V13: Ensure TransformingIndexValues event is also raised from the DeliveryApiContentIndex (#16756)

* Removing override of OnTransformingIndexValues from DeliveryApiContentIndex

* Making sure that TransformingIndexValues event is raised for DeliveryApiContentIndex without performing the special index value transformations

* Review suggestion

src/Umbraco.Examine.Lucene/DeliveryApiContentIndex.cs

@@ -17,6 +17,9 @@ public class DeliveryApiContentIndex : UmbracoExamineIndex
     private readonly IDeliveryApiCompositeIdHandler _deliveryApiCompositeIdHandler;
     private readonly ILogger<DeliveryApiContentIndex> _logger;
 
+    // The special path and icon value transformations are not needed in this case
+    protected override bool ApplySpecialValueTransformations => false;
+
     [Obsolete("Use the constructor that takes an IDeliveryApiCompositeIdHandler instead, scheduled for removal in v15")]
     public DeliveryApiContentIndex(
         ILoggerFactory loggerFactory,
@@ -134,10 +137,4 @@ public class DeliveryApiContentIndex : UmbracoExamineIndex
 
         return (compositeIdModel.Id?.ToString(CultureInfo.InvariantCulture), compositeIdModel.Culture);
     }
-
-    protected override void OnTransformingIndexValues(IndexingItemEventArgs e)
-    {
-        // UmbracoExamineIndex (base class down the hierarchy) performs some magic transformations here for paths and icons;
-        // we don't want that for the Delivery API, so we'll have to override this method and simply do nothing.
-    }
 }

src/Umbraco.Examine.Lucene/UmbracoExamineIndex.cs

@@ -38,8 +38,14 @@ public abstract class UmbracoExamineIndex : LuceneIndex, IUmbracoIndex, IIndexDi
     }
 
     public Attempt<string?> IsHealthy() => _diagnostics.IsHealthy();
+
     public virtual IReadOnlyDictionary<string, object?> Metadata => _diagnostics.Metadata;
 
+    /// <summary>
+    ///     Performs special __Path and __Icon value transformations to all deriving indexes when set to true.
+    /// </summary>
+    protected virtual bool ApplySpecialValueTransformations => true;
+
     /// <summary>
     ///     When set to true Umbraco will keep the index in sync with Umbraco data automatically
     /// </summary>
@@ -115,16 +121,27 @@ public abstract class UmbracoExamineIndex : LuceneIndex, IUmbracoIndex, IIndexDi
     {
         base.OnTransformingIndexValues(e);
 
+        if (ApplySpecialValueTransformations)
+        {
+            ApplySpecialIndexValueTransformations(e);
+        }
+    }
+
+    /// <summary>
+    ///     Updates the index ValueSet with a special __Path and __Icon fields.
+    /// </summary>
+    private void ApplySpecialIndexValueTransformations(IndexingItemEventArgs e)
+    {
         var updatedValues = e.ValueSet.Values.ToDictionary(x => x.Key, x => (IEnumerable<object>)x.Value);
 
-        //ensure special __Path field
+        // Ensure special __Path field
         var path = e.ValueSet.GetValue("path");
         if (path != null)
         {
             updatedValues[UmbracoExamineFieldNames.IndexPathFieldName] = path.Yield();
         }
 
-        //icon
+        // Ensure special __Icon field
         if (e.ValueSet.Values.TryGetValue("icon", out IReadOnlyList<object>? icon) &&
             e.ValueSet.Values.ContainsKey(UmbracoExamineFieldNames.IconFieldName) == false)
         {