1 """Fixer for 'raise E, V, T'

     2 

     3 raise         -> raise

     4 raise E       -> raise E

     5 raise E, V    -> raise E(V)

     6 raise E, V, T -> raise E(V).with_traceback(T)

     7 

     8 raise (((E, E'), E''), E'''), V -> raise E(V)

     9 raise "foo", V, T               -> warns about string exceptions

    10 

    11 

    12 CAVEATS:

    13 1) "raise E, V" will be incorrectly translated if V is an exception

    14    instance. The correct Python 3 idiom is

    15 

    16         raise E from V

    17 

    18    but since we can't detect instance-hood by syntax alone and since

    19    any client code would have to be changed as well, we don't automate

    20    this.

    21 """

    22 # Author: Collin Winter

    23 

    24 # Local imports

    25 from .. import pytree

    26 from ..pgen2 import token

    27 from .. import fixer_base

    28 from ..fixer_util import Name, Call, Attr, ArgList, is_tuple

    29 

    30 class FixRaise(fixer_base.BaseFix):

    31 

    32     PATTERN = """

    33     raise_stmt< 'raise' exc=any [',' val=any [',' tb=any]] >

    34     """

    35 

    36     def transform(self, node, results):

    37         syms = self.syms

    38 

    39         exc = results["exc"].clone()

    40         if exc.type is token.STRING:

    41             self.cannot_convert(node, "Python 3 does not support string exceptions")

    42             return

    43 

    44         # Python 2 supports

    45         #  raise ((((E1, E2), E3), E4), E5), V

    46         # as a synonym for

    47         #  raise E1, V

    48         # Since Python 3 will not support this, we recurse down any tuple

    49         # literals, always taking the first element.

    50         if is_tuple(exc):

    51             while is_tuple(exc):

    52                 # exc.children[1:-1] is the unparenthesized tuple

    53                 # exc.children[1].children[0] is the first element of the tuple

    54                 exc = exc.children[1].children[0].clone()

    55             exc.set_prefix(" ")

    56 

    57         if "val" not in results:

    58             # One-argument raise

    59             new = pytree.Node(syms.raise_stmt, [Name("raise"), exc])

    60             new.set_prefix(node.get_prefix())

    61             return new

    62 

    63         val = results["val"].clone()

    64         if is_tuple(val):

    65             args = [c.clone() for c in val.children[1:-1]]

    66         else:

    67             val.set_prefix("")

    68             args = [val]

    69 

    70         if "tb" in results:

    71             tb = results["tb"].clone()

    72             tb.set_prefix("")

    73 

    74             e = Call(exc, args)

    75             with_tb = Attr(e, Name('with_traceback')) + [ArgList([tb])]

    76             new = pytree.Node(syms.simple_stmt, [Name("raise")] + with_tb)

    77             new.set_prefix(node.get_prefix())

    78             return new

    79         else:

    80             return pytree.Node(syms.raise_stmt,

    81                                [Name("raise"), Call(exc, args)],

    82                                prefix=node.get_prefix())