1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
# copyright 2003-2015 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of astroid.
#
# astroid is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# astroid is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with astroid. If not, see <http://www.gnu.org/licenses/>.
import collections
import warnings
class TransformVisitor(object):
"""A visitor for handling transforms.
The standard approach of using it is to call
:meth:`~visit` with an *astroid* module and the class
will take care of the rest, walking the tree and running the
transforms for each encountered node.
"""
def __init__(self):
self.transforms = collections.defaultdict(list)
def _transform(self, node):
"""Call matching transforms for the given node if any and return the
transformed node.
"""
cls = node.__class__
if cls not in self.transforms:
# no transform registered for this class of node
return node
transforms = self.transforms[cls]
orig_node = node # copy the reference
for transform_func, predicate in transforms:
if predicate is None or predicate(node):
ret = transform_func(node)
# if the transformation function returns something, it's
# expected to be a replacement for the node
if ret is not None:
if node is not orig_node:
# node has already be modified by some previous
# transformation, warn about it
warnings.warn('node %s substituted multiple times' % node)
node = ret
return node
def _visit(self, node):
if hasattr(node, '_astroid_fields'):
for field in node._astroid_fields:
value = getattr(node, field)
visited = self._visit_generic(value)
setattr(node, field, visited)
return self._transform(node)
def _visit_generic(self, node):
if isinstance(node, list):
return [self._visit_generic(child) for child in node]
elif isinstance(node, tuple):
return tuple(self._visit_generic(child) for child in node)
else:
return self._visit(node)
def register_transform(self, node_class, transform, predicate=None):
"""Register `transform(node)` function to be applied on the given
astroid's `node_class` if `predicate` is None or returns true
when called with the node as argument.
The transform function may return a value which is then used to
substitute the original node in the tree.
"""
self.transforms[node_class].append((transform, predicate))
def unregister_transform(self, node_class, transform, predicate=None):
"""Unregister the given transform."""
self.transforms[node_class].remove((transform, predicate))
def visit(self, module):
"""Walk the given astroid *tree* and transform each encountered node
Only the nodes which have transforms registered will actually
be replaced or changed.
"""
module.body = [self._visit(child) for child in module.body]
return self._transform(module)
|
