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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        """Apply the given environment to the current process.
34
35        Args:
36            env (environment.Environment): Environment variables to use.
37            environ (dict): Where to set variables. In most cases this should be
38                os.environ.
39        """
40        self._unapply_steps = []
41        try:
42            self._environ = environ
43            env.accept(self)
44        finally:
45            self._environ = None
46
47    def visit_set(self, set):  # pylint: disable=redefined-builtin
48        self._environ[set.name] = set.value
49
50    def visit_clear(self, clear):
51        if clear.name in self._environ:
52            del self._environ[clear.name]
53
54    def visit_remove(self, remove):
55        values = self._environ.get(remove.name, '').split(self._pathsep)
56        norm = os.path.normpath
57        values = [x for x in values if norm(x) != norm(remove.value)]
58        self._environ[remove.name] = self._pathsep.join(values)
59
60    def visit_prepend(self, prepend):
61        self._environ[prepend.name] = self._pathsep.join(
62            (prepend.value, self._environ.get(prepend.name, ''))
63        )
64
65    def visit_append(self, append):
66        self._environ[append.name] = self._pathsep.join(
67            (self._environ.get(append.name, ''), append.value)
68        )
69
70    def visit_echo(self, echo):
71        pass  # Not relevant for apply.
72
73    def visit_comment(self, comment):
74        pass  # Not relevant for apply.
75
76    def visit_command(self, command):
77        pass  # Not relevant for apply.
78
79    def visit_doctor(self, doctor):
80        pass  # Not relevant for apply.
81
82    def visit_blank_line(self, blank_line):
83        pass  # Not relevant for apply.
84
85    def visit_function(self, function):
86        pass  # Not relevant for apply.
87
88    def visit_hash(self, hash):  # pylint: disable=redefined-builtin
89        pass  # Not relevant for apply.
90