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"""Fixer for 'raise E, V, T'
raise -> raise
raise E -> raise E
raise E, V -> raise E(V)
raise E, V, T -> raise E(V).with_traceback(T)
raise (((E, E'), E''), E'''), V -> raise E(V)
raise "foo", V, T -> warns about string exceptions
CAVEATS:
1) "raise E, V" will be incorrectly translated if V is an exception
instance. The correct Python 3 idiom is
raise E from V
but since we can't detect instance-hood by syntax alone and since
any client code would have to be changed as well, we don't automate
this.
"""
# Author: Collin Winter
# Local imports
from .. import pytree
from ..pgen2 import token
from .. import fixer_base
from ..fixer_util import Name, Call, Attr, ArgList, is_tuple
class FixRaise(fixer_base.BaseFix):
PATTERN = """
raise_stmt< 'raise' exc=any [',' val=any [',' tb=any]] >
"""
def transform(self, node, results):
syms = self.syms
exc = results["exc"].clone()
if exc.type is token.STRING:
self.cannot_convert(node, "Python 3 does not support string exceptions")
return
# Python 2 supports
# raise ((((E1, E2), E3), E4), E5), V
# as a synonym for
# raise E1, V
# Since Python 3 will not support this, we recurse down any tuple
# literals, always taking the first element.
if is_tuple(exc):
while is_tuple(exc):
# exc.children[1:-1] is the unparenthesized tuple
# exc.children[1].children[0] is the first element of the tuple
exc = exc.children[1].children[0].clone()
exc.prefix = " "
if "val" not in results:
# One-argument raise
new = pytree.Node(syms.raise_stmt, [Name(u"raise"), exc])
new.prefix = node.prefix
return new
val = results["val"].clone()
if is_tuple(val):
args = [c.clone() for c in val.children[1:-1]]
else:
val.prefix = u""
args = [val]
if "tb" in results:
tb = results["tb"].clone()
tb.prefix = u""
e = Call(exc, args)
with_tb = Attr(e, Name(u'with_traceback')) + [ArgList([tb])]
new = pytree.Node(syms.simple_stmt, [Name(u"raise")] + with_tb)
new.prefix = node.prefix
return new
else:
return pytree.Node(syms.raise_stmt,
[Name(u"raise"), Call(exc, args)],
prefix=node.prefix)