chore: prevent NPE in solution annotation processing

[triceo]

Was bringing our Sonar rating down to C.

[Copilot]

Pull Request Overview

Refactors solution annotation processing to centralize null-checks and improve error reporting, helping to prevent NullPointerExceptions.

• Extracted inline annotation lookup logic into a dedicated extractPlanningSolutionAnnotation method.
• Added @NonNull annotation and detailed error messages for missing @PlanningSolution.
• Simplified cloner retrieval by calling annotation.solutionCloner() directly.

Comments suppressed due to low confidence (3)

core/src/main/java/ai/timefold/solver/core/impl/domain/solution/descriptor/SolutionDescriptor.java:411

• [nitpick] Consider adding a JavaDoc comment to extractPlanningSolutionAnnotation to explain its purpose, return guarantee, and the conditions under which it throws an exception.

    private @NonNull PlanningSolution extractPlanningSolutionAnnotation() {

core/src/main/java/ai/timefold/solver/core/impl/domain/solution/descriptor/SolutionDescriptor.java:411

• There are no tests covering the new extractPlanningSolutionAnnotation method, especially for cases where the annotation is on the superclass or missing entirely. Consider adding unit tests for these scenarios to ensure correct behavior.

    private @NonNull PlanningSolution extractPlanningSolutionAnnotation() {

core/src/main/java/ai/timefold/solver/core/impl/domain/solution/descriptor/SolutionDescriptor.java:402

• The original logic used PlanningSolution.NullSolutionCloner when only a superclass annotation was present. This change now applies the superclass's solutionCloner, which alters behavior. Confirm whether this is intentional or adjust to preserve the previous fallback behavior.

        var solutionClonerClass = annotation.solutionCloner();

[sonarqubecloud]

Quality Gate failed

Failed conditions
69.6% Coverage on New Code (required ≥ 70%)

See analysis details on SonarQube Cloud