Updated Review comments - covered edge case with deletion of property

src/main/java/io/wcm/caconfig/extensions/persistence/impl/PagePersistenceStrategy.java

@@ -211,7 +211,7 @@ public boolean persistConfigurationCollection(@NotNull ResourceResolver resolver
     // create new or overwrite existing children
     for (ConfigurationPersistData item : data.getItems()) {
       String path = getCollectionItemResourcePath(parentPath + "/" + item.getCollectionItemName());
-      if (isItemModifiedOrNewlyAdded(resolver, path, item)) {
+      if (isItemModifiedOrNewlyAdded(resolver, path, item, configurationManagementSettings)) {
         ensureContainingPage(resolver, path, resourceType, configurationManagementSettings);
         getOrCreateResource(resolver, path, DEFAULT_CONFIG_NODE_TYPE, item.getProperties(), configurationManagementSettings);
         updatePageLastMod(resolver, pageManager, path);

src/main/java/io/wcm/caconfig/extensions/persistence/impl/PersistenceUtils.java

@@ -285,29 +285,31 @@ public static void commit(ResourceResolver resourceResolver, String relatedResou
   /**
    * Checks if the given item is modified or newly added by comparing its properties with the current state of the resource.
    *
-   * @param resolver The ResourceResolver to access the resource.
+   * @param resolver     The ResourceResolver to access the resource.
    * @param resourcePath The path of the resource to compare against.
-   * @param item The ConfigurationPersistData item containing the properties to compare.
+   * @param item         The ConfigurationPersistData item containing the properties to compare.
+   * @param settings     The ConfigurationManagementSettings to determine which properties to ignore.
    * @return true if the resource does not exist or if any property value differs, false otherwise.
    */
-  public static boolean isItemModifiedOrNewlyAdded(ResourceResolver resolver, String resourcePath, ConfigurationPersistData item) {
+  public static boolean isItemModifiedOrNewlyAdded(ResourceResolver resolver, String resourcePath, ConfigurationPersistData item, ConfigurationManagementSettings settings) {
     Resource resource = resolver.getResource(resourcePath);
     if (resource == null) {
       return true; // Resource does not exist, so it is considered modified
     }
+    ValueMap valueMap = resource.getValueMap();
+    Map<String, Object> currentProperties = new HashMap<>(valueMap);
+    Map<String, Object> newProperties = new HashMap<>(item.getProperties());
 
-    ValueMap currentProperties = resource.getValueMap();
-    Map<String, Object> itemProperties = item.getProperties();
+    // Filter out ignored properties
+    Set<String> currentPropertyNames = new HashSet<>(currentProperties.keySet());
+    PropertiesFilterUtil.removeIgnoredProperties(currentPropertyNames, settings);
+    currentProperties.keySet().retainAll(currentPropertyNames);
 
-    for (Map.Entry<String, Object> entry : itemProperties.entrySet()) {
-      String key = entry.getKey();
-      Object value = entry.getValue();
-      if (!value.equals(currentProperties.get(key))) {
-        return true; // Property value differs
-      }
-    }
+    Set<String> newPropertyNames = new HashSet<>(newProperties.keySet());
+    PropertiesFilterUtil.removeIgnoredProperties(newPropertyNames, settings);
+    newProperties.keySet().retainAll(newPropertyNames);
 
-    return false; // No differences found
+    return !currentProperties.equals(newProperties);
   }
 
   /**

src/test/java/io/wcm/caconfig/extensions/persistence/impl/PagePersistenceStrategyTest.java

@@ -30,6 +30,9 @@
 import java.util.Calendar;
 import java.util.List;
 
+import org.apache.sling.api.resource.PersistenceException;
+import org.apache.sling.api.resource.Resource;
+import org.apache.sling.api.resource.ResourceResolver;
 import org.apache.sling.caconfig.ConfigurationBuilder;
 import org.apache.sling.caconfig.management.ConfigurationManager;
 import org.apache.sling.hamcrest.ResourceMatchers;
@@ -161,6 +164,38 @@ void testListConfig() {
     assertEquals(234, config2.intParam());
   }
 
+  @Test
+  void testListConfig_updateLastModifiedIfPropertyRemoved() throws PersistenceException {
+    context.registerInjectActivateService(new PagePersistenceStrategy(), "enabled", true);
+    ResourceResolver resourceResolver = context.resourceResolver();
+
+
+    // write config
+    writeConfigurationCollection(context, contentPage.getPath(), ListConfig.class.getName(), List.of(
+            ImmutableValueMap.of("stringParam", "value1", "intParam", 123),
+            ImmutableValueMap.of("stringParam", "value2", "intParam", 234)
+    ));
+
+    // assert storage in page in /conf
+    Page parentPage = context.pageManager().getPage("/conf/test/site1/sling:configs/" + ListConfig.class.getName());
+    assertNotNull(parentPage);
+
+    Page configPage1 = context.pageManager().getPage("/conf/test/site1/sling:configs/" + ListConfig.class.getName() + "/item0");
+    assertThat(configPage1.getContentResource(), ResourceMatchers.props("stringParam", "value1", "intParam", 123));
+
+    Page configPage2 = context.pageManager().getPage("/conf/test/site1/sling:configs/" + ListConfig.class.getName() + "/item1");
+    assertThat(configPage2.getContentResource(), ResourceMatchers.props("stringParam", "value2", "intParam", 234));
+
+    writeConfigurationCollection(context, contentPage.getPath(), ListConfig.class.getName(), List.of(
+            ImmutableValueMap.of("stringParam", "value1", "intParam", 123),
+            ImmutableValueMap.of("stringParam", "value2")
+    ));
+    Calendar lastModifiedConfigPage2AfterUpdate = configPage2.getContentResource().getValueMap().get(PN_LAST_MOD, Calendar.class);
+    System.out.println(lastModifiedConfigPage2AfterUpdate);
+    //ConfigPage2 last modified date should be updated because it is updated
+      assertNotNull(lastModifiedConfigPage2AfterUpdate);
+  }
+
   @Test
   void testListConfig_Nested() {
     context.registerInjectActivateService(new PagePersistenceStrategy(), "enabled", true);