• Neal Norwitz's avatar
    Fix SF bug #1167751, Argument genexp corner case · 37c0844b
    Neal Norwitz yazdı
    Incorrect code was generated for:
    
      foo(a = i for i in range(10))
    
    This should have generated a SyntaxError.  Fix the Grammar so
    it raises a SyntaxError and test it.
    
    I'm uncertain whether this should be backported.  It makes
    something that was Syntactically valid invalid.  However,
    the code would either be completely broken or do the wrong thing.
    37c0844b
test_genexps.py 7.1 KB
doctests = """

Test simple loop with conditional

    >>> sum(i*i for i in range(100) if i&1 == 1)
    166650

Test simple nesting

    >>> list((i,j) for i in range(3) for j in range(4) )
    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]

Test nesting with the inner expression dependent on the outer

    >>> list((i,j) for i in range(4) for j in range(i) )
    [(1, 0), (2, 0), (2, 1), (3, 0), (3, 1), (3, 2)]

Make sure the induction variable is not exposed

    >>> i = 20
    >>> sum(i*i for i in range(100))
    328350
    >>> i
    20

Test first class

    >>> g = (i*i for i in range(4))
    >>> type(g)
    <type 'generator'>
    >>> list(g)
    [0, 1, 4, 9]

Test direct calls to next()

    >>> g = (i*i for i in range(3))
    >>> g.next()
    0
    >>> g.next()
    1
    >>> g.next()
    4
    >>> g.next()
    Traceback (most recent call last):
      File "<pyshell#21>", line 1, in -toplevel-
        g.next()
    StopIteration

Does it stay stopped?

    >>> g.next()
    Traceback (most recent call last):
      File "<pyshell#21>", line 1, in -toplevel-
        g.next()
    StopIteration
    >>> list(g)
    []

Test running gen when defining function is out of scope

    >>> def f(n):
    ...     return (i*i for i in xrange(n))
    >>> list(f(10))
    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

    >>> def f(n):
    ...     return ((i,j) for i in xrange(3) for j in xrange(n))
    >>> list(f(4))
    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
    >>> def f(n):
    ...     return ((i,j) for i in xrange(3) for j in xrange(4) if j in xrange(n))
    >>> list(f(4))
    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]
    >>> list(f(2))
    [(0, 0), (0, 1), (1, 0), (1, 1), (2, 0), (2, 1)]

Verify that parenthesis are required in a statement

    >>> def f(n):
    ...     return i*i for i in xrange(n)
    Traceback (most recent call last):
       ...
    SyntaxError: invalid syntax

Verify that parenthesis are required when used as a keyword argument value

    >>> dict(a = i for i in xrange(10))
    Traceback (most recent call last):
       ...
    SyntaxError: invalid syntax

Verify that parenthesis are required when used as a keyword argument value

    >>> dict(a = (i for i in xrange(10))) #doctest: +ELLIPSIS
    {'a': <generator object at ...>}

Verify early binding for the outermost for-expression

    >>> x=10
    >>> g = (i*i for i in range(x))
    >>> x = 5
    >>> list(g)
    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Verify that the outermost for-expression makes an immediate check
for iterability

    >>> (i for i in 6)
    Traceback (most recent call last):
      File "<pyshell#4>", line 1, in -toplevel-
        (i for i in 6)
    TypeError: iteration over non-sequence

Verify late binding for the outermost if-expression

    >>> include = (2,4,6,8)
    >>> g = (i*i for i in range(10) if i in include)
    >>> include = (1,3,5,7,9)
    >>> list(g)
    [1, 9, 25, 49, 81]

Verify late binding for the innermost for-expression

    >>> g = ((i,j) for i in range(3) for j in range(x))
    >>> x = 4
    >>> list(g)
    [(0, 0), (0, 1), (0, 2), (0, 3), (1, 0), (1, 1), (1, 2), (1, 3), (2, 0), (2, 1), (2, 2), (2, 3)]

Verify re-use of tuples (a side benefit of using genexps over listcomps)

    >>> tupleids = map(id, ((i,i) for i in xrange(10)))
    >>> max(tupleids) - min(tupleids)
    0

Verify that syntax error's are raised for genexps used as lvalues

    >>> (y for y in (1,2)) = 10
    Traceback (most recent call last):
       ...
    SyntaxError: assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[40]>, line 1)

    >>> (y for y in (1,2)) += 10
    Traceback (most recent call last):
       ...
    SyntaxError: augmented assignment to generator expression not possible (<doctest test.test_genexps.__test__.doctests[41]>, line 1)


########### Tests borrowed from or inspired by test_generators.py ############

Make a generator that acts like range()

    >>> yrange = lambda n:  (i for i in xrange(n))
    >>> list(yrange(10))
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Generators always return to the most recent caller:

    >>> def creator():
    ...     r = yrange(5)
    ...     print "creator", r.next()
    ...     return r
    >>> def caller():
    ...     r = creator()
    ...     for i in r:
    ...             print "caller", i
    >>> caller()
    creator 0
    caller 1
    caller 2
    caller 3
    caller 4

Generators can call other generators:

    >>> def zrange(n):
    ...     for i in yrange(n):
    ...         yield i
    >>> list(zrange(5))
    [0, 1, 2, 3, 4]


Verify that a gen exp cannot be resumed while it is actively running:

    >>> g = (me.next() for i in xrange(10))
    >>> me = g
    >>> me.next()
    Traceback (most recent call last):
      File "<pyshell#30>", line 1, in -toplevel-
        me.next()
      File "<pyshell#28>", line 1, in <generator expression>
        g = (me.next() for i in xrange(10))
    ValueError: generator already executing

Verify exception propagation

    >>> g = (10 // i for i in (5, 0, 2))
    >>> g.next()
    2
    >>> g.next()
    Traceback (most recent call last):
      File "<pyshell#37>", line 1, in -toplevel-
        g.next()
      File "<pyshell#35>", line 1, in <generator expression>
        g = (10 // i for i in (5, 0, 2))
    ZeroDivisionError: integer division or modulo by zero
    >>> g.next()
    Traceback (most recent call last):
      File "<pyshell#38>", line 1, in -toplevel-
        g.next()
    StopIteration

Make sure that None is a valid return value

    >>> list(None for i in xrange(10))
    [None, None, None, None, None, None, None, None, None, None]

Check that generator attributes are present

    >>> g = (i*i for i in range(3))
    >>> expected = set(['gi_frame', 'gi_running', 'next'])
    >>> set(attr for attr in dir(g) if not attr.startswith('__')) >= expected
    True

    >>> print g.next.__doc__
    x.next() -> the next value, or raise StopIteration
    >>> import types
    >>> isinstance(g, types.GeneratorType)
    True

Check the __iter__ slot is defined to return self

    >>> iter(g) is g
    True

Verify that the running flag is set properly

    >>> g = (me.gi_running for i in (0,1))
    >>> me = g
    >>> me.gi_running
    0
    >>> me.next()
    1
    >>> me.gi_running
    0

Verify that genexps are weakly referencable

    >>> import weakref
    >>> g = (i*i for i in range(4))
    >>> wr = weakref.ref(g)
    >>> wr() is g
    True
    >>> p = weakref.proxy(g)
    >>> list(p)
    [0, 1, 4, 9]


"""


__test__ = {'doctests' : doctests}

def test_main(verbose=None):
    import sys
    from test import test_support
    from test import test_genexps
    test_support.run_doctest(test_genexps, verbose)

    # verify reference counting
    if verbose and hasattr(sys, "gettotalrefcount"):
        import gc
        counts = [None] * 5
        for i in xrange(len(counts)):
            test_support.run_doctest(test_genexps, verbose)
            gc.collect()
            counts[i] = sys.gettotalrefcount()
        print counts

if __name__ == "__main__":
    test_main(verbose=True)