Add SillyEqualsCheck recipe (RSPEC-S2159)

[timtebeek]

Summary

Implements SonarQube rule S2159 "Silly equality checks should not be made", which detects .equals() calls that always return false.

The recipe transforms equals(null) checks to == null comparisons and replaces array.equals() with Arrays.equals(). It also flags comparisons between unrelated types and array-vs-non-array comparisons as search results.

Changes

• New recipe: SillyEqualsCheck with comprehensive unit tests
• Handles negation patterns (!x.equals(null) → x != null)
• Auto-fixes: null checks and array equality comparisons
• Search results: unrelated types and mixed array/non-array comparisons

[timtebeek]

Validation: Tested at scale against Apache Maven (80 repos)

Ran SillyEqualsCheck against 80 Apache Maven repositories using pre-built LSTs from Moderne.

Results

• 1 repository matched: apache/maven-2
• 36 files changed — all in maven-model/src/test/java/org/apache/maven/model/
• 79 repositories: no changes (clean pass, no errors)

All changes are .equals(null) → == null

Every match follows the same pattern in testEqualsNullSafe() methods:

-        assertFalse( new ActivationFile().equals( null ) );
+        assertFalse( new ActivationFile() == null );

Affected test classes: ActivationFileTest, ActivationOSTest, ActivationPropertyTest, ActivationTest, BuildTest, CiManagementTest, ContributorTest, DependencyManagementTest, DependencyTest, DeploymentRepositoryTest, DeveloperTest, DistributionManagementTest, ExclusionTest, ExtensionTest, IssueManagementTest, LicenseTest, MailingListTest, ModelTest, NotifierTest, OrganizationTest, ParentTest, PluginConfigurationTest, PluginContainerTest, PluginExecutionTest, PluginManagementTest, PluginTest, PrerequisitesTest, ProfileTest, RelocationTest, ReportPluginTest, ReportSetTest, ReportingTest, RepositoryPolicyTest, RepositoryTest, ResourceTest, ScmTest, SiteTest

Assessment

• No false positives
• No crashes or errors
• No array or unrelated-type matches in this corpus (expected for Maven model test code)
• Formatting and whitespace preserved correctly

[steve-aom-elliott]

Makes sense to me. Might want to update the copyright years to 2026, but that's about it.