Replace pkg_resource by importlib_resources

[gsemet]

Hi.

Can you provide a future-proof loader that use importlib_resources instead of pkg_resource, which does not work pretty well in every case (on my pyinstaller package for instance it fails).

For me the use of pkg_resource should be avoided, it is about to be discarded (or maybe one day setuptools will not embed it). Providing a loader compatible with importlib_resources (the backport that brings' 3.7 importlib.resources to Python <3.7) is the easiest and more future-proof solution.

Thanks

[ThiefMaster]

Sounds like a good first contribution :)

[gsemet]

Working on it, but I do not garantee anything.

For information, they have a migration guide.

[gsemet]

So here is my resource loader I have developped for my simple use case (works fine):

# coding: utf-8

"""
A Jinja template loader using Importlib_resource.
"""

# Third Party Libraries
import importlib_resources
from jinja2.exceptions import TemplateNotFound
from jinja2.loaders import BaseLoader
from jinja2.loaders import split_template_path


class ImportLibResourceLoader(BaseLoader):
    # Adapted from PackageResource, using this migration guide:
    # https://importlib-resources.readthedocs.io/en/latest/migration.html#migration

    def __init__(self, templates_path, encoding='utf-8'):
        self.templates_path = templates_path
        self.encoding = encoding

    def get_source(self, environment, template):
        pieces = split_template_path(template)
        p = '/'.join((self.templates_path, ) + tuple(pieces))
        if not self._has_resource(p):
            raise TemplateNotFound(template)

        package_name, _, filename = p.rpartition("/")
        source = importlib_resources.read_binary(package_name, filename)

        def uptodate():
            return False

        return source.decode(self.encoding), filename, uptodate

    def list_templates(self):
        path = self.templates_path
        if path[:2] == './':
            path = path[2:]
        elif path == '.':
            path = ''
        offset = len(path)
        results = []

        def _walk(path):
            for filename in importlib_resources.contents(path):
                fullname = path + '/' + filename
                if self._is_dir(path, filename):
                    _walk(fullname)
                else:
                    results.append(fullname[offset:].lstrip('/'))

        _walk(path)
        results.sort()
        return results

    def _is_dir(self, templates_path: str, wanted_resource: str) -> bool:
        return (wanted_resource in importlib_resources.contents(templates_path) and
                not importlib_resources.is_resource(templates_path,
                                                    wanted_resource))

    def _has_resource(self, resource_path: str) -> bool:
        dir_name, _, filename = resource_path.rpartition("/")
        return filename in importlib_resources.contents(dir_name)

[davidism]

Reverting this in 2.11.2, it broke compatibility with Pytest. However, support will be present when 3.0 is released. See #1168, #1169