[chrikrah]

Rationale for this change

tdigest and hash_tdigest accept a q outside [0, 1] and return NaN, while quantile raises ArrowInvalid on the same value. TDigestOptions and QuantileOptions document the range as a requirement ("All values must be in [0, 1]", python/pyarrow/_compute.pyx; api_aggregate.h says the same). q=NaN also gets past the check in quantile, and it aborts all three on a Debug build. Closes #55372.

What changes are included in this PR?

CheckQuantileOptions's range loop moves to ValidateQuantileLevels in aggregate_internal.h, negated so that NaN fails it. TDigestInit and GroupedTDigestImpl::Init now call it, with the message quantile already uses.

Are these changes tested?

Yes. TestTDigestKernel.InvalidQuantileLevel, TestQuantileKernel.InvalidQuantileLevel and GroupBy.TDigestInvalidQuantileLevel are new, each with NaN and empty input. test_quantile and test_tdigest gain cases.

# base 6bddeb67e, Debug, g++ 13.3.0, Linux x86_64 (cmake line on request)
$ debug/arrow-compute-aggregate-test
[  PASSED  ] 347 tests.              # base: 345
$ debug/arrow-acero-hash-aggregate-test
[  PASSED  ] 98 tests.               # base: 97
# old condition restored (level < 0 || level > 1), each new test run alone with --gtest_filter: all three abort, exit 134
$ python -m pytest -q ttd.py         # test_quantile, test_tdigest copied out, pyarrow 26.0.0 wheel: both DID NOT RAISE ValueError
# not run: the Python tests against a pyarrow built from this branch, and the wider C++ suites

Are there any user-facing changes?

Yes. A q outside [0, 1], NaN included, now raises ArrowInvalid from tdigest and hash_tdigest. It used to return NaN, or null on empty or all-null input.

quantile now raises on q=NaN too. On the 26.0.0 wheel it returned NaN, or with interpolation='lower' or 'nearest' a real-looking 1.0 on [1.0, 2.0, 3.0].

The check runs at init here and at exec in quantile, so a bad option fails before any data is read. Tell me if you'd rather have it at exec in both.

• GitHub Issue: [C++][Python] tdigest and hash_tdigest return NaN for q outside [0, 1]; quantile raises #55372

[github-actions]

⚠️ GitHub issue #55372 has been automatically assigned in GitHub to PR creator.

[Reranko05]

This is a new PR. You should be able to see checkboxes in the PR description template regarding AI-generated code https://arrow.apache.org/docs/dev/developers/overview.html#ai-generated-code. Why were they removed?