Merge branch 'improvement/TopicRepository-IsNew-checks' into develop

Improved the `TopicRepository` base class to be more aware of `IsNew` conditions. In the case of loading a version of a new topic (8aacc5a) or saving a topic whose parent is new (4da0d43), an exception is thrown, as this is a completely unexpected scenario with no option for succeeding. The latter is validated via a unit test (854299a). In the case of `Move()` and `Delete()`, we instead just bypass their underlying `MoveTopic()` (bf1c584) and `DeleteTopic()` (7b46514) methods, which concrete implementations are responsible for implementing, thus allowing the basic validation and in-memory logic to be performed. This allows e.g. an `IsNew` topic to be deleted in memory, even though it obviously can't be deleted from the database. This satisfies the conditions of Issue #77.

Author: JeremyCaney

OnTopic.Tests/TopicRepositoryBaseTest.cs

@@ -910,9 +910,9 @@ public void Move_ContentTypeDescriptor_UpdatesContentTypeCache() {
     [Fact]
     public void Save_AttributeDescriptor_UpdatesContentType() {
 
-      var contentType           = new ContentTypeDescriptor("Parent", "ContentTypeDescriptor");
-      var attributeList         = new Topic("Attributes", "List", contentType);
-      var childContentType      = new ContentTypeDescriptor("Child", "ContentTypeDescriptor", contentType);
+      var contentType           = new ContentTypeDescriptor("Parent", "ContentTypeDescriptor", null, 1);
+      var attributeList         = new Topic("Attributes", "List", contentType, 2);
+      var childContentType      = new ContentTypeDescriptor("Child", "ContentTypeDescriptor", contentType, 3);
 
       Contract.Assume(childContentType);
 
@@ -924,7 +924,7 @@ public void Save_AttributeDescriptor_UpdatesContentType() {
 
       _topicRepository.Save(newAttribute);
 
-      Assert.True(childContentType.AttributeDescriptors.Count > attributeCount);
+      Assert.Equal<int>(attributeCount+1, childContentType.AttributeDescriptors.Count);
 
     }
 

OnTopic/Repositories/TopicRepository.cs

@@ -223,6 +223,11 @@ protected ContentTypeDescriptorCollection SetContentTypeDescriptors(ContentTypeD
     /// <inheritdoc />
     public override Topic? Load(Topic topic, DateTime version) {
       Contract.Requires(topic, nameof(topic));
+      Contract.Requires<ArgumentException>(
+        !topic.IsNew,
+        $"The version '{version}' of '{topic.GetUniqueKey()}' cannot be loaded. Topics must be saved in order to load " +
+        $"previous versions."
+      );
       return Load(topic.Id, version, topic);
     }
 
@@ -260,6 +265,15 @@ public override void Rollback([ValidatedNotNull]Topic topic, DateTime version) {
     /// <inheritdoc />
     public override sealed void Save([ValidatedNotNull] Topic topic, bool isRecursive = false) {
 
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Establish parameters
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      Contract.Requires(topic, nameof(topic));
+      Contract.Requires<ArgumentException>(
+        topic.Parent is null || !topic.Parent.IsNew,
+        $"The parent of '{topic.GetUniqueKey()}' is not saved. Topics can only be saved once their parent is saved."
+      );
+
       /*------------------------------------------------------------------------------------------------------------------------
       | Establish dependencies
       \-----------------------------------------------------------------------------------------------------------------------*/
@@ -501,7 +515,9 @@ topic.Parent is not null &&
       /*------------------------------------------------------------------------------------------------------------------------
       | Execute core implementation
       \-----------------------------------------------------------------------------------------------------------------------*/
-      MoveTopic(topic, target, sibling);
+      if (!topic.IsNew && !target.IsNew && !sibling.IsNew) {
+        MoveTopic(topic, target, sibling);
+      }
 
       /*------------------------------------------------------------------------------------------------------------------------
       | Perform base logic
@@ -595,7 +611,9 @@ public override sealed void Delete([ValidatedNotNull]Topic topic, bool isRecursi
       /*------------------------------------------------------------------------------------------------------------------------
       | Execute core implementation
       \-----------------------------------------------------------------------------------------------------------------------*/
-      DeleteTopic(topic);
+      if (!topic.IsNew) {
+        DeleteTopic(topic);
+      }
 
       /*------------------------------------------------------------------------------------------------------------------------
       | Remove from parent