1"""Fixer for 'raise E, V, T'
2
3raise         -> raise
4raise E       -> raise E
5raise E, V    -> raise E(V)
6raise E, V, T -> raise E(V).with_traceback(T)
7raise E, None, T -> raise E.with_traceback(T)
8
9raise (((E, E'), E''), E'''), V -> raise E(V)
10raise "foo", V, T               -> warns about string exceptions
11
12
13CAVEATS:
141) "raise E, V" will be incorrectly translated if V is an exception
15   instance. The correct Python 3 idiom is
16
17        raise E from V
18
19   but since we can't detect instance-hood by syntax alone and since
20   any client code would have to be changed as well, we don't automate
21   this.
22"""
23# Author: Collin Winter
24
25# Local imports
26from .. import pytree
27from ..pgen2 import token
28from .. import fixer_base
29from ..fixer_util import Name, Call, Attr, ArgList, is_tuple
30
31class FixRaise(fixer_base.BaseFix):
32
33    BM_compatible = True
34    PATTERN = """
35    raise_stmt< 'raise' exc=any [',' val=any [',' tb=any]] >
36    """
37
38    def transform(self, node, results):
39        syms = self.syms
40
41        exc = results["exc"].clone()
42        if exc.type == token.STRING:
43            msg = "Python 3 does not support string exceptions"
44            self.cannot_convert(node, msg)
45            return
46
47        # Python 2 supports
48        #  raise ((((E1, E2), E3), E4), E5), V
49        # as a synonym for
50        #  raise E1, V
51        # Since Python 3 will not support this, we recurse down any tuple
52        # literals, always taking the first element.
53        if is_tuple(exc):
54            while is_tuple(exc):
55                # exc.children[1:-1] is the unparenthesized tuple
56                # exc.children[1].children[0] is the first element of the tuple
57                exc = exc.children[1].children[0].clone()
58            exc.prefix = " "
59
60        if "val" not in results:
61            # One-argument raise
62            new = pytree.Node(syms.raise_stmt, [Name("raise"), exc])
63            new.prefix = node.prefix
64            return new
65
66        val = results["val"].clone()
67        if is_tuple(val):
68            args = [c.clone() for c in val.children[1:-1]]
69        else:
70            val.prefix = ""
71            args = [val]
72
73        if "tb" in results:
74            tb = results["tb"].clone()
75            tb.prefix = ""
76
77            e = exc
78            # If there's a traceback and None is passed as the value, then don't
79            # add a call, since the user probably just wants to add a
80            # traceback. See issue #9661.
81            if val.type != token.NAME or val.value != "None":
82                e = Call(exc, args)
83            with_tb = Attr(e, Name('with_traceback')) + [ArgList([tb])]
84            new = pytree.Node(syms.simple_stmt, [Name("raise")] + with_tb)
85            new.prefix = node.prefix
86            return new
87        else:
88            return pytree.Node(syms.raise_stmt,
89                               [Name("raise"), Call(exc, args)],
90                               prefix=node.prefix)
91