.NET: bug fix for duplicate output on GitHubCopilotAgent (#3981)

* bug fix for duplicate output on GitHubCopilotAgent

* Add Test code for bug fix of duplicate output on GitHubCopilotAgenttT

* update Test code for bug fix of duplicate output on GitHubCopilotAgenttT

* update Test for duplicate output of GitHubCopilotAgent

---------

Co-authored-by: Mark Wallace <127216156+markwallace-microsoft@users.noreply.github.com>
Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>

Author: 3 people

dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/GitHubCopilotAgent.cs

@@ -346,14 +346,14 @@ private AgentResponseUpdate ConvertToAgentResponseUpdate(AssistantMessageDeltaEv
         };
     }
 
-    private AgentResponseUpdate ConvertToAgentResponseUpdate(AssistantMessageEvent assistantMessage)
+    internal AgentResponseUpdate ConvertToAgentResponseUpdate(AssistantMessageEvent assistantMessage)
     {
-        TextContent textContent = new(assistantMessage.Data?.Content ?? string.Empty)
+        AIContent content = new()
         {
             RawRepresentation = assistantMessage
         };
 
-        return new AgentResponseUpdate(ChatRole.Assistant, [textContent])
+        return new AgentResponseUpdate(ChatRole.Assistant, [content])
         {
             AgentId = this.Id,
             ResponseId = assistantMessage.Data?.MessageId,

dotnet/tests/Microsoft.Agents.AI.GitHub.Copilot.UnitTests/GitHubCopilotAgentTests.cs

@@ -221,4 +221,26 @@ public void CopyResumeSessionConfig_WithNullSource_ReturnsDefaults()
         Assert.Null(result.ConfigDir);
         Assert.True(result.Streaming);
     }
+
+    [Fact]
+    public void ConvertToAgentResponseUpdate_AssistantMessageEvent_DoesNotEmitTextContent()
+    {
+        var assistantMessage = new AssistantMessageEvent
+        {
+            Data = new AssistantMessageData
+            {
+                MessageId = "msg-456",
+                Content = "Some streamed content that was already delivered via delta events"
+            }
+        };
+        CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
+        const string TestId = "agent-id";
+        var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, id: TestId, tools: null);
+        AgentResponseUpdate result = agent.ConvertToAgentResponseUpdate(assistantMessage);
+
+        // result.Text need to be empty because the content was already delivered via delta events, and we want to avoid emitting duplicate content in the response update.
+        // The content should be delivered through TextContent in the Contents collection instead.
+        Assert.Empty(result.Text);
+        Assert.DoesNotContain(result.Contents, c => c is TextContent);
+    }
 }