gitmirror/tests/test_grammar.py

from __future__ import absolute_import

import sys
from unittest import TestCase, main

from lark import Lark, Token, Tree
from lark.load_grammar import GrammarLoader, GrammarError


class TestGrammar(TestCase):
    def setUp(self):
        pass

    def test_errors(self):
        for msg, examples in GrammarLoader.ERRORS:
            for example in examples:
                try:
                    p = Lark(example)
                except GrammarError as e:
                    assert msg in str(e)
                else:
                    assert False, "example did not raise an error"

    def test_override_rule(self):
        # Overrides the 'sep' template in existing grammar to add an optional terminating delimiter
        # Thus extending it beyond its original capacity
        p = Lark("""
            %import .test_templates_import (start, sep)

            %override sep{item, delim}: item (delim item)* delim?
            %ignore " "
        """, source_path=__file__)

        a = p.parse('[1, 2, 3]')
        b = p.parse('[1, 2, 3, ]')
        assert a == b

    def test_override_terminal(self):
        p = Lark("""
            
            %import .grammars.ab (startab, A, B)
            
            %override A: "c"
            %override B: "d"
        """, start='startab', source_path=__file__)

        a = p.parse('cd')
        self.assertEqual(a.children[0].children, [Token('A', 'c'), Token('B', 'd')])

    def test_extend_rule(self):
        p = Lark("""
            %import .grammars.ab (startab, A, B, expr)

            %extend expr: B A
        """, start='startab', source_path=__file__)
        a = p.parse('abab')
        self.assertEqual(a.children[0].children, ['a', Tree('expr', ['b', 'a']), 'b'])

    def test_extend_term(self):
        p = Lark("""
            %import .grammars.ab (startab, A, B, expr)
            
            %extend A: "c"
        """, start='startab', source_path=__file__)
        a = p.parse('acbb')
        self.assertEqual(a.children[0].children, ['a', Tree('expr', ['c', 'b']), 'b'])



if __name__ == '__main__':
    main()