fix(csv): correct to_csv quoting documentation and expose QUOTE_NONE

[a-hirota]

Description

The existing documentation incorrectly stated that to_csv follows "Pandas csv.QUOTE_NONNUMERIC", but the actual default behavior is csv.QUOTE_MINIMAL. This PR corrects the documentation.

Additionally, libcudf already supports quote_style::NONE in the CSV writer (cpp/src/io/csv/writer_impl.cu), but this was not exposed in the Python API. This PR adds the quoting parameter to DataFrame.to_csv() to allow users to use csv.QUOTE_NONE, matching pandas API.

Changes

• Fix incorrect docstring (QUOTE_NONNUMERIC → QUOTE_MINIMAL)
• Add quoting parameter to to_csv() exposing libcudf's existing functionality
• Add quoting method to CsvWriterOptionsBuilder in pylibcudf
• Add tests for quoting functionality (pandas compatibility verified)

Supported quoting styles

Style	Description
csv.QUOTE_MINIMAL (default)	Quote only fields with special characters
csv.QUOTE_NONE	Never quote fields

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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[Copilot]

Pull request overview

This pull request fixes incorrect CSV documentation and exposes the quoting parameter to allow users to control field quoting behavior in CSV output. The changes enable pandas-compatible CSV quoting with support for csv.QUOTE_MINIMAL (default) and csv.QUOTE_NONE.

Changes:

• Corrected documentation stating the default quoting behavior is csv.QUOTE_MINIMAL (not csv.QUOTE_NONNUMERIC)
• Added quoting parameter to DataFrame.to_csv() and cudf.io.csv.to_csv()
• Exposed libcudf's existing quote_style::NONE support through pylibcudf's CsvWriterOptionsBuilder

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
python/pylibcudf/pylibcudf/libcudf/io/csv.pxd	Added C++ binding declaration for quoting() method in csv_writer_options_builder
python/pylibcudf/pylibcudf/io/csv.pyx	Implemented quoting() method in CsvWriterOptionsBuilder with documentation
python/pylibcudf/pylibcudf/io/csv.pyi	Added type stub for quoting() method with QuoteStyle parameter
python/pylibcudf/pylibcudf/io/csv.pxd	Added Cython declaration for quoting() method
python/cudf/cudf/utils/ioutils.py	Updated docstring to document the quoting parameter and correct default behavior
python/cudf/cudf/tests/input_output/test_csv.py	Added comprehensive tests for quoting functionality including pandas compatibility, special characters, unsupported styles, and edge cases
python/cudf/cudf/io/csv.py	Added quoting parameter with validation and mapping to QuoteStyle enum
python/cudf/cudf/core/dataframe.py	Added quoting parameter to DataFrame.to_csv() with default handling

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[mroeschke]

Thanks a few comments

[mroeschke]

/ok to test 79c68a0

[Matt711]

/ok to test dc27c6a

[vyasr]

/ok to test eda5888

[coderabbitai]

📝 Walkthrough

Walkthrough

CSV writing now accepts a quoting option from DataFrame.to_csv through cudf.io.csv into libcudf writer configuration. Tests and docs were updated to cover supported quoting modes and unsupported values.

Changes

CSV quoting support

Layer / File(s)	Summary
Public entrypoint and docs python/cudf/cudf/core/dataframe.py, python/cudf/cudf/utils/ioutils.py	DataFrame.to_csv adds quoting and forwards it to CSV writing; the CSV docstring text describes supported quoting constants and unsupported modes.
CSV writer behavior python/cudf/cudf/io/csv.py, python/cudf/cudf/tests/input_output/test_csv.py	cudf.io.csv.to_csv defaults, validates, and propagates quoting into writer configuration, and tests cover supported values, unsupported values, special characters, and empty frames.
Pylibcudf builder surface python/pylibcudf/pylibcudf/io/csv.pxd, python/pylibcudf/pylibcudf/io/csv.pyi, python/pylibcudf/pylibcudf/io/csv.pyx, python/pylibcudf/pylibcudf/libcudf/io/csv.pxd	The CSV writer options builder gains a quoting fluent method across the Python bindings and libcudf interface declarations.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested labels

bug, 5 - Ready to Merge

Suggested reviewers

• mroeschke

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description is directly related to the changeset and matches the implemented quoting API and documentation updates.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title accurately summarizes the main changes: documenting quoting behavior and exposing QUOTE_NONE support in to_csv.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@python/cudf/cudf/tests/input_output/test_csv.py`:
- Around line 2310-2312: The pytest.raises match pattern in the CSV test uses a
regex with metacharacters but is written as a normal string, which triggers Ruff
RUF043. Update the relevant pytest.raises call in test_csv.py to use a raw
string for the match argument, keeping the existing NotImplementedError
assertion and the same regex text. Use the pytest.raises block around the
quoting-related test as the locator.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Run ID: c70d63e8-f7fa-4f13-a845-6005a5e0af4f

📥 Commits

Reviewing files that changed from the base of the PR and between e5e329b and eda5888.

📒 Files selected for processing (8)

• python/cudf/cudf/core/dataframe.py
• python/cudf/cudf/io/csv.py
• python/cudf/cudf/tests/input_output/test_csv.py
• python/cudf/cudf/utils/ioutils.py
• python/pylibcudf/pylibcudf/io/csv.pxd
• python/pylibcudf/pylibcudf/io/csv.pyi
• python/pylibcudf/pylibcudf/io/csv.pyx
• python/pylibcudf/pylibcudf/libcudf/io/csv.pxd

[vyasr]

/ok to test fccf1f8