"""Jinja2 environment and extensions loading."""
from jinja2 import Environment, StrictUndefined
from cookiecutter.exceptions import UnknownExtension
[docs]class ExtensionLoaderMixin(object):
"""Mixin providing sane loading of extensions specified in a given context.
The context is being extracted from the keyword arguments before calling
the next parent class in line of the child.
"""
def __init__(self, **kwargs):
"""Initialize the Jinja2 Environment object while loading extensions.
Does the following:
1. Establishes default_extensions (currently just a Time feature)
2. Reads extensions set in the cookiecutter.json _extensions key.
3. Attempts to load the extensions. Provides useful error if fails.
"""
context = kwargs.pop('context', {})
default_extensions = [
'cookiecutter.extensions.JsonifyExtension',
'cookiecutter.extensions.RandomStringExtension',
'cookiecutter.extensions.SlugifyExtension',
'cookiecutter.extensions.UUIDExtension',
'jinja2_time.TimeExtension',
]
extensions = default_extensions + self._read_extensions(context)
try:
super(ExtensionLoaderMixin, self).__init__(extensions=extensions, **kwargs)
except ImportError as err:
raise UnknownExtension('Unable to load extension: {}'.format(err))
def _read_extensions(self, context):
"""Return list of extensions as str to be passed on to the Jinja2 env.
If context does not contain the relevant info, return an empty
list instead.
"""
try:
extensions = context['cookiecutter']['_extensions']
except KeyError:
return []
else:
return [str(ext) for ext in extensions]
[docs]class StrictEnvironment(ExtensionLoaderMixin, Environment):
"""Create strict Jinja2 environment.
Jinja2 environment will raise error on undefined variable in template-
rendering context.
"""
def __init__(self, **kwargs):
"""Set the standard Cookiecutter StrictEnvironment.
Also loading extensions defined in cookiecutter.json's _extensions key.
"""
super(StrictEnvironment, self).__init__(undefined=StrictUndefined, **kwargs)