1# Copyright 2007 Google, Inc. All Rights Reserved.
2# Licensed to PSF under a Contributor Agreement.
3
4"""Fixer that changes map(F, ...) into list(map(F, ...)) unless there
5exists a 'from future_builtins import map' statement in the top-level
6namespace.
7
8As a special case, map(None, X) is changed into list(X).  (This is
9necessary because the semantics are changed in this case -- the new
10map(None, X) is equivalent to [(x,) for x in X].)
11
12We avoid the transformation (except for the special case mentioned
13above) if the map() call is directly contained in iter(<>), list(<>),
14tuple(<>), sorted(<>), ...join(<>), or for V in <>:.
15
16NOTE: This is still not correct if the original code was depending on
17map(F, X, Y, ...) to go on until the longest argument is exhausted,
18substituting None for missing values -- like zip(), it now stops as
19soon as the shortest argument is exhausted.
20"""
21
22# Local imports
23from ..pgen2 import token
24from .. import fixer_base
25from ..fixer_util import Name, ArgList, Call, ListComp, in_special_context
26from ..pygram import python_symbols as syms
27from ..pytree import Node
28
29
30class FixMap(fixer_base.ConditionalFix):
31    BM_compatible = True
32
33    PATTERN = """
34    map_none=power<
35        'map'
36        trailer< '(' arglist< 'None' ',' arg=any [','] > ')' >
37        [extra_trailers=trailer*]
38    >
39    |
40    map_lambda=power<
41        'map'
42        trailer<
43            '('
44            arglist<
45                lambdef< 'lambda'
46                         (fp=NAME | vfpdef< '(' fp=NAME ')'> ) ':' xp=any
47                >
48                ','
49                it=any
50            >
51            ')'
52        >
53        [extra_trailers=trailer*]
54    >
55    |
56    power<
57        'map' args=trailer< '(' [any] ')' >
58        [extra_trailers=trailer*]
59    >
60    """
61
62    skip_on = 'future_builtins.map'
63
64    def transform(self, node, results):
65        if self.should_skip(node):
66            return
67
68        trailers = []
69        if 'extra_trailers' in results:
70            for t in results['extra_trailers']:
71                trailers.append(t.clone())
72
73        if node.parent.type == syms.simple_stmt:
74            self.warning(node, "You should use a for loop here")
75            new = node.clone()
76            new.prefix = ""
77            new = Call(Name("list"), [new])
78        elif "map_lambda" in results:
79            new = ListComp(results["xp"].clone(),
80                           results["fp"].clone(),
81                           results["it"].clone())
82            new = Node(syms.power, [new] + trailers, prefix="")
83
84        else:
85            if "map_none" in results:
86                new = results["arg"].clone()
87                new.prefix = ""
88            else:
89                if "args" in results:
90                    args = results["args"]
91                    if args.type == syms.trailer and \
92                       args.children[1].type == syms.arglist and \
93                       args.children[1].children[0].type == token.NAME and \
94                       args.children[1].children[0].value == "None":
95                        self.warning(node, "cannot convert map(None, ...) "
96                                     "with multiple arguments because map() "
97                                     "now truncates to the shortest sequence")
98                        return
99
100                    new = Node(syms.power, [Name("map"), args.clone()])
101                    new.prefix = ""
102
103                if in_special_context(node):
104                    return None
105
106            new = Node(syms.power, [Name("list"), ArgList([new])] + trailers)
107            new.prefix = ""
108
109        new.prefix = node.prefix
110        return new
111