Tweak ChatMessage/StreamingChatCompletionUpdate.ToString (#5617)

* Tweak ChatMessage/StreamingChatCompletionUpdate.ToString

Include all text rather than just the first text content.

* Address PR feedback and fix / add tests

Author: stephentoub

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Text;
 using System.Text.Json.Serialization;
 using Microsoft.Shared.Diagnostics;
 
@@ -85,8 +86,26 @@ public ChatMessage Message
     public AdditionalPropertiesDictionary? AdditionalProperties { get; set; }
 
     /// <inheritdoc />
-    public override string ToString() =>
-        Choices is { Count: > 0 } choices ? string.Join(Environment.NewLine, choices) : string.Empty;
+    public override string ToString()
+    {
+        if (Choices.Count == 1)
+        {
+            return Choices[0].ToString();
+        }
+
+        StringBuilder sb = new();
+        for (int i = 0; i < Choices.Count; i++)
+        {
+            if (i > 0)
+            {
+                _ = sb.AppendLine().AppendLine();
+            }
+
+            _ = sb.Append("Choice ").Append(i).AppendLine(":").Append(Choices[i]);
+        }
+
+        return sb.ToString();
+    }
 
     /// <summary>Creates an array of <see cref="StreamingChatCompletionUpdate" /> instances that represent this <see cref="ChatCompletion" />.</summary>
     /// <returns>An array of <see cref="StreamingChatCompletionUpdate" /> instances that may be used to represent this <see cref="ChatCompletion" />.</returns>

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

@@ -95,5 +95,6 @@ public IList<AIContent> Contents
     public AdditionalPropertiesDictionary? AdditionalProperties { get; set; }
 
     /// <inheritdoc/>
-    public override string ToString() => Text ?? string.Empty;
+    public override string ToString() =>
+        string.Concat(Contents.OfType<TextContent>());
 }

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

@@ -116,5 +116,6 @@ public IList<AIContent> Contents
     public string? ModelId { get; set; }
 
     /// <inheritdoc/>
-    public override string ToString() => Text ?? string.Empty;
+    public override string ToString() =>
+        string.Concat(Contents.OfType<TextContent>());
 }

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatCompletionTests.cs

@@ -168,6 +168,40 @@ public void JsonSerialization_Roundtrips()
         Assert.Equal("value", ((JsonElement)value!).GetString());
     }
 
+    [Fact]
+    public void ToString_OneChoice_OutputsChatMessageToString()
+    {
+        ChatCompletion completion = new(
+        [
+            new ChatMessage(ChatRole.Assistant, "This is a test." + Environment.NewLine + "It's multiple lines.")
+        ]);
+
+        Assert.Equal(completion.Choices[0].Text, completion.ToString());
+    }
+
+    [Fact]
+    public void ToString_MultipleChoices_OutputsAllChoicesWithPrefix()
+    {
+        ChatCompletion completion = new(
+        [
+            new ChatMessage(ChatRole.Assistant, "This is a test." + Environment.NewLine + "It's multiple lines."),
+            new ChatMessage(ChatRole.Assistant, "So is" + Environment.NewLine + " this."),
+            new ChatMessage(ChatRole.Assistant, "And this."),
+        ]);
+
+        Assert.Equal(
+            "Choice 0:" + Environment.NewLine +
+            completion.Choices[0] + Environment.NewLine + Environment.NewLine +
+
+            "Choice 1:" + Environment.NewLine +
+            completion.Choices[1] + Environment.NewLine + Environment.NewLine +
+
+            "Choice 2:" + Environment.NewLine +
+            completion.Choices[2],
+
+            completion.ToString());
+    }
+
     [Fact]
     public void ToStreamingChatCompletionUpdates_SingleChoice()
     {

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatMessageTests.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text.Json;
 using Xunit;
 
@@ -91,7 +92,7 @@ public void Constructor_RoleList_PropsRoundtrip(int messageCount)
             }
 
             Assert.Equal("text-0", message.Text);
-            Assert.Equal("text-0", message.ToString());
+            Assert.Equal(string.Concat(Enumerable.Range(0, messageCount).Select(i => $"text-{i}")), message.ToString());
         }
 
         Assert.Null(message.AuthorName);
@@ -134,13 +135,13 @@ public void Text_GetSet_UsesFirstTextContent()
         TextContent textContent = Assert.IsType<TextContent>(message.Contents[3]);
         Assert.Equal("text-1", textContent.Text);
         Assert.Equal("text-1", message.Text);
-        Assert.Equal("text-1", message.ToString());
+        Assert.Equal("text-1text-2", message.ToString());
 
         message.Text = "text-3";
         Assert.Equal("text-3", message.Text);
         Assert.Equal("text-3", message.Text);
         Assert.Same(textContent, message.Contents[3]);
-        Assert.Equal("text-3", message.ToString());
+        Assert.Equal("text-3text-2", message.ToString());
     }
 
     [Fact]

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/StreamingChatCompletionUpdateTests.cs

@@ -103,13 +103,13 @@ public void Text_GetSet_UsesFirstTextContent()
         TextContent textContent = Assert.IsType<TextContent>(update.Contents[3]);
         Assert.Equal("text-1", textContent.Text);
         Assert.Equal("text-1", update.Text);
-        Assert.Equal("text-1", update.ToString());
+        Assert.Equal("text-1text-2", update.ToString());
 
         update.Text = "text-3";
         Assert.Equal("text-3", update.Text);
         Assert.Equal("text-3", update.Text);
         Assert.Same(textContent, update.Contents[3]);
-        Assert.Equal("text-3", update.ToString());
+        Assert.Equal("text-3text-2", update.ToString());
     }
 
     [Fact]