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# Copyright 2014-2015 Canonical Limited.
#
# 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.
import os
import sys
from charmhelpers.core import host
from charmhelpers.core import hookenv
def render(source, target, context, owner='root', group='root',
perms=0o444, templates_dir=None, encoding='UTF-8', template_loader=None):
"""
Render a template.
The `source` path, if not absolute, is relative to the `templates_dir`.
The `target` path should be absolute. It can also be `None`, in which
case no file will be written.
The context should be a dict containing the values to be replaced in the
template.
The `owner`, `group`, and `perms` options will be passed to `write_file`.
If omitted, `templates_dir` defaults to the `templates` folder in the charm.
The rendered template will be written to the file as well as being returned
as a string.
Note: Using this requires python-jinja2 or python3-jinja2; if it is not
installed, calling this will attempt to use charmhelpers.fetch.apt_install
to install it.
"""
try:
from jinja2 import FileSystemLoader, Environment, exceptions
except ImportError:
try:
from charmhelpers.fetch import apt_install
except ImportError:
hookenv.log('Could not import jinja2, and could not import '
'charmhelpers.fetch to install it',
level=hookenv.ERROR)
raise
if sys.version_info.major == 2:
apt_install('python-jinja2', fatal=True)
else:
apt_install('python3-jinja2', fatal=True)
from jinja2 import FileSystemLoader, Environment, exceptions
if template_loader:
template_env = Environment(loader=template_loader)
else:
if templates_dir is None:
templates_dir = os.path.join(hookenv.charm_dir(), 'templates')
template_env = Environment(loader=FileSystemLoader(templates_dir))
try:
source = source
template = template_env.get_template(source)
except exceptions.TemplateNotFound as e:
hookenv.log('Could not load template %s from %s.' %
(source, templates_dir),
level=hookenv.ERROR)
raise e
content = template.render(context)
if target is not None:
target_dir = os.path.dirname(target)
if not os.path.exists(target_dir):
# This is a terrible default directory permission, as the file
# or its siblings will often contain secrets.
host.mkdir(os.path.dirname(target), owner, group, perms=0o755)
host.write_file(target, content.encode(encoding), owner, group, perms)
return content
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