S2325 Do not report on instance main.

Author: tomasz-tylenda-sonarsource

java-checks-test-sources/default/src/main/java/checks/StaticMethodCheckCompactSample.java

@@ -0,0 +1,3 @@
+void main() {
+  System.out.println("Hello, World!");
+}

java-checks-test-sources/default/src/main/java/checks/StaticMethodCheckSample.java

@@ -426,3 +426,20 @@ private List<List<T>> requiresNestedTypeVar() { // Compliant
     }
   }
 }
+
+// Note `final` on the class indicating that main methods will not be overridden.
+// Without it, the check would apply only to private methods.
+final public class StaticMethodCheckSample {
+  void main() { // Compliant
+    System.out.println("StaticMethodCheckSample no arg main");
+  }
+
+  void main(String[] args) { // Compliant
+    System.out.println("StaticMethodCheckSample main with args");
+  }
+
+  // Intentional FN to keep things simple.
+  void main(int i) { // Compliant
+    System.out.println("i = " + i);
+  }
+}

java-checks/src/main/java/org/sonar/java/checks/StaticMethodCheck.java

@@ -160,13 +160,18 @@ private static boolean shouldBePlacedAfterStatic(Modifier modifier) {
   }
 
   private static boolean isExcluded(MethodTree tree) {
-    return tree.is(Tree.Kind.CONSTRUCTOR) || EXCLUDED_SERIALIZABLE_METHODS.matches(tree) || hasEmptyBody(tree);
+    return tree.is(Tree.Kind.CONSTRUCTOR) || EXCLUDED_SERIALIZABLE_METHODS.matches(tree) || hasEmptyBody(tree) || isInstanceMain(tree);
   }
 
   private static boolean hasEmptyBody(MethodTree tree) {
     return tree.block() != null && tree.block().body().isEmpty();
   }
 
+  private static boolean isInstanceMain(MethodTree tree) {
+    // For simplicity check only the name.
+    return "main".equals(tree.simpleName().toString());
+  }
+
   @Override
   public void visitIdentifier(IdentifierTree tree) {
     super.visitIdentifier(tree);

java-checks/src/test/java/org/sonar/java/checks/StaticMethodCheckTest.java

@@ -32,6 +32,14 @@ void test() {
       .verifyIssues();
   }
 
+  @Test
+  void test_compact_source() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/StaticMethodCheckCompactSample.java"))
+      .withCheck(new StaticMethodCheck())
+      .verifyNoIssues();
+  }
+
   @Test
   void test_non_compiling() {
     CheckVerifier.newVerifier()