grammar test

grammar.txt

# cat file: lib/Presenters.pm6
unit module Presenters;
use Grammar::Tracer;
grammar Presenters::PGrammar {
    token TOP {
        [
            | <entry>
            | <blank>
        ]+
    }
    token entry   { <key> <sep> <value> }
    token key     { \h* \w+ }
    token sep     { \h* ':' \h* }
    token value   { \N+ }
    token blank   { \h* \n }
}

# cat file: ./test-presenters.data
id: laue-d 
name: Lauer, Denny 
id: horn-a
name: Hornstein, Anne
id: bran-e
name: Branch, Eddie

# cat file: ./grammar-test-fail.p6
#!/usr/bin/env perl6
use lib <./lib>;
use Presenters;
my $pfil  = "test-presenters.data";
my $mp = Presenters::PGrammar.parse(slurp $pfil);
say "WARNING: Presenters grammar failed to match." if !$mp;
say $mp;

# executing
./grammar-test-fail.p6
TOP
Cannot invoke this object (REPR: Null; VMNull)
  in block  at /usr/local/rakudo.d/share/perl6/site/sources/C0DCFF5AEFDF38901A375AE53AF39C4F12B3F6FC (Grammar::Tracer) line 43
  in regex TOP at /usr/local/people/tbrowde/mydata/tbrowde-home-bzr/mydomains/domains/primary-web-servers/web-sites/computertechnwf.org/public/lib/Presenters.pm6 (Presenters) line 6
  in block  at /usr/local/rakudo.d/share/perl6/site/sources/C0DCFF5AEFDF38901A375AE53AF39C4F12B3F6FC (Grammar::Tracer) line 49
  in block <unit> at ./grammar-test-fail.p6 line 7

# after removing "use Grammar::Tracer" the code runs to completion:

# executing
./grammar-test-fail.p6
｢id: laue-d
name: Lauer, Denny
id: horn-a
name: Hornstein, Anne
id: bran-e
name: Branch, Eddie
｣
 entry => ｢id: laue-d｣
  key => ｢id｣
  sep => ｢: ｣
  value => ｢laue-d｣
 blank => ｢
｣
 entry => ｢name: Lauer, Denny｣
  key => ｢name｣
  sep => ｢: ｣
  value => ｢Lauer, Denny｣
 blank => ｢
｣
 entry => ｢id: horn-a｣
  key => ｢id｣
  sep => ｢: ｣
  value => ｢horn-a｣
 blank => ｢
｣
 entry => ｢name: Hornstein, Anne｣
  key => ｢name｣
  sep => ｢: ｣
  value => ｢Hornstein, Anne｣
 blank => ｢
｣
 entry => ｢id: bran-e｣
  key => ｢id｣
  sep => ｢: ｣
  value => ｢bran-e｣
 blank => ｢
｣
 entry => ｢name: Branch, Eddie｣
  key => ｢name｣
  sep => ｢: ｣
  value => ｢Branch, Eddie｣
 blank => ｢
｣