Grammar sends Earley implementation to an infinite loop about lark HOT 5 CLOSED

Fixed!

from lark.

@erezsh If I understand correctly, this grammar is not malformed, but also enters into an infinite loop:

from lark import Lark

l = Lark('''
  start: bar+
  bar: /a|b|c*/ "foo"
''')

l.parse('afoobfooccfoo')

from lark.

It seems the issue is that the regex can match zero characters. This one works fine:

Lark('''
  start: bar+
  bar: /a|b|c+/ "foo"
''')

and this one fails in the same way as the example above:

Lark('''
  start: bar+
  bar: /a|b|/ "foo"
''')

from lark.

Thanks, good catch!

I think the correct response is to forbid empty regexps.

from lark.

Both issues resolved.

from lark.