Using repetition operator + in imported grammars raises KeyError

[igordejanovic]

• parglare version: latest
• Python version: 3.6.x/3.7.x (possibly others)

Description

If + is used on the rule RHS in the imported grammar under some still uninvestigated circumstances KeyError is raised in the first sets calculation. It seems that dynamically produced symbol with _1 suffix is not unique.

Relevant part of the stacktrace:

/home/igor/repos/parglare/parglare/glr.py:72: in __init__
    force_load_table=force_load_table, table=table, **kwargs)
/home/igor/repos/parglare/parglare/parser.py:101: in __init__
    in_layout=self.in_layout)
/home/igor/repos/parglare/parglare/tables/__init__.py:88: in create_load_table
    **kwargs)
/home/igor/repos/parglare/parglare/tables/__init__.py:116: in create_table
    first_sets = first(grammar)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

grammar = <parglare.grammar.Grammar object at 0x7ff97b4e3470>

    def first(grammar):
        """Calculates the sets of terminals that can start the sentence derived from
        all grammar symbols.
    
        The Dragon book p. 221.
    
        Returns:
        dict of sets of Terminal keyed by GrammarSymbol.
        """
        assert isinstance(grammar, Grammar), \
            "grammar parameter should be Grammar instance."
    
        first_sets = {}
        for t in grammar.terminals.values():
            first_sets[t] = set([t])
        for nt in grammar.nonterminals.values():
            first_sets[nt] = set()
    
        additions = True
        while additions:
            additions = False
    
            for p in grammar.productions:
                nonterm = p.symbol
                for rhs_symbol in p.rhs:
>                   rhs_symbol_first = set(first_sets[rhs_symbol])
E                   KeyError: NonTerminal(c.unnumbered_paragraph_1)

/home/igor/repos/parglare/parglare/tables/__init__.py:748: KeyError