BUG: fix empty suffix and prefix handling in pyarrow string methods

[vkverma9534]

Python's str.removeprefix("") and str.removesuffix("") return the original string.

The current pyarrow-backed implementation slices with stop=0 or start=0 when the prefix or suffix is empty, which can result in unexpected behavior instead of preserving the original values.

This PR adds explicit guards for empty prefix and suffix inputs and includes tests to ensure parity with Python semantics.

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.
• If I used AI to develop this pull request, I prompted it to follow AGENTS.md.

[jorisvandenbossche]

@vkverma9534 Thanks for the catch and for the PR!

Could you add a test for this case? There is an existing test test_removeprefix/test_removesuffix in pandas/tests/strings/test_strings.py, where I think you can simply add one more case to the parametrize cases.

[vkverma9534]

Added explicit handling for empty prefix and suffix and added regression tests.

[vkverma9534]

The Locale: it_IT failure appears to be due to an apt-get update error:
Microsoft’s Ubuntu repo (packages.microsoft.com) returns 403, causing the job to exit before tests run.
I didn’t change CI or system dependencies, but I’m happy to rerun or adjust if needed.

[jorisvandenbossche]

The Locale: it_IT failure appears to be due to an apt-get update error:
Microsoft’s Ubuntu repo (packages.microsoft.com) returns 403, causing the job to exit before tests run.
I didn’t change CI or system dependencies, but I’m happy to rerun or adjust if needed.

Yes, I assume you can ignore those failures, that looks like some temporary network issue

[vkverma9534]

@jorisvandenbossche I think I should raise a new PR by creating a new branch since my attempts to make the checks pass have worsened them. is that ok?

[jorisvandenbossche]

No need to do so! If you can fix the indentation in pandas/core/arrays/_arrow_string_mixins.py, then that should be fine. You can do that by pushing more commits to this branch

[vkverma9534]

Okay I would try and fix them.