Fix codegen for discriminated unions nested within other types (#736)

* Fix C# codegen for discriminated unions nested within other types. Result is strongly-typed APIs for permission requests

* Fix permissions scenario to use strongly-typed PermissionRequest variants

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

dotnet/src/Generated/SessionEvents.cs

@@ -1528,7 +1528,7 @@ public partial class PermissionRequestedData
     public required string RequestId { get; set; }
 
     [JsonPropertyName("permissionRequest")]
-    public required object PermissionRequest { get; set; }
+    public required PermissionRequest PermissionRequest { get; set; }
 }
 
 public partial class PermissionCompletedData
@@ -2095,6 +2095,193 @@ public partial class SystemMessageDataMetadata
     public Dictionary<string, object>? Variables { get; set; }
 }
 
+public partial class PermissionRequestShellCommandsItem
+{
+    [JsonPropertyName("identifier")]
+    public required string Identifier { get; set; }
+
+    [JsonPropertyName("readOnly")]
+    public required bool ReadOnly { get; set; }
+}
+
+public partial class PermissionRequestShellPossibleUrlsItem
+{
+    [JsonPropertyName("url")]
+    public required string Url { get; set; }
+}
+
+public partial class PermissionRequestShell : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "shell";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("fullCommandText")]
+    public required string FullCommandText { get; set; }
+
+    [JsonPropertyName("intention")]
+    public required string Intention { get; set; }
+
+    [JsonPropertyName("commands")]
+    public required PermissionRequestShellCommandsItem[] Commands { get; set; }
+
+    [JsonPropertyName("possiblePaths")]
+    public required string[] PossiblePaths { get; set; }
+
+    [JsonPropertyName("possibleUrls")]
+    public required PermissionRequestShellPossibleUrlsItem[] PossibleUrls { get; set; }
+
+    [JsonPropertyName("hasWriteFileRedirection")]
+    public required bool HasWriteFileRedirection { get; set; }
+
+    [JsonPropertyName("canOfferSessionApproval")]
+    public required bool CanOfferSessionApproval { get; set; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("warning")]
+    public string? Warning { get; set; }
+}
+
+public partial class PermissionRequestWrite : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "write";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("intention")]
+    public required string Intention { get; set; }
+
+    [JsonPropertyName("fileName")]
+    public required string FileName { get; set; }
+
+    [JsonPropertyName("diff")]
+    public required string Diff { get; set; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("newFileContents")]
+    public string? NewFileContents { get; set; }
+}
+
+public partial class PermissionRequestRead : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "read";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("intention")]
+    public required string Intention { get; set; }
+
+    [JsonPropertyName("path")]
+    public required string Path { get; set; }
+}
+
+public partial class PermissionRequestMcp : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "mcp";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("serverName")]
+    public required string ServerName { get; set; }
+
+    [JsonPropertyName("toolName")]
+    public required string ToolName { get; set; }
+
+    [JsonPropertyName("toolTitle")]
+    public required string ToolTitle { get; set; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("args")]
+    public object? Args { get; set; }
+
+    [JsonPropertyName("readOnly")]
+    public required bool ReadOnly { get; set; }
+}
+
+public partial class PermissionRequestUrl : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "url";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("intention")]
+    public required string Intention { get; set; }
+
+    [JsonPropertyName("url")]
+    public required string Url { get; set; }
+}
+
+public partial class PermissionRequestMemory : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "memory";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("subject")]
+    public required string Subject { get; set; }
+
+    [JsonPropertyName("fact")]
+    public required string Fact { get; set; }
+
+    [JsonPropertyName("citations")]
+    public required string Citations { get; set; }
+}
+
+public partial class PermissionRequestCustomTool : PermissionRequest
+{
+    [JsonIgnore]
+    public override string Kind => "custom-tool";
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("toolCallId")]
+    public string? ToolCallId { get; set; }
+
+    [JsonPropertyName("toolName")]
+    public required string ToolName { get; set; }
+
+    [JsonPropertyName("toolDescription")]
+    public required string ToolDescription { get; set; }
+
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonPropertyName("args")]
+    public object? Args { get; set; }
+}
+
+[JsonPolymorphic(
+    TypeDiscriminatorPropertyName = "kind",
+    UnknownDerivedTypeHandling = JsonUnknownDerivedTypeHandling.FallBackToBaseType)]
+[JsonDerivedType(typeof(PermissionRequestShell), "shell")]
+[JsonDerivedType(typeof(PermissionRequestWrite), "write")]
+[JsonDerivedType(typeof(PermissionRequestRead), "read")]
+[JsonDerivedType(typeof(PermissionRequestMcp), "mcp")]
+[JsonDerivedType(typeof(PermissionRequestUrl), "url")]
+[JsonDerivedType(typeof(PermissionRequestMemory), "memory")]
+[JsonDerivedType(typeof(PermissionRequestCustomTool), "custom-tool")]
+public partial class PermissionRequest
+{
+    [JsonPropertyName("kind")]
+    public virtual string Kind { get; set; } = string.Empty;
+}
+
+
 public partial class PermissionCompletedDataResult
 {
     [JsonPropertyName("kind")]
@@ -2273,6 +2460,16 @@ public enum PermissionCompletedDataResultKind
 [JsonSerializable(typeof(PermissionCompletedData))]
 [JsonSerializable(typeof(PermissionCompletedDataResult))]
 [JsonSerializable(typeof(PermissionCompletedEvent))]
+[JsonSerializable(typeof(PermissionRequest))]
+[JsonSerializable(typeof(PermissionRequestCustomTool))]
+[JsonSerializable(typeof(PermissionRequestMcp))]
+[JsonSerializable(typeof(PermissionRequestMemory))]
+[JsonSerializable(typeof(PermissionRequestRead))]
+[JsonSerializable(typeof(PermissionRequestShell))]
+[JsonSerializable(typeof(PermissionRequestShellCommandsItem))]
+[JsonSerializable(typeof(PermissionRequestShellPossibleUrlsItem))]
+[JsonSerializable(typeof(PermissionRequestUrl))]
+[JsonSerializable(typeof(PermissionRequestWrite))]
 [JsonSerializable(typeof(PermissionRequestedData))]
 [JsonSerializable(typeof(PermissionRequestedEvent))]
 [JsonSerializable(typeof(SessionCompactionCompleteData))]

dotnet/src/Session.cs

@@ -339,7 +339,7 @@ internal async Task<PermissionRequestResult> HandlePermissionRequestAsync(JsonEl
             };
         }
 
-        var request = JsonSerializer.Deserialize(permissionRequestData.GetRawText(), SessionJsonContext.Default.PermissionRequest)
+        var request = JsonSerializer.Deserialize(permissionRequestData.GetRawText(), SessionEventsJsonContext.Default.PermissionRequest)
             ?? throw new InvalidOperationException("Failed to deserialize permission request");
 
         var invocation = new PermissionInvocation
@@ -457,27 +457,16 @@ private async Task ExecuteToolAndRespondAsync(string requestId, string toolName,
     /// <summary>
     /// Executes a permission handler and sends the result back via the HandlePendingPermissionRequest RPC.
     /// </summary>
-    private async Task ExecutePermissionAndRespondAsync(string requestId, object permissionRequestData, PermissionRequestHandler handler)
+    private async Task ExecutePermissionAndRespondAsync(string requestId, PermissionRequest permissionRequest, PermissionRequestHandler handler)
     {
         try
         {
-            // PermissionRequestedData.PermissionRequest is typed as `object` in generated code,
-            // but StreamJsonRpc deserializes it as a JsonElement.
-            if (permissionRequestData is not JsonElement permJsonElement)
-            {
-                throw new InvalidOperationException(
-                    $"Permission request data must be a {nameof(JsonElement)}; received {permissionRequestData.GetType().Name}");
-            }
-
-            var request = JsonSerializer.Deserialize(permJsonElement.GetRawText(), SessionJsonContext.Default.PermissionRequest)
-                ?? throw new InvalidOperationException("Failed to deserialize permission request");
-
             var invocation = new PermissionInvocation
             {
                 SessionId = SessionId
             };
 
-            var result = await handler(request, invocation);
+            var result = await handler(permissionRequest, invocation);
             await Rpc.Permissions.HandlePendingPermissionRequestAsync(requestId, result);
         }
         catch (Exception)
@@ -780,7 +769,6 @@ internal record SessionDestroyRequest
         DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull)]
     [JsonSerializable(typeof(GetMessagesRequest))]
     [JsonSerializable(typeof(GetMessagesResponse))]
-    [JsonSerializable(typeof(PermissionRequest))]
     [JsonSerializable(typeof(SendMessageRequest))]
     [JsonSerializable(typeof(SendMessageResponse))]
     [JsonSerializable(typeof(SessionAbortRequest))]

dotnet/src/Types.cs

@@ -266,38 +266,6 @@ public class ToolInvocation
 /// </summary>
 public delegate Task<object?> ToolHandler(ToolInvocation invocation);
 
-/// <summary>
-/// Represents a permission request from the server for a tool operation.
-/// </summary>
-public class PermissionRequest
-{
-    /// <summary>
-    /// Kind of permission being requested.
-    /// <list type="bullet">
-    /// <item><description><c>"shell"</c> — execute a shell command.</description></item>
-    /// <item><description><c>"write"</c> — write to a file.</description></item>
-    /// <item><description><c>"read"</c> — read a file.</description></item>
-    /// <item><description><c>"mcp"</c> — invoke an MCP server tool.</description></item>
-    /// <item><description><c>"url"</c> — access a URL.</description></item>
-    /// <item><description><c>"custom-tool"</c> — invoke a custom tool.</description></item>
-    /// </list>
-    /// </summary>
-    [JsonPropertyName("kind")]
-    public string Kind { get; set; } = string.Empty;
-
-    /// <summary>
-    /// Identifier of the tool call that triggered the permission request.
-    /// </summary>
-    [JsonPropertyName("toolCallId")]
-    public string? ToolCallId { get; set; }
-
-    /// <summary>
-    /// Additional properties not explicitly modeled.
-    /// </summary>
-    [JsonExtensionData]
-    public Dictionary<string, object>? ExtensionData { get; set; }
-}
-
 /// <summary>Describes the kind of a permission request result.</summary>
 [JsonConverter(typeof(PermissionRequestResultKind.Converter))]
 [DebuggerDisplay("{Value,nq}")]
@@ -2005,7 +1973,6 @@ public class SetForegroundSessionResponse
 [JsonSerializable(typeof(ModelPolicy))]
 [JsonSerializable(typeof(ModelSupports))]
 [JsonSerializable(typeof(ModelVisionLimits))]
-[JsonSerializable(typeof(PermissionRequest))]
 [JsonSerializable(typeof(PermissionRequestResult))]
 [JsonSerializable(typeof(PingRequest))]
 [JsonSerializable(typeof(PingResponse))]

dotnet/test/PermissionTests.cs

@@ -231,7 +231,7 @@ public async Task Should_Receive_ToolCallId_In_Permission_Requests()
         {
             OnPermissionRequest = (request, invocation) =>
             {
-                if (!string.IsNullOrEmpty(request.ToolCallId))
+                if (request is PermissionRequestShell shell && !string.IsNullOrEmpty(shell.ToolCallId))
                 {
                     receivedToolCallId = true;
                 }

dotnet/test/ToolsTests.cs

@@ -237,11 +237,9 @@ await session.SendAsync(new MessageOptions
         Assert.Contains("HELLO", assistantMessage!.Data.Content ?? string.Empty);
 
         // Should have received a custom-tool permission request with the correct tool name
-        var customToolRequest = permissionRequests.FirstOrDefault(r => r.Kind == "custom-tool");
+        var customToolRequest = permissionRequests.OfType<PermissionRequestCustomTool>().FirstOrDefault();
         Assert.NotNull(customToolRequest);
-        Assert.True(customToolRequest!.ExtensionData?.ContainsKey("toolName") ?? false);
-        var toolName = ((JsonElement)customToolRequest.ExtensionData!["toolName"]).GetString();
-        Assert.Equal("encrypt_string", toolName);
+        Assert.Equal("encrypt_string", customToolRequest!.ToolName);
 
         [Description("Encrypts a string")]
         static string EncryptStringForPermission([Description("String to encrypt")] string input)