GH-38712: [Python] Remove dead code in _reconstruct_block

[AlenkaF]

Rationale for this change

It seems the object case in _reconstruct_block is a dead code and is not needed anymore so therefore could be removed.

What changes are included in this PR?

Removal of the object case in _reconstruct_block code. Was also looking at the arrow_to_pandas.cc code to see if there is any dead code present and I couldn't find any.

Are these changes tested?

The change in this PR should not make any of the existing tests fail.

Are there any user-facing changes?

There shouldn't be.

• Closes: [Python] Remove dead code in _reconstruct_block (pandas_compat.py) #38712

[jorisvandenbossche]

I don't expect there to be any code in pandas_to_arrow.cc for this, I think the serialization used a different code path (and only shared this reconstruct_blocks)

[pitrou]

@AlenkaF Can you fix the lint issue (see CI)?

[jorisvandenbossche]

I think the linting is something R related:

> lintr::lint_package('/arrow/r')
Warning message:
> 
> 
In validate_config_file(config, config_file, default_settings) :
  Found unused settings in config '/arrow/r/.lintr': license
INFO:archery:Running Docker linter
1
Error: `docker-compose --file /home/runner/work/arrow/arrow/docker-compose.yml run --rm -e GITHUB_ACTIONS=true ubuntu-lint` exited with a non-zero exit code 1, see the process log above.

(I think I have seen it happening last week as well, although it doesn't show up on the main branch)

[pitrou]

There is a Python lint failure as well, though.

[pitrou]

cc @paleolimbot for the R lint issue.

[jorisvandenbossche]

R lint issue might be related to #38639, although that is already merged in the branch that is being used for this PR ..

[jorisvandenbossche]

There is a Python lint failure as well, though.

Ah, indeed .. The output formatting is not great, easy to look over ;)

[AlenkaF]

Oh, I totally missed that as I also thought is was only R connected failure! =) Will correct 👍

[paleolimbot]

It looks like you found it, but I was going to say that the "warning" appears on master as well so I don't think it's causing the job to fail: https://github.com/apache/arrow/actions/runs/6866609338/job/18673200564#step:5:981

[jorisvandenbossche]

Indeed, it was only printing the warning. But because the linter was failing because of a python lint issue further up, it was easy to think the R issue was causing the failure .. Would it be easy to avoid the warning?

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 5 benchmarking runs that have been run so far on merge-commit 5b17b84.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 3 possible false positives for unstable benchmarks that are known to sometimes produce them.