I was trying to use the PackageLoader to load template files from a package.

env = jinja2.Environment(
    autoescape=False,
    loader=jinja2.PackageLoader("testpkg", ""),
    trim_blocks=True,
    lstrip_blocks=True,
    keep_trailing_newline=True,
    undefined=jinja2.StrictUndefined
)
template = env.get_template("template-file.txt.in")

This works fine during development, but after packaging the module into an .egg file, it fails to load the file with:

Traceback (most recent call last):
  File "<frozen zipimport>", line 177, in get_data
KeyError: 'testpkg/./template-file.txt.in'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/miniconda3/envs/pyenv/lib/python3.9/site-packages/jinja2/loaders.py", line 338, in get_source
    source = self._loader.get_data(p)  # type: ignore
  File "<frozen zipimport>", line 179, in get_data
OSError: [Errno 0] : 'testpkg/./template-file.txt.in'

Environment:

• Python version: Python 3.9.4
• Jinja version: 3.0.1

Cause:

Inside ZIP files, the . (for current directory) is an invalid path, thus it fails to find the file.

The PackageLoader actually tries to remove the dot from the path, here:

Calling normpath first and cleaning the path afterwards (273..276) should fix the bug.
Alternatively one could normalize the path again after the join in