Update ToChatResponse{Async} to also factor in AuthorName

src/Libraries/Microsoft.Extensions.AI.Abstractions/ChatCompletion/ChatResponseExtensions.cs

@@ -306,26 +306,19 @@ private static void FinalizeResponse(ChatResponse response)
     private static void ProcessUpdate(ChatResponseUpdate update, ChatResponse response)
     {
         // If there is no message created yet, or if the last update we saw had a different
-        // message ID or role than the newest update, create a new message.
-        ChatMessage message;
-        var isNewMessage = false;
-        if (response.Messages.Count == 0)
-        {
-            isNewMessage = true;
-        }
-        else if (update.MessageId is { Length: > 0 } updateMessageId
-            && response.Messages[response.Messages.Count - 1].MessageId is string lastMessageId
-            && updateMessageId != lastMessageId)
-        {
-            isNewMessage = true;
-        }
-        else if (update.Role is { } updateRole
-            && response.Messages[response.Messages.Count - 1].Role is { } lastRole
-            && updateRole != lastRole)
+        // identifying parts, create a new message.
+        bool isNewMessage = true;
+        if (response.Messages.Count != 0)
         {
-            isNewMessage = true;
+            var lastMessage = response.Messages[response.Messages.Count - 1];
+            isNewMessage =
+                NotEmptyOrEqual(update.AuthorName, lastMessage.AuthorName) ||
+                NotEmptyOrEqual(update.MessageId, lastMessage.MessageId) ||
+                NotNullOrEqual(update.Role, lastMessage.Role);
         }
 
+        // Get the message to target, either a new one or the last ones.
+        ChatMessage message;
         if (isNewMessage)
         {
             message = new(ChatRole.Assistant, []);
@@ -418,4 +411,12 @@ private static void ProcessUpdate(ChatResponseUpdate update, ChatResponse respon
             }
         }
     }
+
+    /// <summary>Gets whether both strings are not null/empty and not the same as each other.</summary>
+    private static bool NotEmptyOrEqual(string? s1, string? s2) =>
+        s1 is { Length: > 0 } str1 && s2 is { Length: > 0 } str2 && str1 != str2;
+
+    /// <summary>Gets whether two roles are not null and not the same as each other.</summary>
+    private static bool NotNullOrEqual(ChatRole? r1, ChatRole? r2) =>
+        r1.HasValue && r2.HasValue && r1.Value != r2.Value;
 }