Optimize mimetype validation to only run when annotation exists

.gitignore

@@ -31,7 +31,4 @@ cds-feature-attachments/src/test/resources/schema.sql
 .secrets
 event.json
 
-# CAP Notebook
-cap-notebook/demoapp/
-
-.DS_Store
+.DS_Store

cds-feature-attachments/src/main/java/com/sap/cds/feature/attachments/handler/applicationservice/helper/mimeTypeValidation/AttachmentValidationHelper.java

@@ -18,7 +18,6 @@
 import java.util.stream.Collectors;
 
 public final class AttachmentValidationHelper {
-  public static final List<String> WILDCARD_MEDIA_TYPE = List.of("*/*");
   private static AssociationCascader cascader = new AssociationCascader();
 
   static void setCascader(AssociationCascader testCascader) {
@@ -48,9 +47,16 @@ public static void validateMediaAttachments(
       return;
     }
 
-    // validate the media types of the attachments
+    // Resolve which media entities actually have the @Core.AcceptableMediaTypes annotation.
+    // If none do, skip the entire validation – no data extraction, no MIME resolution needed.
     Map<String, List<String>> allowedTypesByElementName =
         MediaTypeResolver.getAcceptableMediaTypesFromEntity(cdsModel, mediaEntityNames);
+
+    if (allowedTypesByElementName.isEmpty()) {
+      return;
+    }
+
+    // validate the media types of the attachments
     Map<String, Set<String>> fileNamesByElementName =
         AttachmentDataExtractor.extractAndValidateFileNamesByElement(entity, data);
     validateAttachmentMediaTypes(fileNamesByElementName, allowedTypesByElementName);
@@ -81,9 +87,12 @@ private static Map<String, List<String>> findInvalidFilesByElementName(
     Map<String, List<String>> invalidFiles = new HashMap<>();
     fileNamesByElementName.forEach(
         (elementName, files) -> {
-          // Resolve the allowed media types for this field / element.
-          List<String> acceptableTypes =
-              acceptableMediaTypesByElementName.getOrDefault(elementName, WILDCARD_MEDIA_TYPE);
+          // Only validate elements that have the @Core.AcceptableMediaTypes annotation.
+          // Elements not in the map are unconstrained and can accept any media type.
+          List<String> acceptableTypes = acceptableMediaTypesByElementName.get(elementName);
+          if (acceptableTypes == null) {
+            return;
+          }
 
           // Filter out files whose media type is NOT allowed for this element
           List<String> invalid =
@@ -113,10 +122,7 @@ private static ServiceException buildUnsupportedFileTypeMessage(
                   String element = entry.getKey();
                   String files = String.join(", ", entry.getValue());
                   String allowed =
-                      String.join(
-                          ", ",
-                          acceptableMediaTypesByElementName.getOrDefault(
-                              element, WILDCARD_MEDIA_TYPE));
+                      String.join(", ", acceptableMediaTypesByElementName.get(element));
                   return files + " (allowed: " + allowed + ") ";
                 })
             .collect(Collectors.joining("; "));

cds-feature-attachments/src/main/java/com/sap/cds/feature/attachments/handler/applicationservice/helper/mimeTypeValidation/MediaTypeResolver.java

@@ -27,17 +27,16 @@ public static Map<String, List<String>> getAcceptableMediaTypesFromEntity(
     }
     for (String entityName : mediaEntityNames) {
       CdsEntity mediaEntity = model.getEntity(entityName);
-      result.put(entityName, fetchAcceptableMediaTypes(mediaEntity));
+      fetchAcceptableMediaTypes(mediaEntity).ifPresent(types -> result.put(entityName, types));
     }
 
     return result;
   }
 
-  private static List<String> fetchAcceptableMediaTypes(CdsEntity entity) {
+  private static Optional<List<String>> fetchAcceptableMediaTypes(CdsEntity entity) {
     return getAcceptableMediaTypesAnnotation(entity)
         .map(CdsAnnotation::getValue)
-        .map(value -> objectMapper.convertValue(value, STRING_LIST_TYPE_REF))
-        .orElse(AttachmentValidationHelper.WILDCARD_MEDIA_TYPE);
+        .map(value -> objectMapper.convertValue(value, STRING_LIST_TYPE_REF));
   }
 
   public static Optional<CdsAnnotation<Object>> getAcceptableMediaTypesAnnotation(

cds-feature-attachments/src/test/java/com/sap/cds/feature/attachments/handler/applicationservice/helper/mimeTypeValidation/AttachmentValidationHelperTest.java

@@ -60,6 +60,35 @@ void doesNothing_whenEntityNotFoundInModel() {
     }
   }
 
+  @Test
+  void doesNothing_whenNoEntityHasAcceptableMediaTypesAnnotation() {
+    CdsEntity entity = mockEntity("Entity");
+    CdsRuntime runtime = mockRuntime(entity);
+
+    try (MockedStatic<ApplicationHandlerHelper> helper =
+            mockStatic(ApplicationHandlerHelper.class);
+        MockedStatic<MediaTypeResolver> resolver = mockStatic(MediaTypeResolver.class);
+        MockedStatic<AttachmentDataExtractor> extractor =
+            mockStatic(AttachmentDataExtractor.class)) {
+
+      helper.when(() -> ApplicationHandlerHelper.isMediaEntity(entity)).thenReturn(true);
+
+      // MediaTypeResolver returns empty map = no entity has the annotation
+      resolver
+          .when(
+              () ->
+                  MediaTypeResolver.getAcceptableMediaTypesFromEntity(
+                      any(CdsModel.class), anyList()))
+          .thenReturn(Map.of());
+
+      // Verify that AttachmentDataExtractor is never called (early return)
+      assertDoesNotThrow(
+          () -> AttachmentValidationHelper.validateMediaAttachments(entity, List.of(), runtime));
+
+      extractor.verifyNoInteractions();
+    }
+  }
+
   @Test
   void doesNotThrow_whenNoFiles() {
     CdsEntity entity = mockEntity("Entity");

cds-feature-attachments/src/test/java/com/sap/cds/feature/attachments/handler/applicationservice/helper/mimeTypeValidation/MediaTypeResolverTest.java

@@ -47,7 +47,7 @@ void shouldReturnMediaTypesFromAnnotation() {
   }
 
   @Test
-  void shouldResolveMediaTypesUsingCascader() {
+  void shouldExcludeEntityWithoutAnnotation() {
     CdsModel model = mock(CdsModel.class);
     CdsEntity media = mock(CdsEntity.class);
 
@@ -57,6 +57,7 @@ void shouldResolveMediaTypesUsingCascader() {
     Map<String, List<String>> result =
         MediaTypeResolver.getAcceptableMediaTypesFromEntity(model, List.of("MediaEntity"));
 
-    assertThat(result).containsKey("MediaEntity");
+    assertThat(result).doesNotContainKey("MediaEntity");
+    assertThat(result).isEmpty();
   }
 }