lifted molecule code to add env var support (#39)

* lifted molecule code to add env var support

* made include consistent & improved doc string

* fix test name

gilt/config.py

@@ -27,6 +27,8 @@
 import giturlparse
 import yaml
 
+from gilt import interpolation
+
 
 class ParseError(Exception):
  """ Error raised when a config can't be loaded properly. """
@@ -128,9 +130,13 @@ def _get_config(filename):
  :parse filename: A string containing the path to YAML file.
  :return: dict
  """
+ i = interpolation.Interpolator(interpolation.TemplateWithDefaults,
+ os.environ)
+
  with open(filename, 'r') as stream:
  try:
- return yaml.safe_load(stream)
+ interpolated_config = i.interpolate(stream.read())
+ return yaml.safe_load(interpolated_config)
  except yaml.parser.ParserError as e:
  msg = 'Error parsing gilt config: {0}'.format(e)
  raise ParseError(msg)

gilt/interpolation.py

@@ -0,0 +1,81 @@
+# 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:https://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 `ETCD_VERSION=1.0` and the following
+ gilt.yml is supplied.
+ .. code-block:: yaml
+ - git: https://github.com/retr0h/ansible-etcd.git
+ version: ${ETCD_VERSION}
+ dst: roles/retr0h.ansible-etcd-${ETCD_VERSION}/
+ will substitute `${ETCD_VERSION}` with the value of the
+ `ETCD_VERSION` environment variable.
+ .. warning::
+ If an environment variable is not set, gilt substitutes with an
+ empty string.
+ Both `$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)

test/test_interpolation.py

@@ -0,0 +1,89 @@
+# 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:https://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.
+
+import pytest
+
+from gilt import interpolation
+
+
+@pytest.fixture
+def mock_env():
+ return {'FOO': 'foo', 'BAR': '', 'ETCD_VERSION': 'master'}
+
+
+@pytest.fixture
+def interpolator_instance(mock_env):
+ return interpolation.Interpolator(interpolation.TemplateWithDefaults,
+ mock_env).interpolate
+
+
+def test_escaped_interpolation(interpolator_instance):
+ assert '${foo}' == interpolator_instance('$${foo}')
+
+
+def test_invalid_interpolation(interpolator_instance):
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('$}')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${}')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${ }')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${ foo}')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${foo }')
+ with pytest.raises(interpolation.InvalidInterpolation):
+ interpolator_instance('${foo!}')
+
+
+def test_interpolate_missing_no_default(interpolator_instance):
+ assert 'This var' == interpolator_instance('This ${missing} var')
+ assert 'This var' == interpolator_instance('This ${BAR} var')
+
+
+def test_interpolate_with_value(interpolator_instance):
+ assert 'This foo var' == interpolator_instance('This $FOO var')
+ assert 'This foo var' == interpolator_instance('This ${FOO} var')
+
+
+def test_interpolate_missing_with_default(interpolator_instance):
+ assert 'ok def' == interpolator_instance('ok ${missing:-def}')
+ assert 'ok def' == interpolator_instance('ok ${missing-def}')
+ assert 'ok /non:-alphanumeric' == interpolator_instance(
+ 'ok ${BAR:-/non:-alphanumeric}')
+
+
+def test_interpolate_with_empty_and_default_value(interpolator_instance):
+ assert 'ok def' == interpolator_instance('ok ${BAR:-def}')
+ assert 'ok ' == interpolator_instance('ok ${BAR-def}')
+
+
+def test_interpolate_with_gilt_yaml(interpolator_instance):
+ data = """
+---
+ git: [email protected]:retr0h/ansible-etcd.git
+ version: ${ETCD_VERSION}
+ dst: roles/etcd-$ETCD_VERSION
+""".strip()
+
+ x = """
+---
+ git: [email protected]:retr0h/ansible-etcd.git
+ version: master
+ dst: roles/etcd-master
+""".strip()
+
+ assert x == interpolator_instance(data)