BUG: Guard empty input to prevent IndexError

[KyleJung0828]

Resolves #3446

How to check

As mentioned in #3446 you can test with guwunmong.pdf.

>>> import os
>>> from io import BytesIO
>>> from pypdf import PdfReader
>>> with open("guwunmong.pdf", "rb") as f:
...     pdf_bytes = f.read()
>>> reader = PdfReader(stream=BytesIO(pdf_bytes))
>>> metadata = reader.metadata
>>> creation_date = str(metadata.creation_date) if metadata.creation_date else None  # Used to raise IndexError here.
>>> creation_date
>>> print(creation_date)  # Prints None as expected.
None

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.97%. Comparing base (bc318d7) to head (415b04b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3448   +/-   ##
=======================================
  Coverage   96.97%   96.97%           
=======================================
  Files          54       54           
  Lines        9337     9337           
  Branches     1711     1711           
=======================================
  Hits         9055     9055           
  Misses        168      168           
  Partials      114      114           

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[stefan6419846]

Thanks for the PR. Could you please add a corresponding test as well?

[KyleJung0828]

@stefan6419846
Sure. Do I just write a simple test function that tests text='' case, similar to what test_parse_datetime_err does? (No need to add guwunmong.pdf to sample-files repo?)

[stefan6419846]

You can either add a unit test without a PDF file or an integration test with downloading the PDF file on the fly (see other tests). If possible, I consider a unit test suitable enough here.

[KyleJung0828]

@stefan6419846
I added a simple unit test for edge cases like "" and None as inputs (I rebased and squashed with the old commit for history). Let me know if something needs to be changed.

[stefan6419846]

Thanks.