GH-51659: [R] Expose ignore_extra_columns and pad_short_rows CSV pars…

[rajaryan2007]

Rationale for this change

Arrow C++ 26.0.0 added two new arrow::csv::ParseOptions fields:

• ignore_extra_columns (GH-50967: [C++] Allow CSV reader to ignore extra columns in rows with more columns #51118): rows with more columns than expected have
  the extra columns dropped instead of erroring
• pad_short_rows (GH-50925: [C++] Allow CSV reader to pad rows with missing trailing fields #50926): rows with fewer columns than expected are padded
  with nulls instead of erroring

Neither could be set from R, so read_csv_arrow() and open_csv_dataset()
error on ragged CSV with no way to opt into the C++ behaviour.

# before: Error: CSV parse error: Expected 3 columns, got 2
read_csv_arrow(I("a,b,c\n1,2,9\n3"))

# after
read_csv_arrow(I("a,b,c\n1,2,9\n3"),
               parse_options = csv_parse_options(pad_short_rows = TRUE))
#>   a  b  c
#> 1 1  2  9
#> 2 3 NA NA

Are these changes tested?

Yes. test-csv.R gains pad_short_rows and ignore_extra_columns parse options, covering each option alone, both together, the plain-list form, and the CsvParseOptions$create() entry point. It also asserts ragged input still errors by default, pinning the new defaults.

Verified locally with R 4.4.3: the full testthat suite passes (6,561 assertions, 0 failures, 0 errors), and the new test was confirmed to fail against the pre-change r/src/csv.cpp.

Are there any user-facing changes?

Additive: csv_parse_options() and CsvParseOptions$create() accept two new arguments, both defaulting to FALSE to match the C++ defaults, so existing code is unaffected.

Was AI used for this PR?

i used ai for build and some someother help .

PR code and description written by:

• Human
• AI

Reviewed before submission by:

• Human
• AI
• Not reviewed

• GitHub Issue: [R] Expose ignore_extra_columns and pad_short_rows CSV parse options #51659

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #51659 has been automatically assigned in GitHub to PR creator.

[thisisnic]

Thanks for taking the time to make this PR! This is almost there, just a few changes to suggest. I've put some of them inline.

One more thing is that the CsvReadOptions docs block above has its own list of the arguments CsvParseOptions$create() takes, so please could you add pad_short_rows and ignore_extra_columns there too?

Let me know if you have any questions!

[rajaryan2007]

done : )