[INFRAHELP-2899] fix: address race condition in load_nested_zip() and add tests

[ajaxbits]

Fixes a race condition in nested_zip_loader where, if multiple processes are trying to run load_nested_zip() a race condition could occur. Two processes would try to call os.rename at the same time, which would fail if the target_package_path was not empty.

To get around this, we create a filesystem lockfile. Each time load_nested_zip() runs, it has to acquire the lock, ensuring that concurrent unzips are impossible.

A basic set of tests are also added to assert this behavior. It tests that cold starts always extract, warm starts skip the extraction step, nothing is left behind, and that multiple processes running at the same time don't create a race condition.

Note

We have to use importlib in the tests because nested_zip_loader.py calls load_nested_zip() at import time. This is essential to its function and can't be worked around. Therefore, we have to do some shenanigans with importlib to be able to actually test load_nested_zip() in isolation on test data.

Finally, we fix a small bug where we never explicitly closed zipfile.ZipFile.

[Copilot]

Pull request overview

This PR addresses a reported race condition in package_python_function/nested_zip_loader.py by serializing extraction/rename with a filesystem lock, and introduces a focused test suite to validate cold-start/warm-start behavior and concurrent imports.

Changes:

• Add an fcntl.flock-based lockfile around nested dependency extraction/rename to prevent concurrent processes from racing.
• Add tests/test_nested_zip_loader.py to validate extraction behavior, staging cleanup, and a basic multi-process concurrency scenario.
• Remove the prior packaging/CLI test suite (tests/test_package_python_function.py, tests/conftest.py, tests/test_local.py) and add .opencode to .gitignore.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
package_python_function/nested_zip_loader.py	Adds a lockfile to avoid concurrent extraction/rename races; minor formatting changes.
tests/test_nested_zip_loader.py	New unit tests for loader cold/warm starts, staging cleanup, and concurrency.
tests/test_package_python_function.py	Removed (previous end-to-end packaging/reproducibility tests).
tests/conftest.py	Removed (previous shared test data/fixtures for packaging tests).
tests/test_local.py	Removed (previous local/manual test helper).
.gitignore	Ignores .opencode.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

[BrandonLWhite]

Looks like a very good solution to the problem. Thanks!