Unexpected NoMatch when suppressing a StrMatch from the parse tree

[vpavlu]

Hi! I have a grammar where newlines matter but I don't want the newlines to be part of the parse tree. Tried to suppress the newlines using http://textx.github.io/Arpeggio/2.0/parse_trees/#suppressing-parse-tree-nodes but hit a wall.

Here's my reduced example:

from arpeggio import ZeroOrMore, RegExMatch, StrMatch, EOF
from arpeggio import ParserPython

class SuppressStrMatch(StrMatch):
    suppress = True


#newline = StrMatch('\n')         # with this i get a successful parse
newline = SuppressStrMatch('\n')  # with this i get a NoMatch at (3, 1)

def line():                    return RegExMatch(r'^.*$'), newline

def grammar():                 return ZeroOrMore(line), EOF



parser = ParserPython(grammar, debug=True, skipws=False)
result = parser.parse('one\n\nthree\nfour\n')
print(result.tree_str())

Running this with 'Arpeggio==2.0.0' gives me arpeggio.NoMatch: Expected EOF at position (3, 1) => 'one\n\n*three\nfour'. When I use newline = StrMatch('\n') instead of the suppressed newline = SuppressStrMatch('\n') the input is parsed with success. Seems to be a problem with suppress altering parser behaviour?

[igordejanovic]

Thanks for the report and the reduced example. I confirm that it is a bug. At first glance it seems that it is a bad interplay between the ZeroOrMore rule and suppressed match. Zero or more thinks that the suppressed rule match is not successful and tries to continue by matching EOF.