from jinja2 import BaseLoader, Environment, FileSystemLoader, TemplateError

import os

from constructor.exceptions import UnableToParse

# adapted from conda-build

class FilteredLoader(BaseLoader):

"""

A pass-through for the given loader, except that the loaded source is

filtered according to any metadata selectors in the source text.

"""

def __init__(self, unfiltered_loader, content_filter):

self._unfiltered_loader = unfiltered_loader

self.list_templates = unfiltered_loader.list_templates

self.content_filter = content_filter

def get_source(self, environment, template):

loader = self._unfiltered_loader

contents, filename, uptodate = loader.get_source(environment, template)

filtered_contents = self.content_filter(contents)

return filtered_contents, filename, uptodate

# adapted from conda-build

def render_jinja(data, directory, content_filter):

loader = FilteredLoader(FileSystemLoader(directory), content_filter)

env = Environment(loader=loader)

env.globals['environ'] = os.environ.copy()

env.globals['os'] = os

try:

template = env.from_string(data)

rendered = template.render()

except TemplateError as ex:

raise UnableToParse(original=ex)

return rendered