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interpolation.py
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interpolation.py
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# Copyright 2015 Docker, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
# Taken from Docker Compose:
# https://github.com/docker/compose/blob/master/compose/config/interpolation.py
import string
class InvalidInterpolation(Exception):
def __init__(self, string):
self.string = string
class Interpolator(object):
"""
Configuration options may contain environment variables. For example,
suppose the shell contains `VERIFIER_NAME=testinfra` and the following
molecule.yml is supplied.
.. code-block:: yaml
verifier:
- name: ${VERIFIER_NAME}
Molecule will substitute `$VERIFIER_NAME` with the value of the
`VERIFIER_NAME` environment variable.
.. warning::
If an environment variable is not set, Molecule substitutes with an
empty string.
Both `$VARIABLE` and `${VARIABLE}` syntax are supported. Extended
shell-style features, such as `${VARIABLE-default}` and
`${VARIABLE:-default}` are also supported.
If a literal dollar sign is needed in a configuration, use a double dollar
sign (`$$`).
"""
def __init__(self, templater, mapping):
self.templater = templater
self.mapping = mapping
def interpolate(self, string):
try:
return self.templater(string).substitute(self.mapping)
except ValueError:
raise InvalidInterpolation(string)
class TemplateWithDefaults(string.Template):
idpattern = r'[_a-z][_a-z0-9]*(?::?-[^}]+)?'
# Modified from python2.7/string.py
def substitute(self, mapping):
# Helper function for .sub()
def convert(mo):
# Check the most common path first.
named = mo.group('named') or mo.group('braced')
if named is not None:
if ':-' in named:
var, _, default = named.partition(':-')
return mapping.get(var) or default
if '-' in named:
var, _, default = named.partition('-')
return mapping.get(var, default)
val = mapping.get(named, '')
return '%s' % (val, )
if mo.group('escaped') is not None:
return self.delimiter
if mo.group('invalid') is not None:
self._invalid(mo)
return self.pattern.sub(convert, self.template)