Report position in source sequence on ParseError

[Cory Dodt]

This fairly simple change is enormously helpful to me in debugging my grammars. I would like something like this in the standard apply implementation:

        try:
            return self.apply(rule)
        except ParseError:
            if DEBUG: # pragma: nocover
                _debugShow(self)
            raise

def _debugShow(parser):
    """
    Show where parsing failed
    """
    pos = parser.input.position
    data = parser.input.data
    left, right = map(''.join, [data[:pos], data[pos:]])
    lineno = left.count('\n')
    print lineno,
    if len(left) > 20:
        print repr('...' + left[-20:]),
    print '!!',
    if len(right) > 20:
        print repr(right[:20] + '...')

Of course this would have to be somewhat modified to handle non-string sequences.

[Allen Short (washort)]

I think ParseError.formatError addresses this now.