[NANA6719]

Description

On Windows, SimpleDirectoryReader.load_data() failed with OSError: [Errno 22] Invalid argument when any file had a modification time before 1970, because datetime.fromtimestamp() does not accept negative timestamps there. The metadata is built outside the raise_on_error try block, so a single file made the whole call fail.

_format_file_timestamp() now catches OSError, OverflowError and ValueError and returns None. This follows the function's existing contract (it already returns None for a missing timestamp), and default_file_metadata_func() already drops None values, so only that date field is omitted and the file still loads. Other behavior is unchanged.

Fixes #23787

New Package?

• Yes
• No

Version Bump?

• Yes
• No (llama-index-core is exempt)

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• I added new unit tests to cover this change

• test__format_file_timestamp_out_of_range: inf, 1e20 and nan return None instead of raising. These values fail on every OS, so this test catches the bug on Linux CI too.

• test_SimpleDirectoryReader_pre_epoch_mtime: loads a real file whose mtime is set to 1969-12-31 and checks that the text and file_name metadata are kept. Before the fix it failed with OSError on Windows.

I confirmed that both new tests fail without the fix and pass with it. uv run -- pytest tests/readers/ passes (33 passed) on Windows 11 / Python 3.11.15, and pre-commit passes on the changed files.

AI Usage

I used Claude (an AI assistant) to help find this edge case, draft the fix and tests, and polish the English in this description. I reproduced the bug myself on Windows, checked for existing issues/PRs, reviewed every changed line, and ran the tests locally before and after the fix.

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran uv run make format; uv run make lint to appease the lint gods