[C#] Update module bindings to use new View ABI

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

@@ -1162,8 +1162,11 @@ public byte[] Invoke(
                 PublicTable.BSATN
             >.GetListSerializer();
             var listValue = ModuleRegistration.ToListOrEmpty(returnValue);
+            var header = new global::SpacetimeDB.Internal.ViewResultHeader.RowData(default);
+            var headerRW = new global::SpacetimeDB.Internal.ViewResultHeader.BSATN();
             using var output = new System.IO.MemoryStream();
             using var writer = new System.IO.BinaryWriter(output);
+            headerRW.Write(writer, header);
             listSerializer.Write(writer, listValue);
             return output.ToArray();
         }
@@ -1208,8 +1211,11 @@ public byte[] Invoke(
                 PublicTable.BSATN
             >.GetListSerializer();
             var listValue = ModuleRegistration.ToListOrEmpty(returnValue);
+            var header = new global::SpacetimeDB.Internal.ViewResultHeader.RowData(default);
+            var headerRW = new global::SpacetimeDB.Internal.ViewResultHeader.BSATN();
             using var output = new System.IO.MemoryStream();
             using var writer = new System.IO.BinaryWriter(output);
+            headerRW.Write(writer, header);
             listSerializer.Write(writer, listValue);
             return output.ToArray();
         }

crates/bindings-csharp/Codegen/Module.cs

@@ -1039,15 +1039,21 @@ public string GenerateDispatcherClass(uint index)
             ? $$$"""
                     var listSerializer = {{{ReturnType.BSATNName}}}.GetListSerializer();
                     var listValue = ModuleRegistration.ToListOrEmpty(returnValue);
+                    var header = new global::SpacetimeDB.Internal.ViewResultHeader.RowData(default);
+                    var headerRW = new global::SpacetimeDB.Internal.ViewResultHeader.BSATN();
                     using var output = new System.IO.MemoryStream();
                     using var writer = new System.IO.BinaryWriter(output);
+                    headerRW.Write(writer, header);
                     listSerializer.Write(writer, listValue);
                     return output.ToArray();
                 """
             : $$$"""
                     {{{ReturnType.BSATNName}}} returnRW = new();
+                    var header = new global::SpacetimeDB.Internal.ViewResultHeader.RowData(default);
+                    var headerRW = new global::SpacetimeDB.Internal.ViewResultHeader.BSATN();
                     using var output = new System.IO.MemoryStream();
                     using var writer = new System.IO.BinaryWriter(output);
+                    headerRW.Write(writer, header);
                     returnRW.Write(writer, returnValue);
                     return output.ToArray();            
                 """;

crates/bindings-csharp/Runtime/Internal/Module.cs

@@ -313,7 +313,7 @@
         catch (Exception e)
         {
             var error_str = e.Message ?? e.GetType().FullName;
             var error_bytes = System.Text.Encoding.UTF8.GetBytes(error_str);
             error.Write(error_bytes);
             return Errno.HOST_CALL_FAILURE;
         }
@@ -366,6 +366,30 @@
         }
     }
 
+    /// <summary>
+    /// Called by the host to execute a view when the sender calls the view identified by <paramref name="id" />.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The sender identity is passed as 4 <see cref="ulong" /> values (<paramref name="sender_0" /> through
+    /// <paramref name="sender_3" />) representing a little-endian <see cref="SpacetimeDB.Identity" />.
+    /// </para>
+    /// <para>
+    /// <paramref name="args" /> is a host-registered <see cref="BytesSource" /> containing the BSATN-encoded
+    /// view arguments. For empty arguments, <paramref name="args" /> will be invalid.
+    /// </para>
+    /// <para>
+    /// The view output is written to <paramref name="rows" />, a host-registered <see cref="BytesSink" />.
+    /// </para>
+    /// <para>
+    /// Note: a previous view ABI wrote the return rows directly to the sink.
+    /// The current ABI writes a BSATN-encoded <see cref="ViewResultHeader" /> first, in order to distinguish
+    /// between views that return row data and views that return queries.
+    /// </para>
+    /// <para>
+    /// The current ABI is identified by returning error code <c>2</c>.
+    /// </para>
+    /// </remarks>
     public static Errno __call_view__(
         uint id,
         ulong sender_0,
@@ -386,7 +410,7 @@
             using var reader = new BinaryReader(stream);
             var bytes = viewDispatchers[(int)id].Invoke(reader, ctx);
             rows.Write(bytes);
-            return Errno.OK;
+            return (Errno)2;
         }
         catch (Exception e)
         {
@@ -395,6 +419,26 @@
         }
     }
 
+    /// <summary>
+    /// Called by the host to execute an anonymous view.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// <paramref name="args" /> is a host-registered <see cref="BytesSource" /> containing the BSATN-encoded
+    /// view arguments. For empty arguments, <paramref name="args" /> will be invalid.
+    /// </para>
+    /// <para>
+    /// The view output is written to <paramref name="rows" />, a host-registered <see cref="BytesSink" />.
+    /// </para>
+    /// <para>
+    /// Note: a previous view ABI wrote the return rows directly to the sink.
+    /// The current ABI writes a BSATN-encoded <see cref="ViewResultHeader" /> first, in order to distinguish
+    /// between views that return row data and views that return queries.
+    /// </para>
+    /// <para>
+    /// The current ABI is identified by returning error code <c>2</c>.
+    /// </para>
+    /// </remarks>
     public static Errno __call_view_anon__(uint id, BytesSource args, BytesSink rows)
     {
         try
@@ -404,7 +448,7 @@
             using var reader = new BinaryReader(stream);
             var bytes = anonymousViewDispatchers[(int)id].Invoke(reader, ctx);
             rows.Write(bytes);
-            return Errno.OK;
+            return (Errno)2;
         }
         catch (Exception e)
         {

crates/bindings-csharp/Runtime/Internal/ViewResultHeader.cs

@@ -0,0 +1,5 @@
+namespace SpacetimeDB.Internal;
+
+[SpacetimeDB.Type]
+public partial record ViewResultHeader
+    : SpacetimeDB.TaggedEnum<(SpacetimeDB.Unit RowData, string RawSql)>;