SONARJAVA-6827: Implement S9357 Anonymous classes on functional interfaces should be lambdas by romainbrenguier · Pull Request #5995 · SonarSource/sonar-java

romainbrenguier · 2026-08-21T15:38:49Z

Summary

Implements rule S9357 which detects anonymous inner classes implementing functional interfaces that can be replaced with lambda expressions
Mirrors the detection logic of existing rule S1604 (AnonymousClassShouldBeLambdaCheck) but with scope "All" (main + test code) instead of "Main" only
Includes comprehensive test coverage for noncompliant patterns (simple SAM, inherited interfaces, redeclared methods) and compliant patterns (abstract classes, this usage, checked exceptions, annotations, default methods, recursion, generic methods, enum constants)

Test plan

Unit tests pass with semantic analysis (Java 8)
Unit tests pass without semantic analysis
CI pipeline passes
Ruling tests verify no unexpected regressions

🤖 Generated with Claude Code

…faces should be lambdas Detects anonymous inner classes implementing functional interfaces (single abstract method) that can be replaced with lambda expressions. Mirrors the detection logic of S1604 but applies to all code (main and test scope). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hashicorp-vault-sonar-prod · 2026-08-21T15:39:01Z

SONARJAVA-6827

gitar-bot · 2026-08-21T15:41:27Z

+public class AnonymousClassOnFunctionalInterfaceCheck extends BaseTreeVisitor implements JavaFileScanner, JavaVersionAwareVisitor {
+
+  private static final String JAVA_LANG_OBJECT = "java.lang.Object";
+  private JavaFileScannerContext context;
+  private final Set<IdentifierTree> enumConstants = new HashSet<>();
+
+  @Override
+  public boolean isCompatibleWithJavaVersion(JavaVersion version) {
+    return version.isJava8Compatible();
+  }
+
+  @Override
+  public void scanFile(JavaFileScannerContext context) {
+    this.context = context;
+    enumConstants.clear();


⚠️ Quality: New check duplicates S1604 logic verbatim

AnonymousClassOnFunctionalInterfaceCheck is a byte-for-byte copy of AnonymousClassShouldBeLambdaCheck (S1604), differing only in the @rule key and class name. This duplicates ~150 lines including the UsesThisInstanceVisitor, isSAM/hasSingleAbstractMethodInHierarchy logic, so any future bug fix or improvement must be applied twice and will drift. Extract the shared detection logic into a common base/utility class that both S1604 and S9357 delegate to, so the two rules only differ in their @rule key and scope metadata.

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gitar-bot · 2026-08-21T15:41:28Z

+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-9357",
+  "sqKey": "S9357",
+  "scope": "All",


⚠️ Bug: S9357 double-reports with S1604 on main code

S9357 has scope "All" (main + test) while S1604 has scope "Main", and both implement identical detection with an identical message. When both rules are active in a quality profile, every anonymous-class-to-lambda opportunity in main code will be flagged twice (once as S1604, once as S9357), producing duplicate issues for users. Confirm this is intended; if S9357 is only meant to extend S1604's coverage to test code, its scope/activation should avoid overlapping with S1604 on main code (or S1604 should be deprecated in favor of S9357).

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gitar-bot · 2026-08-21T15:41:30Z

CI failed: Integration test failures in JavaRulingTest due to issue differences (42 differences on Windows and diff reports on Linux) caused by the newly introduced rule S9357.

Overview

All 3 analyzed CI logs across Linux and Windows runners failed during the ruling integration tests (JavaRulingTest) because introducing the new rule S9357 ("Anonymous classes on functional interfaces should be lambdas") produced a mismatch between the actual analysis results and the expected reference outputs.

Failures

Ruling Integration Test Mismatch (confidence: high)

Type: test
Affected jobs: 96823725977, 96823725988, 96823725984
Related to change: yes
Root cause: The new rule S9357 flags anonymous classes that can be converted to lambdas across the ruling integration test suite, causing 42 issue differences and test assertions to fail against the outdated expected test resources.
Suggested fix: Review the generated diff reports and update the expected test resources/dumps in its/ruling/src/test/resources to incorporate the new findings for rule S9357.

Summary

Change-related failures: 3 integration test failures directly caused by the new rule implementation producing different analysis output than expected.
Infrastructure/flaky failures: None.
Recommended action: Verify the correctness of the findings produced by rule S9357 and update the ruling test reference files accordingly.

Code Review ⚠️ Changes requested 0 resolved / 2 findings

Implements rule S9357 to detect anonymous classes on functional interfaces, but AnonymousClassOnFunctionalInterfaceCheck duplicates S1604 logic verbatim and double-reports on main code.

⚠️

Quality: New check duplicates S1604 logic verbatim

📄 java-checks/src/main/java/org/sonar/java/checks/AnonymousClassOnFunctionalInterfaceCheck.java:43-57

AnonymousClassOnFunctionalInterfaceCheck is a byte-for-byte copy of AnonymousClassShouldBeLambdaCheck (S1604), differing only in the @Rule key and class name. This duplicates ~150 lines including the UsesThisInstanceVisitor, isSAM/hasSingleAbstractMethodInHierarchy logic, so any future bug fix or improvement must be applied twice and will drift. Extract the shared detection logic into a common base/utility class that both S1604 and S9357 delegate to, so the two rules only differ in their @Rule key and scope metadata.

⚠️

Bug: S9357 double-reports with S1604 on main code

📄 sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S9357.json:17 📄 java-checks/src/main/java/org/sonar/java/checks/AnonymousClassOnFunctionalInterfaceCheck.java:74-76

S9357 has scope "All" (main + test) while S1604 has scope "Main", and both implement identical detection with an identical message. When both rules are active in a quality profile, every anonymous-class-to-lambda opportunity in main code will be flagged twice (once as S1604, once as S9357), producing duplicate issues for users. Confirm this is intended; if S9357 is only meant to extend S1604's coverage to test code, its scope/activation should avoid overlapping with S1604 on main code (or S1604 should be deprecated in favor of S9357).

🤖 Prompt for agents

Code Review: Implements rule S9357 to detect anonymous classes on functional interfaces, but AnonymousClassOnFunctionalInterfaceCheck duplicates S1604 logic verbatim and double-reports on main code.

1. ⚠️ Quality: New check duplicates S1604 logic verbatim
   Files: java-checks/src/main/java/org/sonar/java/checks/AnonymousClassOnFunctionalInterfaceCheck.java:43-57

   AnonymousClassOnFunctionalInterfaceCheck is a byte-for-byte copy of AnonymousClassShouldBeLambdaCheck (S1604), differing only in the @Rule key and class name. This duplicates ~150 lines including the UsesThisInstanceVisitor, isSAM/hasSingleAbstractMethodInHierarchy logic, so any future bug fix or improvement must be applied twice and will drift. Extract the shared detection logic into a common base/utility class that both S1604 and S9357 delegate to, so the two rules only differ in their @Rule key and scope metadata.

2. ⚠️ Bug: S9357 double-reports with S1604 on main code
   Files: sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S9357.json:17, java-checks/src/main/java/org/sonar/java/checks/AnonymousClassOnFunctionalInterfaceCheck.java:74-76

   S9357 has scope "All" (main + test) while S1604 has scope "Main", and both implement identical detection with an identical message. When both rules are active in a quality profile, every anonymous-class-to-lambda opportunity in main code will be flagged twice (once as S1604, once as S9357), producing duplicate issues for users. Confirm this is intended; if S9357 is only meant to extend S1604's coverage to test code, its scope/activation should avoid overlapping with S1604 on main code (or S1604 should be deprecated in favor of S9357).

Implementation Status ✅ 1 / 1 issues implemented

✅ SONARJAVA-6827 — 1 / 1 objectives

The PR successfully implements the S9357 rule checking for anonymous classes on functional interfaces that should be lambdas, including the rule implementation, rule metadata, localization files, and corresponding test cases.

✅ 1 complete

✅ Implement rule S9357 to detect anonymous classes on functional interfaces that should be lambdas

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datadog-sonarsource · 2026-08-21T15:45:29Z

⚠️ Warnings

🚦 4 Pipeline jobs failed

Build | Ruling QA (warp-custom-ubuntu-24-04, only-sonarqube-project, LATEST_RELEASE)

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1 failed test. AssertionError: Expecting empty but was: "Issues differences: 42" in JavaRulingTest.sonarqube_server.

Build | Ruling QA (warp-custom-ubuntu-24-04, without-sonarqube-project, LATEST_RELEASE)

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4 failed tests due to assertion errors indicating issues differences: 9, 35, 2, and 84

Build | Ruling QA (warp-custom-windows-2022-l, without-sonarqube-project, LATEST_RELEASE)

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4 failed tests in JavaRulingTest due to assertion errors: issues differences not empty.

View all 4 failed jobs.

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🔗 Commit SHA: d439596 | Docs | View more details | Give us feedback!}

sonarqube-next · 2026-08-21T15:46:51Z

Quality Gate failed

Failed conditions
54.7% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube

github-actions · 2026-08-21T15:54:03Z

❌ Ruling needs updating. A fix PR has been created: #5996

Please review and merge it into your branch.

gitar-bot Bot reviewed Aug 21, 2026

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github-actions Bot mentioned this pull request Aug 21, 2026

Update ruling results for PR #5995 #5996

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SONARJAVA-6827: Implement S9357 Anonymous classes on functional interfaces should be lambdas - #5995

SONARJAVA-6827: Implement S9357 Anonymous classes on functional interfaces should be lambdas#5995
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Overview

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Ruling Integration Test Mismatch (confidence: high)

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Overview

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Ruling Integration Test Mismatch (confidence: high)

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