SONARJAVA-5730 S1301 Should not raise on switch over small enums

[tomasz-tylenda-sonarsource]

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[hashicorp-vault-sonar-prod]

SONARJAVA-5730

[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
85.7% Coverage on New Code
0.0% Duplication on New Code

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[github-actions]

This PR is stale because it has been open 7 days with no activity. If there is no activity in the next 7 days it will be closed automatically

[sonar-review-alpha]

Summary

Fixes rule S1301 to not recommend converting switch statements to if statements when switching over enums without a default case. When an enum adds a new constant, a switch statement will fail to compile if the new case isn't handled, providing important safety feedback. Converting to if statements loses this safety net. The fix detects enum switches and skips the rule violation if no default case exists.

What reviewers should know

Start with SwitchAtLeastThreeCasesCheck.java to see the core logic: the check now exits early if it detects an enum switch without a default case. The key insight is that semantic analysis (symbolType().symbol().isEnum()) is used to identify enums—pay attention to how the new helper containsDefaultLabel() works and the comment explaining the rationale. The test file shows the expected behavior: small enum switches should not trigger issues (cases 1 & 2), but those with a default case should still be flagged (case 3). Note that the test suite includes a test_without_semantic() which verifies the check still works safely when semantic information is unavailable.

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[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[sonar-review-alpha]

Conclusion: The rule logic is sound and the motivation is clear, but the without-semantic test is broken and will fail.

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[sonar-review-alpha]

This test will fail. Without semantic, switchStatementTree.expression().symbolType().symbol().isEnum() returns false (unknown type resolves to a non-enum symbol), so the new enum guard never fires. The rule then reports issues on switchOverSmallEnum1 and switchOverSmallEnum2 — both have count < 3, no default, and no // Noncompliant annotation — which causes verifyIssues() to fail with unexpected issues.

This test needs its own sample file (or inline source) that reflects the actual without-semantic behavior: either mark those two methods // Noncompliant in a copy of the fixture, or restrict the without-semantic file to the non-enum cases from the original fixture.

• Mark as noise