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1# Copyright 2021 The Pigweed Authors
2#
3# Licensed under the Apache License, Version 2.0 (the "License"); you may not
4# use this file except in compliance with the License. You may obtain a copy of
5# the License at
6#
7#     https://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12# License for the specific language governing permissions and limitations under
13# the License.
14"""Applies an Environment to the current process."""
15
16import os
17
18# Disable super() warnings since this file must be Python 2 compatible.
19# pylint: disable=super-with-arguments
20
21
22class ApplyVisitor(object):  # pylint: disable=useless-object-inheritance
23    """Applies an Environment to the current process."""
24
25    def __init__(self, *args, **kwargs):
26        pathsep = kwargs.pop('pathsep', os.pathsep)
27        super(ApplyVisitor, self).__init__(*args, **kwargs)
28        self._pathsep = pathsep
29        self._environ = None
30        self._unapply_steps = None
31
32    def apply(self, env, environ):
33        self._unapply_steps = []
34        try:
35            self._environ = environ
36            env.accept(self)
37        finally:
38            self._environ = None
39
40    def visit_set(self, set):  # pylint: disable=redefined-builtin
41        self._environ[set.name] = set.value
42
43    def visit_clear(self, clear):
44        if clear.name in self._environ:
45            del self._environ[clear.name]
46
47    def visit_remove(self, remove):
48        values = self._environ.get(remove.name, '').split(self._pathsep)
49        norm = os.path.normpath
50        values = [x for x in values if norm(x) != norm(remove.value)]
51        self._environ[remove.name] = self._pathsep.join(values)
52
53    def visit_prepend(self, prepend):
54        self._environ[prepend.name] = self._pathsep.join(
55            (prepend.value, self._environ.get(prepend.name, ''))
56        )
57
58    def visit_append(self, append):
59        self._environ[append.name] = self._pathsep.join(
60            (self._environ.get(append.name, ''), append.value)
61        )
62
63    def visit_echo(self, echo):
64        pass  # Not relevant for apply.
65
66    def visit_comment(self, comment):
67        pass  # Not relevant for apply.
68
69    def visit_command(self, command):
70        pass  # Not relevant for apply.
71
72    def visit_doctor(self, doctor):
73        pass  # Not relevant for apply.
74
75    def visit_blank_line(self, blank_line):
76        pass  # Not relevant for apply.
77
78    def visit_function(self, function):
79        pass  # Not relevant for apply.
80
81    def visit_hash(self, hash):  # pylint: disable=redefined-builtin
82        pass  # Not relevant for apply.
83