Add support of symbolic links as entrypoint of function.

[ohtanim]

Summary

If the entrypoint specified in Function is not a regular file but a symbolic link to a python file, the upload to the cluster will be incomplete and execution of the entrypoint will fail. This PR provides support to run with symbolic links/hardlinks in addition to real file.

Details and comments

Creates source_files directory and put the following 2 files. One is real file, another is symbolic linked file.

source_files/
    pattern_with_arguments.py@ -> ../basic/source_files/pattern_with_arguments.py

And then, creates an instance of QiskitFunction with pattern_with_parallel_workflow.py as entrypoint.

function = QiskitFunction(
    title="test",
    entrypoint="pattern_with_parallel_workflow.py",
    working_dir="./source_files/",
)

Above invocation and subsequent upload() are succeeded, but the following error is occurred when running this function.

2024-10-11 12:48:18,794	INFO job_manager.py:531 -- Runtime env is setting up.
python: can't open file '/tmp/ray/session_2024-10-11_12-05-19_925458_1/runtime_resources/working_dir_files/_ray_pkg_e8408231f4c60cc4/pattern_with_parallel_workflow.py': [Errno 2] No such file or directory

This is because of this implementation.

Symbolic link target(=content) will not be included in the archive file. As result, it will not be available in the cluster side.
TarFile provides the solution for this case. The content of the target files can be added to the archive if dereference=True.



with tarfile.open(artifact_file_path, "w", dereference=True) as tar:

This PR will change above 1 line to support both regular file and symbolic/hard links.

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[akihikokuroda]

LGTM!

[akihikokuroda]

@ohtanim Thanks for your contributions! It's a good catch. We probably need to add a test for it. @Tansito

[psschwei]

Nice catch!