test_direct_rule_call.py

from __future__ import unicode_literals
import pytest
from arpeggio import SemanticAction, ParserPython

def test_direct_rule_call():
    '''
    Test regression where in direct rule call semantic action is
    erroneously attached to both caller and callee.
    '''

    def grammar():  return rule1, rule2
    def rule1():    return "a"
    def rule2():    return rule1

    call_count = [0]

    class DummySemAction(SemanticAction):
        def first_pass(self, parser, node, nodes):
            call_count[0] += 1
            return SemanticAction.first_pass(self, parser, node, nodes)

    # Sem action is attached to rule2 only but
    # this bug will attach it to rule1 also resulting in
    # wrong call count.
    rule2.sem = DummySemAction()

    parser = ParserPython(grammar)
    parse_tree = parser.parse("aa")
    parser.getASG()

    assert call_count[0] == 1, "Semantic action should be called once!"