Introduced ResetPermittedContentTypes()

Similar to the previously introduced `ResetAttributeDescriptors()` (b0c5a5e), this exposes a new `internal` helper method, `ResetPermittedContentTypes()`, which is called from `TopicRepositoryBase.Save()` when a `ContentTypeDescriptor` is updated, assuming its relationships have been updated.

In practice, this might be called rarely enough, and may be fast enough to assemble, that we could just do away with the cache entirely. That said, this is a familiar and easy pattern to apply alongside `ResetAttributeDescriptors()`, so we'll stick with this for now.

Also created a corresponding unit test to validate this functionality.

Author: JeremyCaney

OnTopic.Tests/TopicRepositoryBaseTest.cs

@@ -380,6 +380,30 @@ public void Save_ContentTypeDescriptor_UpdatesContentTypeCache() {
 
     }
 
+    /*==========================================================================================================================
+    | TEST: SAVE: CONTENT TYPE DESCRIPTOR: UPDATES PERMITTED CONTENT TYPES
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Loads the <see cref="TopicRepositoryBase.GetContentTypeDescriptors()"/>, then saves an existing <see cref=
+    ///   "ContentTypeDescriptor"/> via <see cref="TopicRepositoryBase.Save(Topic, Boolean, Boolean)"/>, and ensures that
+    ///   it the <see cref="ContentTypeDescriptor.PermittedContentTypes"/> cache is updated.
+    /// </summary>
+    [TestMethod]
+    public void Save_ContentTypeDescriptor_UpdatesPermittedContentTypes() {
+
+      var contentTypes          = _topicRepository.GetContentTypeDescriptors();
+      var pageContentType       = contentTypes.GetTopic("Page");
+      var lookupContentType     = contentTypes.GetTopic("Lookup");
+      var initialCount          = pageContentType.PermittedContentTypes.Count;
+
+      pageContentType.Relationships.SetTopic("ContentTypes", lookupContentType);
+
+      _topicRepository.Save(pageContentType);
+
+      Assert.AreNotEqual<int>(initialCount, pageContentType.PermittedContentTypes.Count);
+
+    }
+
     /*==========================================================================================================================
     | TEST: DELETE: CONTENT TYPE DESCRIPTOR: UPDATES CONTENT TYPE CACHE
     \-------------------------------------------------------------------------------------------------------------------------*/

OnTopic/Metadata/ContentTypeDescriptor.cs

@@ -238,6 +238,21 @@ internal void ResetAttributeDescriptors() {
       }
     }
 
+    /*==========================================================================================================================
+    | METHOD: RESET PERMITTED CONTENT TYPES
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Resets the list of <see cref="ContentTypeDescriptor"/>s stored in the <see cref="PermittedContentTypes"/> collection
+    ///   on this <see cref="ContentTypeDescriptor"/>.
+    /// </summary>
+    /// <remarks>
+    ///   Each <see cref="ContentTypeDescriptor"/> has a <see cref="PermittedContentTypes"/> collection which includes the <see
+    ///   cref="ContentTypeDescriptor"/>s associated with that <see cref="ContentTypeDescriptor"/>. As this is cached, however,
+    ///   the value should be reset whenever a <see cref="ContentTypeDescriptor"/> has been modified, in case those values have
+    ///   changed.
+    /// </remarks>
+    internal void ResetPermittedContentTypes() => _permittedContentTypes = null;
+
     /*==========================================================================================================================
     | METHOD: IS TYPE OF?
     \-------------------------------------------------------------------------------------------------------------------------*/

OnTopic/Repositories/TopicRepositoryBase.cs

@@ -355,13 +355,21 @@ public virtual int Save([ValidatedNotNull]Topic topic, bool isRecursive = false,
       /*------------------------------------------------------------------------------------------------------------------------
       | If new content type, add to cache
       \-----------------------------------------------------------------------------------------------------------------------*/
+      var asContentType         = topic as ContentTypeDescriptor;
       if (
         topic.IsNew &&
-        topic is ContentTypeDescriptor descriptor &&
+        asContentType != null &&
         _contentTypeDescriptors != null &&
         !_contentTypeDescriptors.Contains(topic.Key)
       ) {
-        _contentTypeDescriptors.Add(descriptor);
+        _contentTypeDescriptors.Add(asContentType);
+      }
+
+      /*------------------------------------------------------------------------------------------------------------------------
+      | If content type, and relationships have been updated, refresh permitted content types
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      if (asContentType != null && asContentType.Relationships.IsDirty()) {
+        asContentType.ResetPermittedContentTypes();
       }
 
       /*------------------------------------------------------------------------------------------------------------------------