Lib/test/test_syntax.py

"""This module tests SyntaxErrors.

Here's an example of the sort of thing that is tested.

>>> def f(x):
...     global x
Traceback (most recent call last):
SyntaxError: name 'x' is local and global

The tests are all raise SyntaxErrors.  They were created by checking
each C call that raises SyntaxError.  There are several modules that
raise these exceptions-- ast.c, compile.c, future.c, pythonrun.c, and
symtable.c.

The parser itself outlaws a lot of invalid syntax.  None of these
errors are tested here at the moment.  We should add some tests; since
there are infinitely many programs with invalid syntax, we would need
to be judicious in selecting some.

The compiler generates a synthetic module name for code executed by
doctest.  Since all the code comes from the same module, a suffix like
[1] is appended to the module name, As a consequence, changing the
order of tests in this module means renumbering all the errors after
it.  (Maybe we should enable the ellipsis option for these tests.)

In ast.c, syntax errors are raised by calling ast_error().

Errors from set_context():

TODO(jhylton): "assignment to None" is inconsistent with other messages

>>> obj.None = 1
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[1]>, line 1)

>>> None = 1
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[2]>, line 1)

It's a syntax error to assign to the empty tuple.  Why isn't it an
error to assign to the empty list?  It will always raise some error at
runtime.

>>> () = 1
Traceback (most recent call last):
SyntaxError: can't assign to () (<doctest test.test_syntax[3]>, line 1)

>>> f() = 1
Traceback (most recent call last):
SyntaxError: can't assign to function call (<doctest test.test_syntax[4]>, line 1)

>>> del f()
Traceback (most recent call last):
SyntaxError: can't delete function call (<doctest test.test_syntax[5]>, line 1)

>>> a + 1 = 2
Traceback (most recent call last):
SyntaxError: can't assign to operator (<doctest test.test_syntax[6]>, line 1)

>>> (x for x in x) = 1
Traceback (most recent call last):
SyntaxError: can't assign to generator expression (<doctest test.test_syntax[7]>, line 1)

>>> 1 = 1
Traceback (most recent call last):
SyntaxError: can't assign to literal (<doctest test.test_syntax[8]>, line 1)

>>> "abc" = 1
Traceback (most recent call last):
SyntaxError: can't assign to literal (<doctest test.test_syntax[9]>, line 1)

>>> `1` = 1
Traceback (most recent call last):
SyntaxError: can't assign to repr (<doctest test.test_syntax[10]>, line 1)

If the left-hand side of an assignment is a list or tuple, an illegal
expression inside that contain should still cause a syntax error.
This test just checks a couple of cases rather than enumerating all of
them.

>>> (a, "b", c) = (1, 2, 3)
Traceback (most recent call last):
SyntaxError: can't assign to literal (<doctest test.test_syntax[11]>, line 1)

>>> [a, b, c + 1] = [1, 2, 3]
Traceback (most recent call last):
SyntaxError: can't assign to operator (<doctest test.test_syntax[12]>, line 1)


From compiler_complex_args():

>>> def f(None=1):
...     pass
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[13]>, line 1)


From ast_for_arguments():

>>> def f(x, y=1, z):
...     pass
Traceback (most recent call last):
SyntaxError: non-default argument follows default argument (<doctest test.test_syntax[14]>, line 1)

>>> def f(x, None):
...     pass
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[15]>, line 1)

>>> def f(*None):
...     pass
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[16]>, line 1)

>>> def f(**None):
...     pass
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[17]>, line 1)


From ast_for_funcdef():

>>> def None(x):
...     pass
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[18]>, line 1)


From ast_for_call():

>>> def f(it, *varargs):
...     return list(it)
>>> L = range(10)
>>> f(x for x in L)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> f(x for x in L, 1)
Traceback (most recent call last):
SyntaxError: Generator expression must be parenthesized if not sole argument (<doctest test.test_syntax[22]>, line 1)
>>> f((x for x in L), 1)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> f(i0,  i1,  i2,  i3,  i4,  i5,  i6,  i7,  i8,  i9,  i10,  i11,
...   i12,  i13,  i14,  i15,  i16,  i17,  i18,  i19,  i20,  i21,  i22,
...   i23,  i24,  i25,  i26,  i27,  i28,  i29,  i30,  i31,  i32,  i33,
...   i34,  i35,  i36,  i37,  i38,  i39,  i40,  i41,  i42,  i43,  i44,
...   i45,  i46,  i47,  i48,  i49,  i50,  i51,  i52,  i53,  i54,  i55,
...   i56,  i57,  i58,  i59,  i60,  i61,  i62,  i63,  i64,  i65,  i66,
...   i67,  i68,  i69,  i70,  i71,  i72,  i73,  i74,  i75,  i76,  i77,
...   i78,  i79,  i80,  i81,  i82,  i83,  i84,  i85,  i86,  i87,  i88,
...   i89,  i90,  i91,  i92,  i93,  i94,  i95,  i96,  i97,  i98,  i99,
...   i100,  i101,  i102,  i103,  i104,  i105,  i106,  i107,  i108,
...   i109,  i110,  i111,  i112,  i113,  i114,  i115,  i116,  i117,
...   i118,  i119,  i120,  i121,  i122,  i123,  i124,  i125,  i126,
...   i127,  i128,  i129,  i130,  i131,  i132,  i133,  i134,  i135,
...   i136,  i137,  i138,  i139,  i140,  i141,  i142,  i143,  i144,
...   i145,  i146,  i147,  i148,  i149,  i150,  i151,  i152,  i153,
...   i154,  i155,  i156,  i157,  i158,  i159,  i160,  i161,  i162,
...   i163,  i164,  i165,  i166,  i167,  i168,  i169,  i170,  i171,
...   i172,  i173,  i174,  i175,  i176,  i177,  i178,  i179,  i180,
...   i181,  i182,  i183,  i184,  i185,  i186,  i187,  i188,  i189,
...   i190,  i191,  i192,  i193,  i194,  i195,  i196,  i197,  i198,
...   i199,  i200,  i201,  i202,  i203,  i204,  i205,  i206,  i207,
...   i208,  i209,  i210,  i211,  i212,  i213,  i214,  i215,  i216,
...   i217,  i218,  i219,  i220,  i221,  i222,  i223,  i224,  i225,
...   i226,  i227,  i228,  i229,  i230,  i231,  i232,  i233,  i234,
...   i235,  i236,  i237,  i238,  i239,  i240,  i241,  i242,  i243,
...   i244,  i245,  i246,  i247,  i248,  i249,  i250,  i251,  i252,
...   i253,  i254,  i255)
Traceback (most recent call last):
SyntaxError: more than 255 arguments (<doctest test.test_syntax[24]>, line 1)

The actual error cases counts positional arguments, keyword arguments,
and generator expression arguments separately.  This test combines the
three.

>>> f(i0,  i1,  i2,  i3,  i4,  i5,  i6,  i7,  i8,  i9,  i10,  i11,
...   i12,  i13,  i14,  i15,  i16,  i17,  i18,  i19,  i20,  i21,  i22,
...   i23,  i24,  i25,  i26,  i27,  i28,  i29,  i30,  i31,  i32,  i33,
...   i34,  i35,  i36,  i37,  i38,  i39,  i40,  i41,  i42,  i43,  i44,
...   i45,  i46,  i47,  i48,  i49,  i50,  i51,  i52,  i53,  i54,  i55,
...   i56,  i57,  i58,  i59,  i60,  i61,  i62,  i63,  i64,  i65,  i66,
...   i67,  i68,  i69,  i70,  i71,  i72,  i73,  i74,  i75,  i76,  i77,
...   i78,  i79,  i80,  i81,  i82,  i83,  i84,  i85,  i86,  i87,  i88,
...   i89,  i90,  i91,  i92,  i93,  i94,  i95,  i96,  i97,  i98,  i99,
...   i100,  i101,  i102,  i103,  i104,  i105,  i106,  i107,  i108,
...   i109,  i110,  i111,  i112,  i113,  i114,  i115,  i116,  i117,
...   i118,  i119,  i120,  i121,  i122,  i123,  i124,  i125,  i126,
...   i127,  i128,  i129,  i130,  i131,  i132,  i133,  i134,  i135,
...   i136,  i137,  i138,  i139,  i140,  i141,  i142,  i143,  i144,
...   i145,  i146,  i147,  i148,  i149,  i150,  i151,  i152,  i153,
...   i154,  i155,  i156,  i157,  i158,  i159,  i160,  i161,  i162,
...   i163,  i164,  i165,  i166,  i167,  i168,  i169,  i170,  i171,
...   i172,  i173,  i174,  i175,  i176,  i177,  i178,  i179,  i180,
...   i181,  i182,  i183,  i184,  i185,  i186,  i187,  i188,  i189,
...   i190,  i191,  i192,  i193,  i194,  i195,  i196,  i197,  i198,
...   i199,  i200,  i201,  i202,  i203,  i204,  i205,  i206,  i207,
...   i208,  i209,  i210,  i211,  i212,  i213,  i214,  i215,  i216,
...   i217,  i218,  i219,  i220,  i221,  i222,  i223,  i224,  i225,
...   i226,  i227,  i228,  i229,  i230,  i231,  i232,  i233,  i234,
...   i235, i236,  i237,  i238,  i239,  i240,  i241,  i242,  i243,
...   (x for x in i244),  i245,  i246,  i247,  i248,  i249,  i250,  i251,
...    i252=1, i253=1,  i254=1,  i255=1)
Traceback (most recent call last):
SyntaxError: more than 255 arguments (<doctest test.test_syntax[25]>, line 1)

>>> f(lambda x: x[0] = 3)
Traceback (most recent call last):
SyntaxError: lambda cannot contain assignment (<doctest test.test_syntax[26]>, line 1)

The grammar accepts any test (basically, any expression) in the
keyword slot of a call site.  Test a few different options.

>>> f(x()=2)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression (<doctest test.test_syntax[27]>, line 1)
>>> f(a or b=1)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression (<doctest test.test_syntax[28]>, line 1)
>>> f(x.y=1)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression (<doctest test.test_syntax[29]>, line 1)


From ast_for_expr_stmt():

>>> (x for x in x) += 1
Traceback (most recent call last):
SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_syntax[30]>, line 1)
>>> None += 1
Traceback (most recent call last):
SyntaxError: assignment to None (<doctest test.test_syntax[31]>, line 1)
>>> f() += 1
Traceback (most recent call last):
SyntaxError: illegal expression for augmented assignment (<doctest test.test_syntax[32]>, line 1)
"""

import re
import unittest
import warnings

from test import test_support

class SyntaxTestCase(unittest.TestCase):

    def _check_error(self, code, errtext,
                     filename="<testcase>", mode="exec"):
        """Check that compiling code raises SyntaxError with errtext.

        errtest is a regular expression that must be present in the
        test of the exception raised.
        """
        try:
            compile(code, filename, mode)
        except SyntaxError, err:
            mo = re.search(errtext, str(err))
            if mo is None:
                self.fail("SyntaxError did not contain '%r'" % (errtext,))
        else:
            self.fail("compile() did not raise SyntaxError")

    def test_assign_call(self):
        self._check_error("f() = 1", "assign")

    def test_assign_del(self):
        self._check_error("del f()", "delete")

    def test_global_err_then_warn(self):
        # Bug tickler:  The SyntaxError raised for one global statement
        # shouldn't be clobbered by a SyntaxWarning issued for a later one.
        source = re.sub('(?m)^ *:', '', """\
            :def error(a):
            :    global a  # SyntaxError
            :def warning():
            :    b = 1
            :    global b  # SyntaxWarning
            :""")
        warnings.filterwarnings(action='ignore', category=SyntaxWarning)
        self._check_error(source, "global")
        warnings.filters.pop(0)

    def test_break_outside_loop(self):
        self._check_error("break", "outside loop")

    def test_delete_deref(self):
        source = re.sub('(?m)^ *:', '', """\
            :def foo(x):
            :  def bar():
            :    print x
            :  del x
            :""")
        self._check_error(source, "nested scope")

def test_main():
    test_support.run_unittest(SyntaxTestCase)
    from test import test_syntax
    test_support.run_doctest(test_syntax, verbosity=True)

if __name__ == "__main__":
    test_main()