Add C++ API reference to Sphinx docs

[bdice]

Summary

Integrate cuML’s Doxygen-generated C++ API into the Sphinx documentation using Breathe. This adds namespace references for ML, MLCommon, and cuml::genetic to the main documentation navigation and normalizes Doxygen 1.9.1 XML constructs that Sphinx cannot represent.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 3dc31f76-22da-46a9-ae94-39eef3e5d1ab

📥 Commits

Reviewing files that changed from the base of the PR and between 2120ad5 and d016b04.

📒 Files selected for processing (6)

• conda/environments/all_cuda-129_arch-aarch64.yaml
• conda/environments/all_cuda-129_arch-x86_64.yaml
• conda/environments/all_cuda-133_arch-aarch64.yaml
• conda/environments/all_cuda-133_arch-x86_64.yaml
• dependencies.yaml
• docs/source/cpp/index.rst

🚧 Files skipped from review as they are similar to previous changes (3)

• conda/environments/all_cuda-129_arch-aarch64.yaml
• conda/environments/all_cuda-133_arch-aarch64.yaml
• docs/source/cpp/index.rst

Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review.

---

📝 Summary

Summary by CodeRabbit

• Documentation

  • Added a C++ API documentation section covering the ML, MLCommon, and genetic namespaces.
  • Integrated generated C++ API references into the documentation navigation.
  • Enabled richer API reference generation and Sphinx integration.

• Chores

  • Added required documentation tooling to supported CUDA environments.
  • Excluded generated Doxygen XML artifacts from version control.

Walkthrough

Changes

C++ API documentation

Layer / File(s)	Summary
Doxygen XML generation and dependencies .gitignore, cpp/Doxyfile.in, dependencies.yaml, conda/environments/*	Doxygen XML generation is enabled. breathe is added to documentation dependencies. The generated XML directory is ignored.
Doxygen XML cleanup and Breathe configuration docs/source/conf.py	Sphinx registers Breathe and maps the cuML XML output. clean_doxygen_xml removes unsupported or conflicting XML elements and repairs enum-value IDs before documentation processing.
C++ API documentation pages docs/source/cpp/*, docs/source/index.rst	The documentation tree adds C++ API pages for the ML, MLCommon, and cuml::genetic namespaces.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to d016b

This change publishes generated C++ API namespace documentation through the Sphinx site. No concrete merge-blocking risk remains in the supplied change context.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (6 skipped: 6 …	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 clearly explains the integration of Doxygen-generated C++ API documentation into Sphinx with Breathe and identifies the documented namespaces.
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding the C++ API reference to the Sphinx documentation.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (6 skipped: 6 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands.}

[jcrist]

We don't currently consider the C++ api public in any way - I'd worry about the effect of publishing the docs for something that we make no promise is usable outside of the python library (and no promises of deprecations/no breaking changes). Personally I wouldn't want these docs to be published at this point.

cc @csadorf for another opinion.

[csadorf]

We don't currently consider the C++ api public in any way - I'd worry about the effect of publishing the docs for something that we make no promise is usable outside of the python library (and no promises of deprecations/no breaking changes). Personally I wouldn't want these docs to be published at this point.

cc @csadorf for another opinion.

I'm also against promoting the C++ API within our documentation in this way at this point in time. I wouldn't describe it as "not public at all", but it's certainly not as stable as the Python API, we don't have a formalized deprecation policy at the moment, and we are making breaking changes whenever needed. It is my intention that we work towards improving and stabilizing the C++ API and eventually promote it as more stable, but at this point, I agree with @jcrist , I'm afraid it would set the wrong expectations.

[bdice]

We currently publish C++ docs for libcuml. It is linked from https://docs.rapids.ai/api/#rapids-libraries and points to https://docs.rapids.ai/api/libcuml/nightly/.

We are dropping publication of all our Doxygen sites to reduce maintenance cost. If you don't want Sphinx docs, that's fine, but we won't have Doxygen either.