SONARJAVA-6716: Fix FN in S8909 for classes with explicit constructors but no no-arg constructor

java-checks-test-sources/default/src/main/java/checks/quarkus/CacheKeyGeneratorInstantiableCheckSample.java

@@ -99,6 +99,20 @@ public Object generate(Method method, Object... methodParams) {
   }
 }
 
+class NoncompliantPublicWithExplicitConstructor implements CacheKeyGenerator { // Noncompliant
+//    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  private final ConfigService configService;
+
+  public NoncompliantPublicWithExplicitConstructor(ConfigService configService) {
+    this.configService = configService;
+  }
+
+  @Override
+  public Object generate(Method method, Object... methodParams) {
+    return configService.getPrefix() + methodParams[0];
+  }
+}
+
 class NoncompliantPackagePrivateImplicitConstructor implements CacheKeyGenerator { // Noncompliant
 //    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   @Override
@@ -107,6 +121,20 @@ public Object generate(Method method, Object... methodParams) {
   }
 }
 
+public class CacheKeyGeneratorInstantiableCheckSample implements CacheKeyGenerator { // Noncompliant
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  private final String prefix;
+
+  public CacheKeyGeneratorInstantiableCheckSample(String prefix) {
+    this.prefix = prefix;
+  }
+
+  @Override
+  public Object generate(Method method, Object... methodParams) {
+    return prefix + methodParams[0];
+  }
+}
+
 class CompliantExplicitNoArgsConstructor implements CacheKeyGenerator {
   public CompliantExplicitNoArgsConstructor() {}
 

java-checks/src/main/java/org/sonar/java/checks/quarkus/CacheKeyGeneratorInstantiableCheck.java

@@ -95,12 +95,17 @@ private static boolean matchesAnnotation(AnnotationTree annotationTree, String f
 
   private static boolean hasPublicNoArgsConstructor(ClassTree classTree) {
     Collection<Symbol> constructors = classTree.symbol().lookupSymbols("<init>");
+    if (constructors.isEmpty()) {
+      // No explicit constructors: the compiler generates an implicit no-arg constructor
+      // with the same visibility as the class.
+      return classTree.symbol().isPublic();
+    }
     return constructors.stream()
       .map(Symbol.MethodSymbol.class::cast)
       .filter(CacheKeyGeneratorInstantiableCheck::isNoArgConstructor)
       .findFirst()
       .map(Symbol::isPublic)
-      .orElse(classTree.symbol().isPublic());
+      .orElse(false);
   }
 
   private static boolean isNoArgConstructor(Symbol.MethodSymbol constructor) {