fix(controller): do not propagate NonNullApi to other packages

packages/java/endpoint/src/main/java/com/vaadin/hilla/ExplicitNullableTypeChecker.java

@@ -124,15 +124,13 @@ public String checkValueForAnnotatedElement(Object value,
         }
         if (annotatedElement instanceof Method) {
             return checkValueForType(value,
-                    ((Method) annotatedElement).getGenericReturnType(),
-                    requiredByContext);
+                    ((Method) annotatedElement).getGenericReturnType());
         }
         return null;
     }
 
-    String checkValueForType(Object value, Type expectedType,
-            boolean requiredByContext) {
-        return new ExplicitNullableTypeCheckerHelper(requiredByContext)
-                .checkValueForType(value, expectedType);
+    String checkValueForType(Object value, Type expectedType) {
+        return new ExplicitNullableTypeCheckerHelper().checkValueForType(value,
+                expectedType);
     }
 }

packages/java/endpoint/src/main/java/com/vaadin/hilla/ExplicitNullableTypeCheckerHelper.java

@@ -38,6 +38,7 @@
 import com.vaadin.hilla.parser.utils.Generics;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.lang.NonNullApi;
 
 import static com.vaadin.hilla.ExplicitNullableTypeChecker.isRequired;
 
@@ -49,22 +50,10 @@ class ExplicitNullableTypeCheckerHelper {
     // A map for tracking already visited Beans.
     private Map<Type, Set<Object>> visitedBeans;
 
-    private boolean requiredByContext;
-
     private static Logger getLogger() {
         return LoggerFactory.getLogger(EndpointController.class);
     }
 
-    /**
-     * Creates a new helper.
-     *
-     * @param requiredByContext
-     *            {@code true} if the context defines that the node is required
-     */
-    public ExplicitNullableTypeCheckerHelper(boolean requiredByContext) {
-        this.requiredByContext = requiredByContext;
-    }
-
     /**
      * Check if the Bean value and type have been visited.
      */
@@ -208,10 +197,14 @@ private String checkBeanFields(Object value, Type expectedType) {
         }
         markAsVisited(value, expectedType);
         Class<?> clazz = (Class<?>) expectedType;
+        // the context is the package where the object is defined
+        boolean requiredByContext = clazz.getPackage() != null
+                && clazz.getPackage().isAnnotationPresent(NonNullApi.class);
         try {
             for (PropertyDescriptor propertyDescriptor : Introspector
                     .getBeanInfo(clazz).getPropertyDescriptors()) {
-                if (!isPropertySubjectForChecking(propertyDescriptor)) {
+                if (!isPropertySubjectForChecking(propertyDescriptor,
+                        requiredByContext)) {
                     continue;
                 }
 
@@ -239,7 +232,7 @@ private String checkBeanFields(Object value, Type expectedType) {
     }
 
     private boolean isPropertySubjectForChecking(
-            PropertyDescriptor propertyDescriptor) {
+            PropertyDescriptor propertyDescriptor, boolean requiredByContext) {
         try {
             String name = propertyDescriptor.getName();
             Method readMethod = propertyDescriptor.getReadMethod();

packages/java/endpoint/src/test/java/com/vaadin/hilla/EndpointControllerTest.java

@@ -36,7 +36,6 @@
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 import org.junit.rules.TemporaryFolder;
-import org.mockito.ArgumentMatchers;
 import org.mockito.Mockito;
 import org.springframework.boot.autoconfigure.jackson.JacksonProperties;
 import org.springframework.cglib.proxy.Enhancer;
@@ -1128,8 +1127,8 @@ public void should_Invoke_ExplicitNullableTypeChecker()
                 ExplicitNullableTypeChecker.class);
 
         when(explicitNullableTypeChecker.checkValueForType(
-                eq(NullCheckerTestClass.OK_RESPONSE), eq(String.class),
-                eq(false))).thenReturn(null);
+                eq(NullCheckerTestClass.OK_RESPONSE), eq(String.class)))
+                .thenReturn(null);
 
         String testOkMethod = "testOkMethod";
         ResponseEntity<String> response = createVaadinController(
@@ -1445,8 +1444,8 @@ private <T> EndpointController createVaadinController(T endpoint,
         if (explicitNullableTypeChecker == null) {
             explicitNullableTypeChecker = mock(
                     ExplicitNullableTypeChecker.class);
-            when(explicitNullableTypeChecker.checkValueForType(any(), any(),
-                    ArgumentMatchers.anyBoolean())).thenReturn(null);
+            when(explicitNullableTypeChecker.checkValueForType(any(), any()))
+                    .thenReturn(null);
         }
 
         ApplicationContext mockApplicationContext = mockApplicationContext(