Enable RefOption returns from Views to support Views returning a single class

crates/bindings-csharp/BSATN.Runtime/BSATN/Runtime.cs

@@ -203,6 +203,12 @@ public void Write(BinaryWriter writer, Inner? value)
 
     public AlgebraicType GetAlgebraicType(ITypeRegistrar registrar) =>
         AlgebraicType.MakeOption(innerRW.GetAlgebraicType(registrar));
+
+    // Return a List BSATN serializer that can serialize this option as an array
+    public static List<Inner, InnerRW> GetListSerializer()
+    {
+        return new List<Inner, InnerRW>();
+    }
 }
 
 // This implementation is nearly identical to RefOption. The only difference is the constraint on T.

crates/bindings-csharp/Codegen.Tests/fixtures/server/snapshots/Module#FFI.verified.cs

@@ -1,4 +1,4 @@
-//HintName: FFI.cs
+//HintName: FFI.cs
 // <auto-generated />
 #nullable enable
 // The runtime already defines SpacetimeDB.Internal.LocalReadOnly in Runtime\Internal\Module.cs as an empty partial type.
@@ -1699,6 +1699,9 @@ public void Invoke(BinaryReader reader, SpacetimeDB.Internal.IReducerContext ctx
     public static List<T> ToListOrEmpty<T>(T? value)
         where T : struct => value is null ? new List<T>() : new List<T> { value.Value };
 
+    public static List<T> ToListOrEmpty<T>(T? value)
+        where T : class => value is null ? new List<T>() : new List<T> { value };
+
 #if EXPERIMENTAL_WASM_AOT
     // In AOT mode we're building a library.
     // Main method won't be called automatically, so we need to export it as a preinit function.

crates/bindings-csharp/Codegen/Module.cs

@@ -978,6 +978,7 @@ public ViewDeclaration(GeneratorAttributeSyntaxContext context, DiagReporter dia
         // Validate return type: must be Option<T> or Vec<T>
         if (
             !ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.ValueOption")
+            && !ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.RefOption")
             && !ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.List")
         )
         {
@@ -1030,8 +1031,10 @@ public string GenerateDispatcherClass(uint index)
             ? "SpacetimeDB.AnonymousViewContext"
             : "SpacetimeDB.ViewContext";
 
-        var isValueOption = ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.ValueOption");
-        var writeOutput = isValueOption
+        var isOption =
+            ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.ValueOption")
+            || ReturnType.BSATNName.Contains("SpacetimeDB.BSATN.RefOption");
+        var writeOutput = isOption
             ? $$$"""
                     var listSerializer = {{{ReturnType.BSATNName}}}.GetListSerializer();
                     var listValue = ModuleRegistration.ToListOrEmpty(returnValue);
@@ -1934,6 +1937,9 @@ static class ModuleRegistration {
                         public static List<T> ToListOrEmpty<T>(T? value) where T : struct
                                 => value is null ? new List<T>() : new List<T> { value.Value };
 
+                        public static List<T> ToListOrEmpty<T>(T? value) where T : class
+                                => value is null ? new List<T>() : new List<T> { value };
+
                     #if EXPERIMENTAL_WASM_AOT
                         // In AOT mode we're building a library.
                         // Main method won't be called automatically, so we need to export it as a preinit function.

sdks/csharp/examples~/regression-tests/client/Program.cs

@@ -63,6 +63,8 @@ void OnConnected(DbConnection conn, Identity identity, string authToken)
         .Subscribe([
             "SELECT * FROM example_data",
             "SELECT * FROM my_player",
+            "SELECT * FROM my_account",
+            "SELECT * FROM my_account_missing",
             "SELECT * FROM players_at_level_one",
             "SELECT * FROM my_table",
             "SELECT * FROM null_string_nonnullable",
@@ -296,11 +298,21 @@ void OnSubscriptionApplied(SubscriptionEventContext context)
     // Views test
     Log.Debug("Checking Views are populated");
     Debug.Assert(context.Db.MyPlayer != null, "context.Db.MyPlayer != null");
+    Debug.Assert(context.Db.MyAccount != null, "context.Db.MyAccount != null");
+    Debug.Assert(context.Db.MyAccountMissing != null, "context.Db.MyAccountMissing != null");
     Debug.Assert(context.Db.PlayersAtLevelOne != null, "context.Db.PlayersAtLevelOne != null");
     Debug.Assert(
         context.Db.MyPlayer.Count > 0,
         $"context.Db.MyPlayer.Count = {context.Db.MyPlayer.Count}"
     );
+    Debug.Assert(
+        context.Db.MyAccount.Count == 1,
+        $"context.Db.MyAccount.Count = {context.Db.MyAccount.Count}"
+    );
+    Debug.Assert(
+        context.Db.MyAccountMissing.Count == 0,
+        $"context.Db.MyAccountMissing.Count = {context.Db.MyAccountMissing.Count}"
+    );
     Debug.Assert(
         context.Db.PlayersAtLevelOne.Count > 0,
         $"context.Db.PlayersAtLevelOne.Count = {context.Db.PlayersAtLevelOne.Count}"

sdks/csharp/examples~/regression-tests/server/Lib.cs

@@ -73,6 +73,19 @@ public partial struct Player
         public string Name;
     }
 
+    [SpacetimeDB.Table(Name = "account", Public = true)]
+    public partial class Account
+    {
+        [SpacetimeDB.PrimaryKey]
+        [SpacetimeDB.AutoInc]
+        public ulong Id;
+
+        [SpacetimeDB.Unique]
+        public Identity Identity;
+
+        public string Name = "";
+    }
+
     [SpacetimeDB.Table(Name = "player_level", Public = true)]
     public partial struct PlayerLevel
     {
@@ -137,7 +150,19 @@ public partial struct NullStringNullable
     [SpacetimeDB.View(Name = "my_player", Public = true)]
     public static Player? MyPlayer(ViewContext ctx)
     {
-        return ctx.Db.player.Identity.Find(ctx.Sender) as Player?;
+        return ctx.Db.player.Identity.Find(ctx.Sender);
+    }
+
+    [SpacetimeDB.View(Name = "my_account", Public = true)]
+    public static Account? MyAccount(ViewContext ctx)
+    {
+        return ctx.Db.account.Identity.Find(ctx.Sender) as Account;
+    }
+
+    [SpacetimeDB.View(Name = "my_account_missing", Public = true)]
+    public static Account? MyAccountMissing(ViewContext ctx)
+    {
+        return null;
     }
 
     // Multiple rows: return a list
@@ -269,6 +294,11 @@ public static void ClientConnected(ReducerContext ctx)
             ctx.Db.player_level.Insert(new PlayerLevel { PlayerId = playerId, Level = 1 });
         }
 
+        if (ctx.Db.account.Identity.Find(ctx.Sender) is null)
+        {
+            ctx.Db.account.Insert(new Account { Identity = ctx.Sender, Name = "Account" });
+        }
+
         if (ctx.Db.nullable_vec.Id.Find(1) is null)
         {
             ctx.Db.nullable_vec.Insert(new NullableVec