"""Fixer for 'raise E, V'
From Armin Ronacher's ``python-modernize``.
raise -> raise
raise E -> raise E
raise E, V -> raise E(V)
raise (((E, E'), E''), E'''), V -> raise E(V)
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, Armin Ronacher
# Local imports
from lib2to3 import pytree, fixer_base
from lib2to3.pgen2 import token
from lib2to3.fixer_util import Name, Call, is_tuple
class FixRaise(fixer_base.BaseFix):
BM_compatible = True
PATTERN = """
raise_stmt< 'raise' exc=any [',' val=any] >
"""
def transform(self, node, results):
syms = self.syms
exc = results["exc"].clone()
if exc.type == token.STRING:
msg = "Python 3 does not support string exceptions"
self.cannot_convert(node, msg)
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 = u" "
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]
return pytree.Node(syms.raise_stmt,
[Name(u"raise"), Call(exc, args)],
prefix=node.prefix)
