Allow IPropertyValueConverter to determine if a property has value

src/Umbraco.Core/Models/PublishedContent/PublishedPropertyType.cs

@@ -77,7 +77,7 @@ namespace Umbraco.Core.Models.PublishedContent
 
         /// <summary>
         /// Gets the published content type containing the property type.
-        /// </summary>        
+        /// </summary>
         public PublishedContentType ContentType { get; internal set; } // internally set by PublishedContentType constructor
 
         /// <summary>
@@ -193,6 +193,20 @@ namespace Umbraco.Core.Models.PublishedContent
             _modelClrType = _converter == null ? typeof (object) : _converter.GetPropertyValueType(this);
         }
 
+        /// <summary>
+        /// Determines whether a source value is an actual value, or not a value.
+        /// </summary>
+        /// <remarks>Used by property.HasValue and, for instance, in fallback scenarios.</remarks>
+        public bool IsValue(object value)
+        {
+            // if we have a converter, use the converter,
+            // otherwise use the old magic null & string comparisons
+
+            return _converter == null
+                ? value != null && (!(value is string) || string.IsNullOrWhiteSpace((string) value) == false)
+                : _converter.IsValue(value);
+        }
+
         /// <summary>
         /// Gets the property cache level.
         /// </summary>

src/Umbraco.Core/PropertyEditors/IPropertyValueConverter.cs

@@ -17,6 +17,11 @@ namespace Umbraco.Core.PropertyEditors
         /// <returns>A value indicating whether the converter supports a property type.</returns>
         bool IsConverter(PublishedPropertyType propertyType);
 
+        /// <summary>
+        /// Determines whether a source value is an actual value, or not a value.
+        /// </summary>
+        bool IsValue(object value);
+
         /// <summary>
         /// Gets the type of values returned by the converter.
         /// </summary>

src/Umbraco.Core/PropertyEditors/PropertyValueConverterBase.cs

@@ -9,33 +9,24 @@ namespace Umbraco.Core.PropertyEditors
     public abstract class PropertyValueConverterBase : IPropertyValueConverter
     {
         public virtual bool IsConverter(PublishedPropertyType propertyType)
-        {
-            return false;
-        }
+            => false;
+
+        public bool IsValue(object value)
+            => value != null && (!(value is string) || string.IsNullOrWhiteSpace((string) value) == false);
 
         public virtual Type GetPropertyValueType(PublishedPropertyType propertyType)
-        {
-            return typeof (object);
-        }
+            => typeof (object);
 
         public virtual PropertyCacheLevel GetPropertyCacheLevel(PublishedPropertyType propertyType)
-        {
-            return PropertyCacheLevel.Snapshot;
-        }
+            => PropertyCacheLevel.Snapshot;
 
         public virtual object ConvertSourceToIntermediate(IPublishedElement owner, PublishedPropertyType propertyType, object source, bool preview)
-        {
-            return source;
-        }
+            => source;
 
         public virtual object ConvertIntermediateToObject(IPublishedElement owner, PublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object inter, bool preview)
-        {
-            return inter;
-        }
+            => inter;
 
         public virtual object ConvertIntermediateToXPath(IPublishedElement owner, PublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object inter, bool preview)
-        {
-            return inter?.ToString() ?? string.Empty;
-        }
+            => inter?.ToString() ?? string.Empty;
     }
 }

src/Umbraco.Tests/Published/ConvertersTests.cs

@@ -47,6 +47,9 @@ namespace Umbraco.Tests.Published
 
         private class SimpleConverter1 : IPropertyValueConverter
         {
+            public bool IsValue(object value)
+                => value != null && (!(value is string) || string.IsNullOrWhiteSpace((string) value) == false);
+
             public bool IsConverter(PublishedPropertyType propertyType)
                 => propertyType.EditorAlias.InvariantEquals("Umbraco.Void");
 
@@ -117,6 +120,9 @@ namespace Umbraco.Tests.Published
                 _cacheLevel = cacheLevel;
             }
 
+            public bool IsValue(object value)
+                => value != null && (!(value is string) || string.IsNullOrWhiteSpace((string) value) == false);
+
             public bool IsConverter(PublishedPropertyType propertyType)
                 => propertyType.EditorAlias.InvariantEquals("Umbraco.Void");
 

src/Umbraco.Tests/Published/PropertyCacheLevelTests.cs

@@ -210,6 +210,9 @@ namespace Umbraco.Tests.Published
             public int SourceConverts { get; private set; }
             public int InterConverts { get; private set; }
 
+            public bool IsValue(object value)
+                => value != null && (!(value is string) || string.IsNullOrWhiteSpace((string) value) == false);
+
             public bool IsConverter(PublishedPropertyType propertyType)
                 => propertyType.EditorAlias.InvariantEquals("Umbraco.Void");
 
@@ -235,4 +238,4 @@ namespace Umbraco.Tests.Published
                 => ((int) inter).ToString();
         }
     }
-}
+}

src/Umbraco.Web/PublishedCache/NuCache/Property.cs

@@ -90,11 +90,7 @@ namespace Umbraco.Web.PublishedCache.NuCache
         public override bool HasValue(string culture = null, string segment = null)
         {
             ContextualizeVariation(ref culture, ref segment);
-
-            var sourceValue = GetSourceValue(culture, segment);
-
-            return sourceValue != null &&
-                   (!(sourceValue is string) || string.IsNullOrWhiteSpace((string) sourceValue) == false);
+            return PropertyType.IsValue(GetSourceValue(culture, segment));
         }
 
         // used to cache the CacheValues of this property