fix: call cascade listeners for unassigned values

[zepfred]

No description provided.

[triceo]

Will need refactoring.

[triceo]

I'll run some benchmarks overnight.
This is likely to affect performance, I want to know by how much.

[triceo]

There is a performance regression, which is unavoidable. The code now does more than it did before. Performance regressions are acceptable, if they fix incorrect behavior.

However, I made a whole bunch of changes to minimize the regression. There is a simple underlying principle to all of my changes: don't do things that don't need doing. Please review the changes and ask questions in case anything is unclear.

[triceo]

I'll have the final benchmark results in a few hours.

[triceo]

I wasn't able to measure any regression anymore that I could attribute to this PR. LGTM after the Sonar issues are fixed.

[Copilot]

Pull Request Overview

This PR fixes the cascade listener handling for unassigned values and adds several tests and improvements to support this behavior. Key changes include:

• Added tests for LinkedIdentityHashSet, ElementAwareList, and cascading update behavior.
• Updated TestdataSingleCascadingValue and MoveDirectorTest to verify that cascade updates are correctly invoked and undone.
• Enhanced VariableListenerSupport and related notification classes to support cascade updates for unassigned values.

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
core/src/test/java/ai/timefold/solver/core/impl/util/LinkedIdentityHashSetTest.java	New tests for the identity-based set implementation.
core/src/test/java/ai/timefold/solver/core/impl/util/ElementAwareListTest.java	Added clear() test to ensure proper list resetting.
core/src/test/java/ai/timefold/solver/core/impl/testdata/domain/cascade/single_var/TestdataSingleCascadingValue.java	Introduced null-check to reset cascade values when the entity is unassigned.
core/src/test/java/ai/timefold/solver/core/impl/testdata/domain/cascade/single_var/TestdataSingleCascadingEasyScoreCalculator.java	New score calculator for cascading update testing.
core/src/test/java/ai/timefold/solver/core/impl/move/director/MoveDirectorTest.java	Added a test to verify undo behavior of cascading updates.
core/src/main/java/ai/timefold/solver/core/impl/util/LinkedIdentityHashSet.java	New implementation of a set using identity comparisons.
core/src/main/java/ai/timefold/solver/core/impl/util/ElementAwareList.java	Updated iterator to return an empty iterator when appropriate and added clear() support.
core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/VariableListenerSupport.java	Enhanced to add cascade notifications for unassigned values and refactored related logic.
core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/Notification.java	Updated the list variable change notification creation to return a ListVariableChangedNotification.
core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/ListVariableEvent.java	Removed redundant record as part of the refactoring.
core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/ListVariableChangedNotification.java	Made public to ensure accessibility in cascade update contexts.
core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/AbstractNotification.java	Added getEntity() accessor to support notification logic.

Comments suppressed due to low confidence (2)

core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/VariableListenerSupport.java:245

• [nitpick] Consider renaming 'unassignedValueWithEmptyInverseEntitySet' to a more concise name (e.g., 'unassignedEmptyInverseSet') to improve readability in the cascade update logic.

unassignedValueWithEmptyInverseEntitySet.add(element);

core/src/main/java/ai/timefold/solver/core/impl/domain/variable/listener/support/VariableListenerSupport.java:320

• [nitpick] Consider adding an inline comment explaining why the value is removed from the unassigned set here, to clarify its role in the cascade update process.

unassignedValueWithEmptyInverseEntitySet.remove(value);

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
98.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud