test_simpleeval.py

"""
    Unit tests for simpleeval.
    --------------------------

    Most of this stuff is pretty basic.

"""
# pylint: disable=too-many-public-methods, missing-docstring
import sys
import unittest
import operator
import ast
import simpleeval
import os
import warnings
from simpleeval import (
    SimpleEval, EvalWithCompoundTypes, FeatureNotAvailable, FunctionNotDefined, NameNotDefined,
    InvalidExpression, AttributeDoesNotExist, simple_eval
)


class DRYTest(unittest.TestCase):
    """ Stuff we need to do every test, let's do here instead..
        Don't Repeat Yourself. """

    def setUp(self):
        """ initialize a SimpleEval """
        self.s = SimpleEval()

    def t(self, expr, shouldbe):  # pylint: disable=invalid-name
        """ test an evaluation of an expression against an expected answer """
        return self.assertEqual(self.s.eval(expr), shouldbe)


class TestBasic(DRYTest):
    """ Simple expressions. """

    def test_maths_with_ints(self):
        """ simple maths expressions """

        self.t("21 + 21", 42)
        self.t("6*7", 42)
        self.t("20 + 1 + (10*2) + 1", 42)
        self.t("100/10", 10)
        self.t("12*12", 144)
        self.t("2 ** 10", 1024)
        self.t("100 % 9", 1)

    def test_bools_and_or(self):
        self.t('True and ""', "")
        self.t('True and False', False)
        self.t('True or False', True)
        self.t('False or False', False)
        self.t('1 - 1 or 21', 21)
        self.t('1 - 1 and 11', 0)
        self.t('110 == 100 + 10 and True', True)
        self.t('110 != 100 + 10 and True', False)
        self.t('False or 42', 42)

        self.t('False or None', None)
        self.t('None or None', None)

        self.s.names = {'out': True, 'position': 3}
        self.t('(out and position <=6 and -10)'
               ' or (out and position > 6 and -5)'
               ' or (not out and 15)', -10)

    def test_not(self):
        self.t('not False', True)
        self.t('not True', False)
        self.t('not 0', True)
        self.t('not 1', False)

    def test_maths_with_floats(self):
        self.t("11.02 - 9.1", 1.92)
        self.t("29.1+39", 68.1)

    def test_comparisons(self):
        # GT & LT:
        self.t("1 > 0", True)
        self.t("100000 < 28", False)
        self.t("-2 < 11", True)
        self.t("+2 < 5", True)
        self.t("0 == 0", True)

        # GtE, LtE
        self.t("-2 <= -2", True)
        self.t("2 >= 2", True)
        self.t("1 >= 12", False)
        self.t("1.09 <= 1967392", True)

        self.t('1 < 2 < 3 < 4', 1 < 2 < 3 < 4)
        self.t('1 < 2 > 3 < 4', 1 < 2 > 3 < 4)

        self.t('1<2<1+1', 1 < 2 < 1 + 1)
        self.t('1 == 1 == 2', 1 == 1 == 2)
        self.t('1 == 1 < 2', 1 == 1 < 2)

    def test_mixed_comparisons(self):
        self.t("1 > 0.999999", True)
        self.t("1 == True", True)  # Note ==, not 'is'.
        self.t("0 == False", True)  # Note ==, not 'is'.
        self.t("False == False", True)
        self.t("False < True", True)

    def test_if_else(self):
        """ x if y else z """

        # and test if/else expressions:
        self.t("'a' if 1 == 1 else 'b'", 'a')
        self.t("'a' if 1 > 2 else 'b'", 'b')

        # and more complex expressions:
        self.t("'a' if 4 < 1 else 'b' if 1 == 2 else 'c'", 'c')

    def test_default_conversions(self):
        """ conversion between types """

        self.t('int("20") + int(0.22*100)', 42)
        self.t('float("42")', 42.0)
        self.t('"Test Stuff!" + str(11)', "Test Stuff!11")

    def test_slicing(self):
        self.s.operators[ast.Slice] = (operator.getslice
                                       if hasattr(operator, "getslice") else operator.getitem)
        self.t("'hello'[1]", "e")
        self.t("'hello'[:]", "hello")
        self.t("'hello'[:3]", "hel")
        self.t("'hello'[3:]", "lo")
        self.t("'hello'[::2]", "hlo")
        self.t("'hello'[::-1]", "olleh")
        self.t("'hello'[3::]", "lo")
        self.t("'hello'[:3:]", "hel")
        self.t("'hello'[1:3]", "el")
        self.t("'hello'[1:3:]", "el")
        self.t("'hello'[1::2]", "el")
        self.t("'hello'[:1:2]", "h")
        self.t("'hello'[1:3:1]", "el")
        self.t("'hello'[1:3:2]", "e")

        with self.assertRaises(IndexError):
            self.t("'hello'[90]", 0)

        self.t('"spam" not in "my breakfast"', True)
        self.t('"silly" in "ministry of silly walks"', True)
        self.t('"I" not in "team"', True)
        self.t('"U" in "RUBBISH"', True)

    def test_is(self):
        self.t('1 is 1', True)
        self.t('1 is 2', False)
        self.t('1 is "a"', False)
        self.t('1 is None', False)
        self.t('None is None', True)

        self.t('1 is not 1', False)
        self.t('1 is not 2', True)
        self.t('1 is not "a"', True)
        self.t('1 is not None', True)
        self.t('None is not None', False)

    def test_fstring(self):
        if sys.version_info >= (3, 6, 0):
            self.t('f""', "")
            self.t('f"stuff"', "stuff")
            self.t('f"one is {1} and two is {2}"', "one is 1 and two is 2")
            self.t('f"1+1 is {1+1}"', "1+1 is 2")
            self.t('f"{\'dramatic\':!<11}"', "dramatic!!!")

    def test_set_not_allowed(self):
        with self.assertRaises(FeatureNotAvailable):
            self.t('{22}', False)


class TestFunctions(DRYTest):
    """ Functions for expressions to play with """

    def test_load_file(self):
        """ add in a function which loads data from an external file. """

        # write to the file:

        with open("testfile.txt", 'w') as f:
            f.write("42")

        # define the function we'll send to the eval'er

        def load_file(filename):
            """ load a file and return its contents """
            with open(filename) as f2:
                return f2.read()

        # simple load:

        self.s.functions = {"read": load_file}
        self.t("read('testfile.txt')", "42")

        # and we should have *replaced* the default functions. Let's check:

        with self.assertRaises(simpleeval.FunctionNotDefined):
            self.t("int(read('testfile.txt'))", 42)

        # OK, so we can load in the default functions as well...

        self.s.functions.update(simpleeval.DEFAULT_FUNCTIONS)

        # now it works:

        self.t("int(read('testfile.txt'))", 42)

        os.remove('testfile.txt')

    def test_randoms(self):
        """ test the rand() and randint() functions """

        i = self.s.eval('randint(1000)')
        self.assertEqual(type(i), int)
        self.assertLessEqual(i, 1000)

        f = self.s.eval('rand()')
        self.assertEqual(type(f), float)

        self.t("randint(20)<20", True)
        self.t("rand()<1.0", True)

        # I don't know how to further test these functions.  Ideas?

    def test_methods(self):
        self.t('"WORD".lower()', 'word')
        x = simpleeval.DISALLOW_METHODS
        simpleeval.DISALLOW_METHODS = []
        self.t('"{}:{}".format(1, 2)', '1:2')
        simpleeval.DISALLOW_METHODS = x

    def test_function_args_none(self):
        def foo():
            return 42

        self.s.functions['foo'] = foo
        self.t('foo()', 42)

    def test_function_args_required(self):
        def foo(toret):
            return toret

        self.s.functions['foo'] = foo
        with self.assertRaises(TypeError):
            self.t('foo()', 42)

        self.t('foo(12)', 12)
        self.t('foo(toret=100)', 100)

    def test_function_args_defaults(self):
        def foo(toret=9999):
            return toret

        self.s.functions['foo'] = foo
        self.t('foo()', 9999)

        self.t('foo(12)', 12)
        self.t('foo(toret=100)', 100)

    def test_function_args_bothtypes(self):
        def foo(mult, toret=100):
            return toret * mult

        self.s.functions['foo'] = foo
        with self.assertRaises(TypeError):
            self.t('foo()', 9999)

        self.t('foo(2)', 200)

        with self.assertRaises(TypeError):
            self.t('foo(toret=100)', 100)

        self.t('foo(4, toret=4)', 16)
        self.t('foo(mult=2, toret=4)', 8)
        self.t('foo(2, 10)', 20)


class TestOperators(DRYTest):
    """ Test adding in new operators, removing them, make sure it works. """
    # TODO
    pass

class TestNewFeatures(DRYTest):
    """ Tests which will break when new features are added..."""
    def test_lambda(self):
        with self.assertRaises(FeatureNotAvailable):
            self.t('lambda x:22', None)

    def test_lambda_application(self):
        with self.assertRaises(FeatureNotAvailable):
            self.t('(lambda x:22)(44)', None)


class TestTryingToBreakOut(DRYTest):
    """ Test various weird methods to break the security sandbox... """

    def test_import(self):
        """ usual suspect. import """
        # cannot import things:
        with self.assertRaises(FeatureNotAvailable):
            self.t("import sys", None)

    def test_long_running(self):
        """ exponent operations can take a long time. """
        old_max = simpleeval.MAX_POWER

        self.t("9**9**5", 9 ** 9 ** 5)

        with self.assertRaises(simpleeval.NumberTooHigh):
            self.t("9**9**8", 0)

        # and does limiting work?

        simpleeval.MAX_POWER = 100

        with self.assertRaises(simpleeval.NumberTooHigh):
            self.t("101**2", 0)

        # good, so set it back:

        simpleeval.MAX_POWER = old_max

    def test_encode_bignums(self):
        # thanks gk
        if hasattr(1, 'from_bytes'):  # python3 only
            with self.assertRaises(simpleeval.IterableTooLong):
                self.t('(1).from_bytes(("123123123123123123123123").encode()*999999, "big")', 0)

    def test_string_length(self):
        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("50000*'text'", 0)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("'text'*50000", 0)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("('text'*50000)*1000", 0)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("(50000*'text')*1000", 0)

        self.t("'stuff'*20000", 20000 * 'stuff')

        self.t("20000*'stuff'", 20000 * 'stuff')

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("('stuff'*20000) + ('stuff'*20000) ", 0)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("'stuff'*100000", 100000 * 'stuff')

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("'" + (10000 * "stuff") + "'*100", 0)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("'" + (50000 * "stuff") + "'", 0)

        if sys.version_info >= (3, 6, 0):
            with self.assertRaises(simpleeval.IterableTooLong):
                self.t("f'{\"foo\"*50000}'", 0)

    def test_bytes_array_test(self):
        self.t("'20000000000000000000'.encode() * 5000",
               '20000000000000000000'.encode() * 5000)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("'123121323123131231223'.encode() * 5000", 20)

    def test_list_length_test(self):
        self.t("'spam spam spam'.split() * 5000", ['spam', 'spam', 'spam'] * 5000)

        with self.assertRaises(simpleeval.IterableTooLong):
            self.t("('spam spam spam' * 5000).split() * 5000", None)

    def test_python_stuff(self):
        """ other various pythony things. """
        # it only evaluates the first statement:
        self.t("11; x = 21; x + x", 11)


    def test_function_globals_breakout(self):
        """ by accessing function.__globals__ or func_... """
        # thanks perkinslr.

        self.s.functions['x'] = lambda y: y + y
        self.t('x(100)', 200)

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t('x.__globals__', None)

        class EscapeArtist(object):
            @staticmethod
            def trapdoor():
                return 42

            @staticmethod
            def _quasi_private():
                return 84

        self.s.names['houdini'] = EscapeArtist()

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t('houdini.trapdoor.__globals__', 0)

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t('houdini.trapdoor.func_globals', 0)

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t('houdini._quasi_private()', 0)

        # and test for changing '_' to '__':

        dis = simpleeval.DISALLOW_PREFIXES
        simpleeval.DISALLOW_PREFIXES = ['func_']

        self.t('houdini.trapdoor()', 42)
        self.t('houdini._quasi_private()', 84)

        # and return things to normal

        simpleeval.DISALLOW_PREFIXES = dis

    def test_mro_breakout(self):
        class Blah(object):
            x = 42

        self.s.names['b'] = Blah

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t('b.mro()', None)

    def test_builtins_private_access(self):
        # explicit attempt of the exploit from perkinslr
        with self.assertRaises(simpleeval.FeatureNotAvailable):
            self.t("True.__class__.__class__.__base__.__subclasses__()[-1]"
                   ".__init__.func_globals['sys'].exit(1)", 42)


    def test_string_format(self):
        # python has so many ways to break out!
        with self.assertRaises(simpleeval.FeatureNotAvailable):
             self.t('"{string.__class__}".format(string="things")', 0)

        with self.assertRaises(simpleeval.FeatureNotAvailable):
             self.s.names['x'] = {"a": 1}
             self.t('"{a.__class__}".format_map(x)', 0)

        if sys.version_info >= (3, 6, 0):
            self.s.names['x'] = 42

            with self.assertRaises(simpleeval.FeatureNotAvailable):
                self.t('f"{x.__class__}"', 0)

            self.s.names['x'] = lambda y: y

            with self.assertRaises(simpleeval.FeatureNotAvailable):
                self.t('f"{x.__globals__}"', 0)

            class EscapeArtist(object):
                @staticmethod
                def trapdoor():
                    return 42

                @staticmethod
                def _quasi_private():
                    return 84

            self.s.names['houdini'] = EscapeArtist()  # let's just retest this, but in a f-string

            with self.assertRaises(simpleeval.FeatureNotAvailable):
                self.t('f"{houdini.trapdoor.__globals__}"', 0)

            with self.assertRaises(simpleeval.FeatureNotAvailable):
                self.t('f"{houdini.trapdoor.func_globals}"', 0)

            with self.assertRaises(simpleeval.FeatureNotAvailable):
                self.t('f"{houdini._quasi_private()}"', 0)

            # and test for changing '_' to '__':

            dis = simpleeval.DISALLOW_PREFIXES
            simpleeval.DISALLOW_PREFIXES = ['func_']

            self.t('f"{houdini.trapdoor()}"', "42")
            self.t('f"{houdini._quasi_private()}"', "84")

            # and return things to normal

            simpleeval.DISALLOW_PREFIXES = dis



class TestCompoundTypes(DRYTest):
    """ Test the compound-types edition of the library """

    def setUp(self):
        self.s = EvalWithCompoundTypes()

    def test_dict(self):
        self.t('{}', {})
        self.t('{"foo": "bar"}', {'foo': 'bar'})
        self.t('{"foo": "bar"}["foo"]', 'bar')
        self.t('dict()', {})
        self.t('dict(a=1)', {'a': 1})

    def test_dict_contains(self):
        self.t('{"a":22}["a"]', 22)
        with self.assertRaises(KeyError):
            self.t('{"a":22}["b"]', 22)

        self.t('{"a": 24}.get("b", 11)', 11)
        self.t('"a" in {"a": 24}', True)

    def test_tuple(self):
        self.t('()', ())
        self.t('(1,)', (1,))
        self.t('(1, 2, 3, 4, 5, 6)', (1, 2, 3, 4, 5, 6))
        self.t('(1, 2) + (3, 4)', (1, 2, 3, 4))
        self.t('(1, 2, 3)[1]', 2)
        self.t('tuple()', ())
        self.t('tuple("foo")', ('f', 'o', 'o'))

    def test_tuple_contains(self):
        self.t('("a","b")[1]', 'b')
        with self.assertRaises(IndexError):
            self.t('("a","b")[5]', 'b')
        self.t('"a" in ("b","c","a")', True)

    def test_list(self):
        self.t('[]', [])
        self.t('[1]', [1])
        self.t('[1, 2, 3, 4, 5]', [1, 2, 3, 4, 5])
        self.t('[1, 2, 3][1]', 2)
        self.t('list()', [])
        self.t('list("foo")', ['f', 'o', 'o'])

    def test_list_contains(self):
        self.t('["a","b"][1]', 'b')
        with self.assertRaises(IndexError):
            self.t('("a","b")[5]', 'b')

        self.t('"b" in ["a","b"]', True)

    def test_set(self):
        self.t('{1}', {1})
        self.t('{1, 2, 1, 2, 1, 2, 1}', {1, 2})
        self.t('set()', set())
        self.t('set("foo")', {'f', 'o'})

        self.t('2 in {1,2,3,4}', True)
        self.t('22 not in {1,2,3,4}', True)

    def test_not(self):
        self.t('not []', True)
        self.t('not [0]', False)
        self.t('not {}', True)
        self.t('not {0: 1}', False)
        self.t('not {0}', False)

    def test_use_func(self):
        self.s = EvalWithCompoundTypes(functions={"map": map, "str": str})
        self.t('list(map(str, [-1, 0, 1]))', ['-1', '0', '1'])
        with self.assertRaises(NameNotDefined):
            self.s.eval('list(map(bad, [-1, 0, 1]))')

        with self.assertRaises(FunctionNotDefined):
            self.s.eval('dir(str)')
        with self.assertRaises(FeatureNotAvailable):
            self.s.eval('str.__dict__')

        self.s = EvalWithCompoundTypes(functions={"dir": dir, "str": str})
        self.t('dir(str)', dir(str))


class TestComprehensions(DRYTest):
    """ Test the comprehensions support of the compound-types edition of the class. """

    def setUp(self):
        self.s = EvalWithCompoundTypes()

    def test_basic(self):
        self.t('[a + 1 for a in [1,2,3]]', [2,3,4])

    def test_with_self_reference(self):
        self.t('[a + a for a in [1,2,3]]', [2,4,6])

    def test_with_if(self):
        self.t('[a for a in [1,2,3,4,5] if a <= 3]', [1,2,3])

    def test_with_multiple_if(self):
        self.t('[a for a in [1,2,3,4,5] if a <= 3 and a > 1 ]', [2,3])

    def test_attr_access_fails(self):
        with self.assertRaises(FeatureNotAvailable):
            self.t('[a.__class__ for a in [1,2,3]]', None)

    def test_unpack(self):
        self.t('[a+b for a,b in ((1,2),(3,4))]', [3, 7])

    def test_nested_unpack(self):
        self.t('[a+b+c for a, (b, c) in ((1,(1,1)),(3,(2,2)))]', [3, 7])

    def test_other_places(self):
        self.s.functions = {'sum': sum}
        self.t('sum([a+1 for a in [1,2,3,4,5]])', 20)
        self.t('sum(a+1 for a in [1,2,3,4,5])', 20)

    def test_external_names_work(self):
        self.s.names = {'x': [22, 102, 12.3]}
        self.t('[a/2 for a in x]', [11.0, 51.0, 6.15])

        self.s.names = lambda x: ord(x.id)
        self.t('[a + a for a in [b, c, d]]', [ord(x) * 2 for x in 'bcd'])

    def test_multiple_generators(self):
        self.s.functions = {'range': range}
        s = '[j for i in range(100) if i > 10 for j in range(i) if j < 20]'
        self.t(s, eval(s))

    def test_triple_generators(self):
        self.s.functions = {'range': range}
        s = '[(a,b,c) for a in range(4) for b in range(a) for c in range(b)]'
        self.t(s, eval(s))

    def test_too_long_generator(self):
        self.s.functions = {'range': range}
        s = '[j for i in range(1000) if i > 10 for j in range(i) if j < 20]'
        with self.assertRaises(simpleeval.IterableTooLong):
            self.s.eval(s)

    def test_too_long_generator_2(self):
        self.s.functions = {'range': range}
        s = '[j for i in range(100) if i > 1 for j in range(i+10) if j < 100 for k in range(i*j)]'
        with self.assertRaises(simpleeval.IterableTooLong):
            self.s.eval(s)

    def test_nesting_generators_to_cheat(self):
        self.s.functions = {'range': range}
        s = '[[[c for c in range(a)] for a in range(b)] for b in range(200)]'

        with self.assertRaises(simpleeval.IterableTooLong):
            self.s.eval(s)

    def test_no_leaking_names(self):
        # see issue #52, failing list comprehensions could leak locals
        with self.assertRaises(simpleeval.NameNotDefined):
            self.s.eval('[x if x == "2" else y for x in "123"]')

        with self.assertRaises(simpleeval.NameNotDefined):
            self.s.eval('x')


class TestNames(DRYTest):
    """ 'names', what other languages call variables... """

    def test_none(self):
        """ what to do when names isn't defined, or is 'none' """
        with self.assertRaises(NameNotDefined):
            self.t("a == 2", None)

        self.s.names["s"] = 21

        with self.assertRaises(NameNotDefined):
            with warnings.catch_warnings(record=True) as ws:
                self.t("s += a", 21)

        self.s.names = None

        with self.assertRaises(InvalidExpression):
            self.t('s', 21)

        self.s.names = {'a': {'b': {'c': 42}}}

        with self.assertRaises(AttributeDoesNotExist):
            self.t('a.b.d**2', 42)

    def test_dict(self):
        """ using a normal dict for names lookup """

        self.s.names = {'a': 42}
        self.t("a + a", 84)

        self.s.names['also'] = 100

        self.t("a + also - a", 100)

        # however, you can't assign to those names:
        with warnings.catch_warnings(record=True) as ws:
            self.t("a = 200", 200)

        self.assertEqual(self.s.names['a'], 42)

        # or assign to lists

        self.s.names['b'] = [0]

        with warnings.catch_warnings(record=True) as ws:
            self.t("b[0] = 11", 11)

        self.assertEqual(self.s.names['b'], [0])

        # but you can get items from a list:

        self.s.names['b'] = [6, 7]

        self.t("b[0] * b[1]", 42)

        # or from a dict

        self.s.names['c'] = {'i': 11}

        self.t("c['i']", 11)
        self.t("c.get('i')", 11)
        self.t("c.get('j', 11)", 11)
        self.t("c.get('j')", None)

        # you still can't assign though:

        with warnings.catch_warnings(record=True) as ws:
            self.t("c['b'] = 99", 99)

        self.assertFalse('b' in self.s.names['c'])

        # and going all 'inception' on it doesn't work either:

        self.s.names['c']['c'] = {'c': 11}

        with warnings.catch_warnings(record=True) as ws:
            self.t("c['c']['c'] = 21", 21)

        self.assertEqual(self.s.names['c']['c']['c'], 11)

    def test_dict_attr_access(self):
        # nested dict

        self.assertEqual(self.s.ATTR_INDEX_FALLBACK, True)

        self.s.names = {'a': {'b': {'c': 42}}}

        self.t("a.b.c*2", 84)

        with warnings.catch_warnings(record=True) as ws:
            self.t("a.b.c = 11", 11)

        self.assertEqual(self.s.names['a']['b']['c'], 42)

        # TODO: Wat?
        with warnings.catch_warnings(record=True) as ws:
            self.t("a.d = 11", 11)

        with self.assertRaises(KeyError):
            self.assertEqual(self.s.names['a']['d'], 11)

    def test_dict_attr_access_disabled(self):
        # nested dict

        self.s.ATTR_INDEX_FALLBACK = False
        self.assertEqual(self.s.ATTR_INDEX_FALLBACK, False)

        self.s.names = {'a': {'b': {'c': 42}}}

        with self.assertRaises(simpleeval.AttributeDoesNotExist):
            self.t("a.b.c * 2", 84)

        self.t("a['b']['c'] * 2", 84)

        self.assertEqual(self.s.names['a']['b']['c'], 42)


    def test_object(self):
        """ using an object for name lookup """

        class TestObject(object):
            @staticmethod
            def method_thing():
                return 42

        o = TestObject()
        o.a = 23
        o.b = 42
        o.c = TestObject()
        o.c.d = 9001

        self.s.names = {'o': o}

        self.t('o', o)
        self.t('o.a', 23)
        self.t('o.b + o.c.d', 9043)

        self.t('o.method_thing()', 42)

        with self.assertRaises(AttributeDoesNotExist):
            self.t('o.d', None)

    def test_func(self):
        """ using a function for 'names lookup' """

        def resolver(_):
            """ all names now equal 1024! """
            return 1024

        self.s.names = resolver

        self.t("a", 1024)
        self.t("a + b - c - d", 0)

        # the function can do stuff with the value it's sent:

        def my_name(node):
            """ all names equal their textual name, twice. """
            return node.id + node.id

        self.s.names = my_name

        self.t("a", "aa")

    def test_from_doc(self):
        """ the 'name first letter as value' example from the docs """

        def name_handler(node):
            """ return the alphabet number of the first letter of
                the name's textual name """
            return ord(node.id[0].lower()) - 96

        self.s.names = name_handler
        self.t('a', 1)
        self.t('a + b', 3)


class TestWhitespace(DRYTest):
    """ test that incorrect whitespace (preceding/trailing) doesn't matter. """

    def test_no_whitespace(self):
        self.t('200 + 200', 400)

    def test_trailing(self):
        self.t('200 + 200       ', 400)

    def test_preciding_whitespace(self):
        self.t('    200 + 200', 400)

    def test_preceding_tab_whitespace(self):
        self.t("\t200 + 200", 400)

    def test_preceding_mixed_whitespace(self):
        self.t("  \t 200 + 200", 400)

    def test_both_ends_whitespace(self):
        self.t("  \t 200 + 200  ", 400)


class TestSimpleEval(unittest.TestCase):
    """ test the 'simple_eval' wrapper function """

    def test_basic_run(self):
        self.assertEqual(simple_eval('6*7'), 42)

    def test_default_functions(self):
        self.assertEqual(simple_eval('rand() < 1.0 and rand() > -0.01'), True)
        self.assertEqual(simple_eval('randint(200) < 200 and rand() > 0'), True)


class TestMethodChaining(unittest.TestCase):
    def test_chaining_correct(self):
        """
            Contributed by Khalid Grandi (xaled).
        """
        class A(object):
            def __init__(self):
                self.a = "0"

            def add(self, b):
                self.a += "-add" + str(b)
                return self

            def sub(self, b):
                self.a += "-sub" + str(b)
                return self

            def tostring(self):
                return str(self.a)

        x = A()
        self.assertEqual(simple_eval("x.add(1).sub(2).sub(3).tostring()", names={"x": x}), "0-add1-sub2-sub3")

class TestExtendingClass(unittest.TestCase):
    """
        It should be pretty easy to extend / inherit from the SimpleEval class,
        to further lock things down, or unlock stuff, or whatever.
    """

    def test_methods_forbidden(self):
        # Example from README
        class EvalNoMethods(simpleeval.SimpleEval):
            def _eval_call(self, node):
                if isinstance(node.func, ast.Attribute):
                    raise simpleeval.FeatureNotAvailable("No methods please, we're British")
                return super(EvalNoMethods, self)._eval_call(node)

        e = EvalNoMethods()

        self.assertEqual(e.eval('"stuff happens"'), "stuff happens")
        self.assertEqual(e.eval('22 + 20'), 42)
        self.assertEqual(e.eval('int("42")'), 42)

        with self.assertRaises(simpleeval.FeatureNotAvailable):
            e.eval('"  blah  ".strip()')


class TestExceptions(unittest.TestCase):
    """
        confirm a few attributes exist properly and haven't been
        eaten by 2to3 or whatever... (see #41)
    """

    def test_functionnotdefined(self):
        try:
            raise FunctionNotDefined("foo", "foo in bar")
        except FunctionNotDefined as e:
            assert hasattr(e, 'func_name')
            assert getattr(e, 'func_name') == 'foo'
            assert hasattr(e, 'expression')
            assert getattr(e, 'expression') == 'foo in bar'

    def test_namenotdefined(self):
        try:
            raise NameNotDefined("foo", "foo in bar")
        except NameNotDefined as e:
            assert hasattr(e, 'name')
            assert getattr(e, 'name') == 'foo'
            assert hasattr(e, 'expression')
            assert getattr(e, 'expression') == 'foo in bar'


    def test_attributedoesnotexist(self):
        try:
            raise AttributeDoesNotExist("foo", "foo in bar")
        except AttributeDoesNotExist as e:
            assert hasattr(e, 'attr')
            assert getattr(e, 'attr') == 'foo'
            assert hasattr(e, 'expression')
            assert getattr(e, 'expression') == 'foo in bar'

class TestUnusualComparisons(DRYTest):
    def test_custom_comparison_returner(self):
        class Blah(object):
            def __gt__(self, other):
                return self

        b = Blah()
        self.s.names = {'b': b}
        self.t('b > 2', b)

    def test_custom_comparison_doesnt_return_boolable(self):
        """
            SqlAlchemy, bless it's cotton socks, returns BinaryExpression objects
            when asking for comparisons between things.  These BinaryExpressions
            raise a TypeError if you try and check for Truthyiness.
        """
        class BinaryExpression(object):
            def __init__(self, value):
                self.value = value
            def __eq__(self, other):
                return self.value == getattr(other, 'value', other)
            def __repr__(self):
                return '<BinaryExpression:{}>'.format(self.value)
            def __bool__(self):
                # This is the only important part, to match SqlAlchemy - the rest
                # of the methods are just to make testing a bit easier...
                raise TypeError("Boolean value of this clause is not defined")

        class Blah(object):
            def __gt__(self, other):
                return BinaryExpression('GT')
            def __lt__(self, other):
                return BinaryExpression('LT')

        b = Blah()
        self.s.names = {'b': b}
        # This should not crash:
        e = eval('b > 2', self.s.names)

        self.t('b > 2', BinaryExpression('GT'))
        self.t('1 < 5 > b', BinaryExpression('LT'))

class TestGetItemUnhappy(DRYTest):
    # Again, SqlAlchemy doing unusual things.  Throwing it's own errors, rather than
    # expected types...

    def test_getitem_not_implemented(self):
        class Meh(object):
            def __getitem__(self, key):
                raise NotImplementedError("booya!")
            def __getattr__(self, key):
                return 42

        m = Meh()

        self.assertEqual(m.anything, 42)
        with self.assertRaises(NotImplementedError):
            m['nothing']

        self.s.names = {"m": m}
        self.t("m.anything", 42)

        with self.assertRaises(NotImplementedError):
            self.t("m['nothing']", None)

        self.s.ATTR_INDEX_FALLBACK = False

        self.t("m.anything", 42)

        with self.assertRaises(NotImplementedError):
            self.t("m['nothing']", None)


class TestShortCircuiting(DRYTest):
    def test_shortcircuit_if(self):
        x = []
        def foo(y):
            x.append(y)
            return y
        self.s.functions = {'foo': foo}
        self.t('foo(1) if foo(2) else foo(3)', 1)
        self.assertListEqual(x, [2, 1])

        x = []
        self.t('42 if True else foo(99)', 42)
        self.assertListEqual(x, [])

    def test_shortcircuit_comparison(self):
        x = []
        def foo(y):
            x.append(y)
            return y
        self.s.functions = {'foo': foo}
        self.t('foo(11) < 12', True)
        self.assertListEqual(x, [11])
        x = []

        self.t('1 > 2 < foo(22)', False)
        self.assertListEqual(x, [])


class TestDisallowedFunctions(DRYTest):
    def test_functions_are_disallowed_at_init(self):
        DISALLOWED = [type, isinstance, eval, getattr, setattr, help, repr, compile, open]
        if simpleeval.PYTHON3:
            exec('DISALLOWED.append(exec)') # exec is not a function in Python2...

        for f in simpleeval.DISALLOW_FUNCTIONS:
            assert f in DISALLOWED

        for x in DISALLOWED:
            with self.assertRaises(FeatureNotAvailable):
                s = SimpleEval(functions ={'foo': x})

    def test_functions_are_disallowed_in_expressions(self):
        DISALLOWED = [type, isinstance, eval, getattr, setattr, help, repr, compile, open]

        if simpleeval.PYTHON3:
            exec('DISALLOWED.append(exec)') # exec is not a function in Python2...

        for f in simpleeval.DISALLOW_FUNCTIONS:
            assert f in DISALLOWED


        DF = simpleeval.DEFAULT_FUNCTIONS.copy()

        for x in DISALLOWED:
            simpleeval.DEFAULT_FUNCTIONS = DF.copy()
            with self.assertRaises(FeatureNotAvailable):
                s = SimpleEval()
                s.functions['foo'] = x
                s.eval('foo(42)')

        simpleeval.DEFAULT_FUNCTIONS = DF.copy()


if __name__ == '__main__':  # pragma: no cover
    unittest.main()