Fix FORM's RNTuple backend build against ROOT 6.40

[olantwin]

ROOT 6.40 moved RRawPtrWriteEntry from ROOT::Experimental::Detail to ROOT::Detail. Select the namespace with a ROOT version check so the RNTuple storage backend (FORM_USE_RNTUPLE_STORAGE=ON) compiles against both ROOT 6.38 and 6.40.

Fixes #712.

• Code
  • Added ROOT version-aware handling for RRawPtrWriteEntry.
  • Uses ROOT::Detail with ROOT 6.40+ and ROOT::Experimental::Detail for ROOT 6.38.
  • Updated the m_entry member to use the compatibility alias.
• Compatibility
  • Enables the RNTuple storage backend to compile with ROOT 6.38 and newer, including ROOT 6.40.

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• form/root_storage/root_rntuple_write_container.hpp

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• form/root_storage/root_rntuple_write_container.hpp

**/*.{hpp,cpp}

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Enforce 100-character line limit and 2-space indentation in C++ code via .clang-format
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Files:

• form/root_storage/root_rntuple_write_container.hpp

**/*.hpp

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• form/root_storage/root_rntuple_write_container.hpp

🔇 Additional comments (2)

form/root_storage/root_rntuple_write_container.hpp (2)

8-9: LGTM!

Also applies to: 19-30

---

19-39: 🎯 Functional Correctness

Compile both ROOT namespace branches in CI.

A single ROOT build cannot exercise the other preprocessor branch. ROOT 6.38 uses ROOT::Experimental::Detail::RRawPtrWriteEntry, while ROOT 6.40’s writer API uses ROOT::Detail::RRawPtrWriteEntry; confirm FORM_USE_RNTUPLE_STORAGE=ON builds against both versions. (root.cern)

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📝 Walkthrough

Walkthrough

The RNTuple write container now supports ROOT versions before and from 6.40 by conditionally selecting the namespace of RRawPtrWriteEntry.

Changes

ROOT RNTuple compatibility

Layer / File(s)	Summary
Version-aware RRawPtrWriteEntry type form/root_storage/root_rntuple_write_container.hpp	Includes RVersion.h, selects the ROOT namespace based on ROOT_VERSION_CODE, and uses the resulting alias for m_entry.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• Framework-R-D/phlex#635: Introduced the RNTuple write container member declaration that this change makes ROOT-version-aware.

Suggested reviewers: wwuoneway

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly states the main change: fixing the RNTuple backend build for ROOT 6.40.
Linked Issues check	✅ Passed	The change matches #712 by handling the RRawPtrWriteEntry namespace move while preserving ROOT 6.38 compatibility.
Out of Scope Changes check	✅ Passed	The diff appears narrowly scoped to the ROOT version-conditional type fix needed for the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main     #749      +/-   ##
==========================================
- Coverage   83.85%   83.84%   -0.02%     
==========================================
  Files         172      172              
  Lines        7198     7198              
  Branches      845      845              
==========================================
- Hits         6036     6035       -1     
- Misses        882      883       +1     
  Partials      280      280              

Flag	Coverage Δ
scripts	80.13% <ø> (ø)
unittests	85.71% <ø> (-0.03%)	⬇️

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[gemmeren]

Thanks Oliver, LGTM, but @aolivier23 should have a look.

[aolivier23]

Looks good to me. Thank you for pushing this upstream @olantwin @gemmeren

[olantwin]

Thanks for the reviews and for accepting the fix!