                ::= 0
  <urban>                ::= 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
  <letter>               ::= A | B | C | E | G | H | J | K | L | M | N |
                             P | R | S | T | V | W | X | Y | Z
  <digit>                ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
  <space>             ::= " "

If you notice the way Gramtest is implemented it uses an ANTLR grammar for BNF to implement the parser. I am not sure how much effort will it be to accept arbitrary ANTLR grammars themselves, we may have to hook into the generic ANTLR visitor instead of bnfBaseVisitor as done currently.

[nettrino]

That makes sense. Thanks for the prompt reply!