cpython/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 parameter 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():

>>> obj.None = 1
Traceback (most recent call last):
SyntaxError: invalid syntax

>>> None = 1
Traceback (most recent call last):
SyntaxError: assignment to keyword (<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: invalid syntax

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)

>>> a if 1 else b = 1
Traceback (most recent call last):
SyntaxError: can't assign to conditional expression (<doctest test.test_syntax[13]>, line 1)

From compiler_complex_args():

>>> def f(None=1):
...     pass
Traceback (most recent call last):
SyntaxError: invalid syntax


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[15]>, line 1)

>>> def f(x, None):
...     pass
Traceback (most recent call last):
SyntaxError: invalid syntax

>>> def f(*None):
...     pass
Traceback (most recent call last):
SyntaxError: invalid syntax

>>> def f(**None):
...     pass
Traceback (most recent call last):
SyntaxError: invalid syntax


From ast_for_funcdef():

>>> def None(x):
...     pass
Traceback (most recent call last):
SyntaxError: invalid syntax


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[23]>, 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[25]>, 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[26]>, line 1)

>>> f(lambda x: x[0] = 3)
Traceback (most recent call last):
SyntaxError: lambda cannot contain assignment (<doctest test.test_syntax[27]>, 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[28]>, line 1)
>>> f(a or b=1)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression (<doctest test.test_syntax[29]>, line 1)
>>> f(x.y=1)
Traceback (most recent call last):
SyntaxError: keyword can't be an expression (<doctest test.test_syntax[30]>, 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[31]>, line 1)
>>> None += 1
Traceback (most recent call last):
SyntaxError: assignment to keyword (<doctest test.test_syntax[32]>, line 1)
>>> f() += 1
Traceback (most recent call last):
SyntaxError: illegal expression for augmented assignment (<doctest test.test_syntax[33]>, line 1)


Test continue in finally in weird combinations.

continue in for loop under finally shouuld be ok.

    >>> def test():
    ...     try:
    ...         pass
    ...     finally:
    ...         for abc in range(10):
    ...             continue
    ...     print(abc)
    >>> test()
    9

Start simple, a continue in a finally should not be allowed.

    >>> def test():
    ...    for abc in range(10):
    ...        try:
    ...            pass
    ...        finally:
    ...            continue
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[36]>, line 6)

This is essentially a continue in a finally which should not be allowed.

    >>> def test():
    ...    for abc in range(10):
    ...        try:
    ...            pass
    ...        finally:
    ...            try:
    ...                continue
    ...            except:
    ...                pass
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[37]>, line 7)

    >>> def foo():
    ...     try:
    ...         pass
    ...     finally:
    ...         continue
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[38]>, line 5)

    >>> def foo():
    ...     for a in ():
    ...       try:
    ...           pass
    ...       finally:
    ...           continue
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[39]>, line 6)

    >>> def foo():
    ...     for a in ():
    ...         try:
    ...             pass
    ...         finally:
    ...             try:
    ...                 continue
    ...             finally:
    ...                 pass
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[40]>, line 7)

    >>> def foo():
    ...  for a in ():
    ...   try: pass
    ...   finally:
    ...    try:
    ...     pass
    ...    except:
    ...     continue
    Traceback (most recent call last):
      ...
    SyntaxError: 'continue' not supported inside 'finally' clause (<doctest test.test_syntax[41]>, line 8)

There is one test for a break that is not in a loop.  The compiler
uses a single data structure to keep track of try-finally and loops,
so we need to be sure that a break is actually inside a loop.  If it
isn't, there should be a syntax error.

   >>> try:
   ...     print(1)
   ...     break
   ...     print(2)
   ... finally:
   ...     print(3)
   Traceback (most recent call last):
     ...
   SyntaxError: 'break' outside loop (<doctest test.test_syntax[42]>, line 3)

This should probably raise a better error than a SystemError (or none at all).
In 2.5 there was a missing exception and an assert was triggered in a debug
build.  The number of blocks must be greater than CO_MAXBLOCKS.  SF #1565514

   >>> while 1:
   ...  while 2:
   ...   while 3:
   ...    while 4:
   ...     while 5:
   ...      while 6:
   ...       while 8:
   ...        while 9:
   ...         while 10:
   ...          while 11:
   ...           while 12:
   ...            while 13:
   ...             while 14:
   ...              while 15:
   ...               while 16:
   ...                while 17:
   ...                 while 18:
   ...                  while 19:
   ...                   while 20:
   ...                    while 21:
   ...                     while 22:
   ...                      break
   Traceback (most recent call last):
     ...
   SystemError: too many statically nested blocks

Misuse of the nonlocal statement can lead to a few unique syntax errors.

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

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

   >>> def f():
   ...     nonlocal x
   Traceback (most recent call last):
     ...
   SyntaxError: no binding for nonlocal 'x' found

From SF bug #1705365
   >>> nonlocal x
   Traceback (most recent call last):
     ...
   SyntaxError: nonlocal declaration not allowed at module level

TODO(jhylton): Figure out how to test SyntaxWarning with doctest.

##   >>> def f(x):
##   ...     def f():
##   ...         print(x)
##   ...         nonlocal x
##   Traceback (most recent call last):
##     ...
##   SyntaxWarning: name 'x' is assigned to before nonlocal declaration

##   >>> def f():
##   ...     x = 1
##   ...     nonlocal x
##   Traceback (most recent call last):
##     ...
##   SyntaxWarning: name 'x' is assigned to before nonlocal declaration


This tests assignment-context; there was a bug in Python 2.5 where compiling
a complex 'if' (one with 'elif') would fail to notice an invalid suite,
leading to spurious errors.

   >>> if 1:
   ...   x() = 1
   ... elif 1:
   ...   pass
   Traceback (most recent call last):
     ...
   SyntaxError: can't assign to function call (<doctest test.test_syntax[48]>, line 2)

   >>> if 1:
   ...   pass
   ... elif 1:
   ...   x() = 1
   Traceback (most recent call last):
     ...
   SyntaxError: can't assign to function call (<doctest test.test_syntax[49]>, line 4)

   >>> if 1:
   ...   x() = 1
   ... elif 1:
   ...   pass
   ... else:
   ...   pass
   Traceback (most recent call last):
     ...
   SyntaxError: can't assign to function call (<doctest test.test_syntax[50]>, line 2)

   >>> if 1:
   ...   pass
   ... elif 1:
   ...   x() = 1
   ... else:
   ...   pass
   Traceback (most recent call last):
     ...
   SyntaxError: can't assign to function call (<doctest test.test_syntax[51]>, line 4)

   >>> if 1:
   ...   pass
   ... elif 1:
   ...   pass
   ... else:
   ...   x() = 1
   Traceback (most recent call last):
     ...
   SyntaxError: can't assign to function call (<doctest test.test_syntax[52]>, line 6)

"""

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", subclass=None):
        """Check that compiling code raises SyntaxError with errtext.

        errtest is a regular expression that must be present in the
        test of the exception raised.  If subclass is specified it
        is the expected subclass of SyntaxError (e.g. IndentationError).
        """
        try:
            compile(code, filename, mode)
        except SyntaxError as err:
            if subclass and not isinstance(err, subclass):
                self.fail("SyntaxError is not a %s" % subclass.__name__)
            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_unexpected_indent(self):
        self._check_error("foo()\n bar()\n", "unexpected indent",
                          subclass=IndentationError)

    def test_no_indent(self):
        self._check_error("if 1:\nfoo()", "expected an indented block",
                          subclass=IndentationError)

    def test_bad_outdent(self):
        self._check_error("if 1:\n  foo()\n bar()",
                          "unindent does not match .* level",
                          subclass=IndentationError)

    def test_kwargs_last(self):
        self._check_error("int(base=10, '2')", "non-keyword arg")

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()