Viewing file:  fix_raise.py (3.81 KB) -rw-r--r--
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"""Fixer for 'raise E, V'
From Armin Ronacher's ``python-modernize``.
raise -> raise
raise E -> raise E
raise E, 5 -> raise E(5)
raise E, 5, T -> raise E(5).with_traceback(T)
raise E, None, T -> raise E.with_traceback(T)
raise (((E, E'), E''), E'''), 5 -> raise E(5)
raise "foo", V, T -> warns about string exceptions
raise E, (V1, V2) -> raise E(V1, V2)
raise E, (V1, V2), T -> raise E(V1, V2).with_traceback(T)
CAVEATS:
1) "raise E, V, T" cannot be translated safely in general. If V
is not a tuple or a (number, string, None) literal, then:
raise E, V, T -> from future.utils import raise_
raise_(E, V, T)
"""
# Author: Collin Winter, Armin Ronacher, Mark Huang
# Local imports
from lib2to3 import pytree, fixer_base
from lib2to3.pgen2 import token
from lib2to3.fixer_util import Name, Call, is_tuple, Comma, Attr, ArgList
from libfuturize.fixer_util import touch_import_top
class FixRaise(fixer_base.BaseFix):
BM_compatible = True
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 == 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 "tb" in results:
tb = results["tb"].clone()
else:
tb = None
if "val" in results:
val = results["val"].clone()
if is_tuple(val):
# Assume that exc is a subclass of Exception and call exc(*val).
args = [c.clone() for c in val.children[1:-1]]
exc = Call(exc, args)
elif val.type in (token.NUMBER, token.STRING):
# Handle numeric and string literals specially, e.g.
# "raise Exception, 5" -> "raise Exception(5)".
val.prefix = u""
exc = Call(exc, [val])
elif val.type == token.NAME and val.value == u"None":
# Handle None specially, e.g.
# "raise Exception, None" -> "raise Exception".
pass
else:
# val is some other expression. If val evaluates to an instance
# of exc, it should just be raised. If val evaluates to None,
# a default instance of exc should be raised (as above). If val
# evaluates to a tuple, exc(*val) should be called (as
# above). Otherwise, exc(val) should be called. We can only
# tell what to do at runtime, so defer to future.utils.raise_(),
# which handles all of these cases.
touch_import_top(u"future.utils", u"raise_", node)
exc.prefix = u""
args = [exc, Comma(), val]
if tb is not None:
args += [Comma(), tb]
return Call(Name(u"raise_"), args, prefix=node.prefix)
if tb is not None:
tb.prefix = ""
exc_list = Attr(exc, Name('with_traceback')) + [ArgList([tb])]
else:
exc_list = [exc]
return pytree.Node(syms.raise_stmt,
[Name(u"raise")] + exc_list,
prefix=node.prefix)
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