GH-33708: [R] read_csv_arrow()'s timestamp_parsers parameter is a bit light on documentation and doesn't appear to do anything

[thisisnic]

Rationale for this change

timestamp_parsers works, but the docs didn't say that supplying parsers replaces the default ISO-8601 parser, or that a non-matching parser silently falls through to a string column during type inference. Passing convert_options alongside timestamp_parsers also silently discarded the latter.

What changes are included in this PR?

Rewrites the timestamp_parsers documentation and adds an example showing how to keep ISO-8601 as a fallback. Adds a warning when timestamp_parsers is ignored because convert_options was supplied, in both the reader and dataset paths. Unskips the dataset test for this option.

Are these changes tested?

Yes, new tests for the inference path, the ISO-8601 fallback, and the warning.

Are there any user-facing changes?

Yes, a new warning when timestamp_parsers is passed together with convert_options.

• GitHub Issue: [R] read_csv_arrow()'s timestamp_parsers parameter is a bit light on documentation and doesn't appear to do anything #33708

[github-actions]

⚠️ GitHub issue #33708 has been automatically assigned in GitHub to PR creator.

[Copilot]

🟢 Approval recommended

The changes align with the stated issue/PR rationale, add appropriate warnings for a previously silent override, and include test coverage for the updated behavior.

Pull request overview

Improves the R CSV reader/dataset UX around timestamp_parsers by clarifying its semantics, surfacing a previously silent override case, and adding tests to lock in the intended behavior.

Changes:

• Expanded timestamp_parsers documentation (replacement of ISO-8601 default, inference fallthrough-to-string behavior, and ISO-8601 fallback example).
• Added warnings when timestamp_parsers is supplied alongside convert_options (reader + dataset paths).
• Added/updated tests (including unskipping the dataset case) to cover inference, ISO-8601 fallback, and the new warning.

File summaries

File	Description
r/R/csv.R	Updates roxygen docs for timestamp_parsers/convert_options, adds example, and warns when convert_options overrides timestamp_parsers in the reader path.
r/R/dataset-format.R	Warns when timestamp_parsers is provided but ignored due to explicit convert_options in the dataset/file-format path.
r/tests/testthat/test-csv.R	Adds tests covering inference behavior, ISO-8601 fallback behavior, and the new warning for read_csv_arrow().
r/tests/testthat/test-dataset-csv.R	Unskips and updates dataset test coverage for timestamp_parsers, plus warning coverage when convert_options is supplied.
r/man/read_delim_arrow.Rd	Regenerates man page text to reflect updated docs and example.
r/man/open_delim_dataset.Rd	Regenerates man page text to reflect updated docs.
r/man/CsvReadOptions.Rd	Updates timestamp_parsers documentation to reflect replacement semantics and fallback note.
r/man/csv_convert_options.Rd	Regenerates man page text to reflect updated timestamp_parsers documentation.

Review details

Files not reviewed (4)

• r/man/CsvReadOptions.Rd: Generated file
• r/man/csv_convert_options.Rd: Generated file
• r/man/open_delim_dataset.Rd: Generated file
• r/man/read_delim_arrow.Rd: Generated file

• Files reviewed: 4/8 changed files
• Comments generated: 0
• Review effort level: Lite

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