Add DebuggerDisplay to SessionEvent for better debugging

Added [DebuggerDisplay] attribute to SessionEvent base class to show JSON in debugger views.

Author: stephentoub

dotnet/src/Generated/SessionEvents.cs

@@ -8,6 +8,7 @@
 // Generated code does not have XML doc comments; suppress CS1591 to avoid warnings.
 #pragma warning disable CS1591
 
+using System.Diagnostics;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -16,6 +17,7 @@ namespace GitHub.Copilot.SDK;
 /// <summary>
 /// Base class for all session events with polymorphic JSON serialization.
 /// </summary>
+[DebuggerDisplay("{DebuggerDisplay,nq}")]
 [JsonPolymorphic(
     TypeDiscriminatorPropertyName = "type",
     UnknownDerivedTypeHandling = JsonUnknownDerivedTypeHandling.FailSerialization)]
@@ -104,6 +106,9 @@ public static SessionEvent FromJson(string json) =>
 
     public string ToJson() =>
         JsonSerializer.Serialize(this, SessionEventsJsonContext.Default.SessionEvent);
+
+    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+    private string DebuggerDisplay => ToJson();
 }
 
 /// <summary>

scripts/codegen/csharp.ts

@@ -428,6 +428,7 @@ function generateSessionEventsCode(schema: JSONSchema7): string {
 // Generated code does not have XML doc comments; suppress CS1591 to avoid warnings.
 #pragma warning disable CS1591
 
+using System.Diagnostics;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -438,6 +439,7 @@ namespace GitHub.Copilot.SDK;
     lines.push(`/// <summary>`);
     lines.push(`/// Base class for all session events with polymorphic JSON serialization.`);
     lines.push(`/// </summary>`);
+    lines.push(`[DebuggerDisplay("{DebuggerDisplay,nq}")]`);
     lines.push(`[JsonPolymorphic(`, `    TypeDiscriminatorPropertyName = "type",`, `    UnknownDerivedTypeHandling = JsonUnknownDerivedTypeHandling.FailSerialization)]`);
     for (const variant of [...variants].sort((a, b) => a.typeName.localeCompare(b.typeName))) {
         lines.push(`[JsonDerivedType(typeof(${variant.className}), "${variant.typeName}")]`);
@@ -449,7 +451,8 @@ namespace GitHub.Copilot.SDK;
     lines.push(`    /// <summary>`, `    /// The event type discriminator.`, `    /// </summary>`);
     lines.push(`    [JsonIgnore]`, `    public abstract string Type { get; }`, "");
     lines.push(`    public static SessionEvent FromJson(string json) =>`, `        JsonSerializer.Deserialize(json, SessionEventsJsonContext.Default.SessionEvent)!;`, "");
-    lines.push(`    public string ToJson() =>`, `        JsonSerializer.Serialize(this, SessionEventsJsonContext.Default.SessionEvent);`, `}`, "");
+    lines.push(`    public string ToJson() =>`, `        JsonSerializer.Serialize(this, SessionEventsJsonContext.Default.SessionEvent);`, "");
+    lines.push(`    [DebuggerBrowsable(DebuggerBrowsableState.Never)]`, `    private string DebuggerDisplay => ToJson();`, `}`, "");
 
     // Event classes with XML docs
     for (const variant of variants) {