fix: Graph now notify updater when cycles are formed or broken

[Christopher-Chianelli]

Previously, the updater only considered nodes that were changed from an edge insertion or deletion. However, an edge insertion/deletion can also change the looped status of a disconnected node. For example, if we have a -> b and b -> a, and we
remove a -> b, only b is marked as changed. This is incorrect, since a changed indirectly, since it is no longer looped. Thus, the graph implementations now mark any nodes whose SCC change from singleton to multinode (looped) and vice-versa.

[Copilot]

Pull Request Overview

This PR enhances the graph implementation to notify the updater when nodes’ looped (cycle) status changes by propagating a shared BitSet through graph operations and recording SCC status flips.

• Method signatures for commitChanges, addEdge, and removeEdge now accept a BitSet changed to mark nodes whose cycle membership toggles.
• Tests in VariableListenerSupportTest are updated to pass the new changed parameter; a new DefaultTopologicalGraphTest is added.
• DefaultTopologicalOrderGraph tracks and flags nodes whose SCC size moves between singleton and multi-node loops, and adds a toString for debugging.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
VariableListenerSupportTest.java	Updated overridden addEdge/removeEdge to include BitSet changed.
DefaultTopologicalGraphTest.java	New test class for DefaultTopologicalOrderGraph.
TopologicalOrderGraph.java	Changed signatures of commitChanges, addEdge, removeEdge to take BitSet changed.
DefaultVariableReferenceGraph.java	Pass the shared changed BitSet into graph operations and commit.
DefaultTopologicalOrderGraph.java	Added isNodeInLoopedComponent, track SCC status flips, and debug toString().

Comments suppressed due to low confidence (2)

core/src/main/java/ai/timefold/solver/core/impl/domain/variable/declarative/TopologicalOrderGraph.java:13

• The new changed parameter isn’t documented in the Javadoc. Please add an @param changed explaining that it is a BitSet used to collect nodes whose looped status has changed.

void commitChanges(BitSet changed);

core/src/test/java/ai/timefold/solver/core/impl/domain/variable/declarative/DefaultTopologicalGraphTest.java:5

• [nitpick] The test class name omits "Order" and doesn’t match the tested DefaultTopologicalOrderGraph. Consider renaming this to DefaultTopologicalOrderGraphTest for consistency.

public class DefaultTopologicalGraphTest extends AbstractTopologicalGraphTest<DefaultTopologicalOrderGraph> {

[sonarqubecloud]

Quality Gate failed

Failed conditions
53.8% Coverage on New Code (required ≥ 70%)

See analysis details on SonarQube Cloud