SONARJAVA-5983 Do not raise S1220 on compact source files (#5417)

Author: tomasz-tylenda-sonarsource

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

@@ -0,0 +1,7 @@
+void main() {
+  System.out.println("Hello from compact source!");
+}
+
+int value = 1;
+
+void helper() {}

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

@@ -20,6 +20,9 @@
 import org.sonar.plugins.java.api.JavaFileScanner;
 import org.sonar.plugins.java.api.JavaFileScannerContext;
 import org.sonar.plugins.java.api.tree.CompilationUnitTree;
+import org.sonar.plugins.java.api.tree.Tree;
+
+import java.util.List;
 
 @Rule(key = "S1220")
 public class DefaultPackageCheck implements JavaFileScanner {
@@ -28,10 +31,14 @@ public class DefaultPackageCheck implements JavaFileScanner {
   public void scanFile(JavaFileScannerContext context) {
     if (context.fileParsed()) {
       CompilationUnitTree cut = context.getTree();
-      if (cut.moduleDeclaration() == null && cut.packageDeclaration() == null) {
+      if (cut.moduleDeclaration() == null && cut.packageDeclaration() == null && !isCompactSource(cut)) {
         context.addIssueOnFile(this, "Move this file to a named package.");
       }
     }
   }
 
+  private static boolean isCompactSource(CompilationUnitTree cu) {
+    List<Tree> types = cu.types();
+    return types.size() == 1 && types.get(0).is(Tree.Kind.IMPLICIT_CLASS);
+  }
 }

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

@@ -47,4 +47,11 @@ void with_module() {
       .verifyNoIssues();
   }
 
+  @Test
+  void compact_source() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/DefaultPackageCheckCompactSample.java"))
+      .withCheck(new DefaultPackageCheck())
+      .verifyNoIssues();
+  }
 }