fix(mcconfigurator): Fix to run without TGeant3

[karabowi]

The MCConfigurator required TGeant3 and TGeant4 to run. Added compiler flags to enable running without any given transport engine.

Fixes issue #1620.

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Checklist:

• Followed the Contributing Guidelines

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR refactors mcconfigurator's build dependencies and optional feature support. It decouples mcconfigurator from hard-coded Geant3/Geant4/FastSim requirements by making these dependencies optional and detectable at compile-time via preprocessor macros. mcconfigurator now builds with only yaml-cpp present, while Geant3/Geant4/FastSim support is conditionally compiled when available.

Changes

Cohort / File(s)	Summary
Build configuration—dependency loosening fairroot/CMakeLists.txt	Changed mcconfigurator add_subdirectory condition from (Geant3_FOUND AND Geant4VMC_FOUND AND yaml-cpp_FOUND AND TARGET FairRoot::FastSim) to (yaml-cpp_FOUND), decoupling from Geant/FastSim hard requirements.
Build configuration—feature flags and linkage fairroot/mcconfigurator/CMakeLists.txt	Added public compile definitions (FAIRROOT_HAS_GEANT3, FAIRROOT_HAS_GEANT4, FAIRROOT_HAS_FASTSIM) when respective components are found; converted private linkage of geant321, geant4vmc, and FairRoot::FastSim to conditional public linkage; added EXTRA_INCLUDE_DIRS to ROOT dictionary target; updated copyright year.
CMake reorganization examples/CMakeLists.txt	Updated copyright year (2014-2022 → 2014-2025); moved add_subdirectory(common/gconfig) from inside Geant3_FOUND conditional to unconditional pre-check (gated on MCConfigurator).
Conditional compilation implementation fairroot/mcconfigurator/FairYamlVMCConfig.cxx	Replaced unconditional includes of FairFastSimRunConfiguration.h, TGeant3.h, TGeant3TGeo.h, and TGeant4.h with #ifdef-guarded includes (FAIRROOT_HAS_*); wrapped SetupPostInit(), SetupGeant3(), and SetupGeant4() implementations with feature guards; added fatal error messages when required features are unavailable; refactored Geant4 setup to conditionally build FastSim TG4RunConfiguration.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20–25 minutes

• fairroot/CMakeLists.txt: Verify that loosening the mcconfigurator condition from four requirements to one does not break supported build scenarios; ensure this aligns with downstream consumers.
• fairroot/mcconfigurator/CMakeLists.txt: Confirm all three conditional PUBLIC link targets and their guards are correctly paired with the new compile definitions.
• FairYamlVMCConfig.cxx: Cross-check that all #ifdef preprocessor guards in the source file match the corresponding compile definition conditions in CMakeLists.txt; verify fatal error messages are user-friendly and direct users to rebuild with required support.
• Integration: Ensure the interplay between loosened build conditions and conditional compilation guards allows graceful degradation when optional components are absent.

Possibly related PRs

• fix(build): Make trackbase build possible without Geant3 #1611: Directly related—both PRs modify fairroot/CMakeLists.txt to decouple component inclusion from hard Geant3 requirements by moving or conditional-checking the mcconfigurator addition.

Suggested reviewers

• ChristianTackeGSI

Pre-merge checks and finishing touches

❌ 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%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding support for running MCConfigurator without TGeant3, which is the core focus of the changeset.
Description check	✅ Passed	The description is directly related to the changeset, explaining that compiler flags were added to enable running without transport engines and referencing the corresponding issue.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 2

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

fairroot/mcconfigurator/FairYamlVMCConfig.cxx (1)

68-131: Potential unused parameter warning when Geant4 is disabled.

When FAIRROOT_HAS_GEANT4 is not defined, the mcEngine parameter is unused, which may trigger compiler warnings.

Apply this diff to suppress the warning:

 void FairYamlVMCConfig::SetupPostInit(const char* mcEngine)
 {
 #ifdef FAIRROOT_HAS_GEANT4
     if (!fPostInitFlag) {
 ...
 #else
+    (void)mcEngine;  // Suppress unused parameter warning
     LOG(fatal) << "FairYamlVMCConfig::SetupPostInit() - Geant4 support is not available! "
                << "FairRoot was compiled without Geant4. "
                << "Please use TGeant3 or recompile FairRoot with Geant4 support.";
 
 #endif
 }

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e22c961 and e7f4d88.

📒 Files selected for processing (4)

• examples/CMakeLists.txt (2 hunks)
• fairroot/CMakeLists.txt (1 hunks)
• fairroot/mcconfigurator/CMakeLists.txt (2 hunks)
• fairroot/mcconfigurator/FairYamlVMCConfig.cxx (8 hunks)

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2024-06-14T10:16:00.050Z

Learnt from: dennisklein
Repo: FairRootGroup/FairRoot PR: 1560
File: cmake/private/FairRootConfig.cmake.in:13-13
Timestamp: 2024-06-14T10:16:00.050Z
Learning: `PACKAGE_PROJECT_CMAKEMOD_DIR` is defined by the call to `configure_package_config_file()` in the CMake configuration process for FairRoot.

Applied to files:

• fairroot/CMakeLists.txt
• examples/CMakeLists.txt
• fairroot/mcconfigurator/FairYamlVMCConfig.cxx
• fairroot/mcconfigurator/CMakeLists.txt

🔇 Additional comments (7)

fairroot/mcconfigurator/FairYamlVMCConfig.cxx (3)

31-41: LGTM! Conditional includes are correctly structured.

The guarded includes properly isolate optional dependencies, preventing compilation errors when Geant3/Geant4/FastSim are not available.

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133-181: LGTM!

The conditional compilation guard and fatal error message are correctly implemented, providing clear guidance when Geant3 support is unavailable.

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244-249: LGTM!

The fallback fatal error message is consistent with the Geant3 pattern and provides clear guidance.

examples/CMakeLists.txt (1)

14-16: LGTM!

Moving the gconfig subdirectory inclusion outside the Geant3_FOUND block correctly reflects that MCConfigurator now only requires yaml-cpp to build.

fairroot/CMakeLists.txt (1)

43-45: LGTM!

Relaxing the condition to only require yaml-cpp_FOUND correctly enables building MCConfigurator without transport engines. The individual backend dependencies are now properly handled via compile definitions in mcconfigurator/CMakeLists.txt.

fairroot/mcconfigurator/CMakeLists.txt (2)

25-34: LGTM!

The compile definitions are correctly set based on the availability of each component, and PUBLIC visibility ensures consumers can also use these guards when including MCConfigurator headers.

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56-61: LGTM!

The conditional linking of FairRoot::FastSim correctly requires both Geant4VMC_FOUND and the target existence.