SONARJAVA-6075 Do not raise S2325 on instance main (#5421)

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 +426,19 @@ 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");
+  }
+
+  void main(int i) { // Noncompliant
+    System.out.println("i = " + i);
+  }
+}

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

@@ -64,6 +64,14 @@ public class StaticMethodCheck extends BaseTreeVisitor implements JavaFileScanne
       .addWithoutParametersMatcher()
       .build());
 
+  private static final MethodMatchers MAIN_METHOD =
+    MethodMatchers.create()
+      .ofAnyType()
+      .names("main")
+      .addParametersMatcher(params ->
+        params.isEmpty() || (params.size() == 1 && params.get(0).isSubtypeOf("java.lang.String[]")))
+      .build();
+
   private JavaFileScannerContext context;
   private Deque<MethodReference> methodReferences = new LinkedList<>();
 
@@ -160,7 +168,7 @@ 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) || MAIN_METHOD.matches(tree);
   }
 
   private static boolean hasEmptyBody(MethodTree 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()