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from __future__ import absolute_import
import os
from unittest import TestCase, main
from lark import Lark, Token, Tree, ParseError, UnexpectedInput
from lark.load_grammar import GrammarError, GRAMMAR_ERRORS, find_grammar_errors, list_grammar_imports
from lark.load_grammar import FromPackageLoader
class TestGrammar(TestCase):
def setUp(self):
pass
def test_errors(self):
for msg, examples in GRAMMAR_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_empty_literal(self):
# Issues #888
self.assertRaises(GrammarError, Lark, "start: \"\"")
def test_ignore_name(self):
spaces = []
p = Lark("""
start: "a" "b"
WS: " "
%ignore WS
""", parser='lalr', lexer_callbacks={'WS': spaces.append})
assert p.parse("a b") == p.parse("a b")
assert len(spaces) == 5
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
self.assertRaises(GrammarError, Lark, """
%import .test_templates_import (start, sep)
%override sep{item}: item (delim item)* delim?
""", source_path=__file__)
self.assertRaises(GrammarError, Lark, """
%override sep{item}: item (delim item)* delim?
""", source_path=__file__)
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'])
self.assertRaises(GrammarError, Lark, """
%extend expr: B A
""")
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'])
def test_extend_twice(self):
p = Lark("""
start: x+
x: "a"
%extend x: "b"
%extend x: "c"
""")
assert p.parse("abccbba") == p.parse("cbabbbb")
def test_undefined_ignore(self):
g = """!start: "A"
%ignore B
"""
self.assertRaises( GrammarError, Lark, g)
g = """!start: "A"
%ignore start
"""
self.assertRaises( GrammarError, Lark, g)
def test_alias_in_terminal(self):
g = """start: TERM
TERM: "a" -> alias
"""
self.assertRaises( GrammarError, Lark, g)
def test_undefined_rule(self):
self.assertRaises(GrammarError, Lark, """start: a""")
def test_undefined_term(self):
self.assertRaises(GrammarError, Lark, """start: A""")
def test_token_multiline_only_works_with_x_flag(self):
g = r"""start: ABC
ABC: / a b c
d
e f
/i
"""
self.assertRaises( GrammarError, Lark, g)
def test_import_custom_sources(self):
custom_loader = FromPackageLoader(__name__, ('grammars', ))
grammar = """
start: startab
%import ab.startab
"""
p = Lark(grammar, import_paths=[custom_loader])
self.assertEqual(p.parse('ab'),
Tree('start', [Tree('startab', [Tree('ab__expr', [Token('ab__A', 'a'), Token('ab__B', 'b')])])]))
def test_import_custom_sources2(self):
custom_loader = FromPackageLoader(__name__, ('grammars', ))
grammar = """
start: rule_to_import
%import test_relative_import_of_nested_grammar__grammar_to_import.rule_to_import
"""
p = Lark(grammar, import_paths=[custom_loader])
x = p.parse('N')
self.assertEqual(next(x.find_data('rule_to_import')).children, ['N'])
def test_import_custom_sources3(self):
custom_loader2 = FromPackageLoader(__name__)
grammar = """
%import .test_relative_import (start, WS)
%ignore WS
"""
p = Lark(grammar, import_paths=[custom_loader2], source_path=__file__) # import relative to current file
x = p.parse('12 capybaras')
self.assertEqual(x.children, ['12', 'capybaras'])
def test_find_grammar_errors(self):
text = """
a: rule
b rule
c: rule
B.: "hello" f
D: "okay"
"""
assert [e.line for e, _s in find_grammar_errors(text)] == [3, 5]
text = """
a: rule
b rule
| ok
c: rule
B.: "hello" f
D: "okay"
"""
assert [e.line for e, _s in find_grammar_errors(text)] == [3, 4, 6]
text = """
a: rule @#$#@$@&&
b: rule
| ok
c: rule
B: "hello" f @
D: "okay"
"""
x = find_grammar_errors(text)
assert [e.line for e, _s in find_grammar_errors(text)] == [2, 6]
def test_ranged_repeat_terms(self):
g = u"""!start: AAA
AAA: "A"~3
"""
l = Lark(g, parser='lalr')
self.assertEqual(l.parse(u'AAA'), Tree('start', ["AAA"]))
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AA')
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AAAA')
g = u"""!start: AABB CC
AABB: "A"~0..2 "B"~2
CC: "C"~1..2
"""
l = Lark(g, parser='lalr')
self.assertEqual(l.parse(u'AABBCC'), Tree('start', ['AABB', 'CC']))
self.assertEqual(l.parse(u'BBC'), Tree('start', ['BB', 'C']))
self.assertEqual(l.parse(u'ABBCC'), Tree('start', ['ABB', 'CC']))
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AAAB')
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AAABBB')
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'ABB')
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AAAABB')
def test_ranged_repeat_large(self):
g = u"""!start: "A"~60
"""
l = Lark(g, parser='lalr')
self.assertGreater(len(l.rules), 1, "Expected that more than one rule will be generated")
self.assertEqual(l.parse(u'A' * 60), Tree('start', ["A"] * 60))
self.assertRaises(ParseError, l.parse, u'A' * 59)
self.assertRaises((ParseError, UnexpectedInput), l.parse, u'A' * 61)
g = u"""!start: "A"~15..100
"""
l = Lark(g, parser='lalr')
for i in range(0, 110):
if 15 <= i <= 100:
self.assertEqual(l.parse(u'A' * i), Tree('start', ['A']*i))
else:
self.assertRaises(UnexpectedInput, l.parse, u'A' * i)
# 8191 is a Mersenne prime
g = u"""start: "A"~8191
"""
l = Lark(g, parser='lalr')
self.assertEqual(l.parse(u'A' * 8191), Tree('start', []))
self.assertRaises(UnexpectedInput, l.parse, u'A' * 8190)
self.assertRaises(UnexpectedInput, l.parse, u'A' * 8192)
def test_large_terminal(self):
g = "start: NUMBERS\n"
g += "NUMBERS: " + '|'.join('"%s"' % i for i in range(0, 1000))
l = Lark(g, parser='lalr')
for i in (0, 9, 99, 999):
self.assertEqual(l.parse(str(i)), Tree('start', [str(i)]))
for i in (-1, 1000):
self.assertRaises(UnexpectedInput, l.parse, str(i))
def test_list_grammar_imports(self):
grammar = """
%import .test_templates_import (start, sep)
%override sep{item, delim}: item (delim item)* delim?
%ignore " "
"""
imports = list_grammar_imports(grammar, [os.path.dirname(__file__)])
self.assertEqual({os.path.split(i)[-1] for i in imports}, {'test_templates_import.lark', 'templates.lark'})
imports = list_grammar_imports('%import common.WS', [])
assert len(imports) == 1 and imports[0].pkg_name == 'lark'
def test_inline_with_expand_single(self):
grammar = r"""
start: _a
!?_a: "A"
"""
self.assertRaises(GrammarError, Lark, grammar)
def test_line_breaks(self):
p = Lark(r"""start: "a" \
"b"
""")
p.parse('ab')
if __name__ == '__main__':
main()
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