python / python/cpython

importlib.resources.files() doesn't work correctly when importlib library is compiled

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stdlib topic-importlib type-bug
Dominant language
Python
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Description

Bug report

Bug description:

If importlib library is compiled (in particular _common.py), then any package, that uses bare files() to get its resources, breaks, because _infer_caller returns wrong frame (as mentioned in https://github.com/python/cpython/pull/123037#issuecomment-2294431430, __file__ in https://github.com/python/cpython/blob/35d8ac7cd7ed6cd3d84af721dce970da59bd5f68/Lib/importlib/resources/_common.py#L96 is not valid)

Reproducer:

import importlib
import os
import pathlib
import py_compile
import shutil
import sys
import tempfile
import textwrap


def compile(tempdir):
    target_dir = pathlib.Path(tempdir) / 'cimportlib'
    souce_dir = pathlib.Path(importlib.__file__).parent
    shutil.copytree(souce_dir, target_dir, ignore=lambda *_: ['__pycache__'])

    for dirpath, _, filenames in os.walk(target_dir):
        for filename in filenames:
            if filename != "_common.py":
                continue
            source_path = pathlib.Path(dirpath) / filename
            cfile = source_path.with_suffix('.pyc')
            py_compile.compile(source_path, cfile)
            pathlib.Path.unlink(source_path)


def create_package(tempdir):
    package_dir = pathlib.Path(tempdir) / 'somepkg'
    package_dir.mkdir()
    contents = {
        "__init__.py": textwrap.dedent(
            """
            import cimportlib.resources as res
            val = res.files().joinpath('resource.txt').read_text(encoding='utf-8')
            """
        ),
        "resource.txt": "data",
    }

    for file, content in contents.items():
        path = pathlib.Path(package_dir) / file
        path.write_text(content)


def main():
    with tempfile.TemporaryDirectory() as tempdir:
        compile(tempdir)
        create_package(tempdir)
        sys.path.insert(0, str(tempdir))
        print(importlib.import_module('somepkg').val)


if __name__ == "__main__":
    raise SystemExit(main())

Expectation:

data

Actual outcome:

FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpngnuw441/cimportlib/resources/resource.txt'

It may be important for frozen python applications, as they don't include source code

CPython versions tested on:

3.12, CPython main branch

Operating systems tested on:

Linux, Windows

Linked PRs
  • gh-123102
  • gh-124021
  • gh-124024
  • gh-124131
  • gh-128581
  • gh-128600
  • gh-137914

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with Lib/importlib/resources/_common.py, especially _infer_caller and the referenced line, then reproduce the failure with the supplied script using a compiled _common.py. Compare the expected data output with the FileNotFoundError; done means the reproducer works with compiled importlib without regressing normal resource loading.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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