Add method to IStructuralReadWrite to get an IReadWrite<Self>. This is technically a breaking change if anyone is manually implementing IStructuralReadWrite.

Author: kazimuth

crates/bindings-csharp/BSATN.Codegen/Type.cs

@@ -512,6 +512,10 @@ public void WriteFields(System.IO.BinaryWriter writer) {
                 )}}
                 }
 
+                object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer() {
+                    return new BSATN();
+                }
+
             """
             );
 

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

@@ -2,12 +2,61 @@ namespace SpacetimeDB.BSATN;
 
 using System.Text;
 
+/// <summary>
+/// Implemented by product types marked with [SpacetimeDB.Type].
+/// All rows in SpacetimeDB are product types, so this is also implemented by all row types.
+///
+/// </summary>
 public interface IStructuralReadWrite
 {
+    /// <summary>
+    /// Initialize this value from the reader.
+    /// The reader is assumed to store a <see href="https://spacetimedb.com/docs/bsatn">BSATN-encoded</see>
+    /// value of this type.
+    /// Advances the reader to the first byte past the end of the read value.
+    /// Throws an exception if this would advance past the end of the reader.
+    /// </summary>
+    /// <param name="reader"></param>
     void ReadFields(BinaryReader reader);
 
+    /// <summary>
+    /// Write the fields of this type to the writer.
+    /// Throws an exception if the underlying writer throws.
+    /// Throws if this value is malformed (i.e. has null values for fields that
+    /// are not explicitly marked nullable.)
+    /// </summary>
+    /// <param name="writer"></param>
     void WriteFields(BinaryWriter writer);
 
+    /// <summary>
+    /// Get an IReadWrite implementation that can read values of this type.
+    /// In Rust, this would return <c>IReadWrite&lt;Self&gt;</c>, but the C# type system
+    /// has no equivalent Self type -- that is, you can't use the implementing type in type signatures
+    /// in an interface. So, you have to manually downcast.
+    /// A typical invocation looks like: <c>(IReadWrite&lt;Row&gt;) new Row().GetSerializer()</c>
+    ///
+    /// This is an instance method because of limitations of C# interfaces.
+    /// (C# 11 has static virtual interface members, but Unity does not support C# 11.)
+    /// This method always works, whether or not the row it is called on is correctly initialized.
+    /// The returned serializer has nothing to do with the row GetSerializer is called on -- it returns
+    /// new rows and does not modify or interact with the original row.
+    ///
+    /// Using the resulting serializer rather than <c>Read&lt;T&gt;</c> is usually faster in Mono/IL2CPP.
+    /// This is because we manually monomorphise the code to read rows in our automatically-generated
+    /// implementation of IReadWrite. This allows rows to be initialized with new() rather than reflection
+    /// in the generated code.
+    /// </summary>
+    /// <returns>An <c>IReadWrite&lt;T&gt;</c> for <c>T : IStructuralReadWrite</c>.</returns>
+    object GetSerializer();
+
+    /// <summary>
+    /// Read a row from the reader.
+    /// This method usually uses Activator.CreateInstance to create the resulting row;
+    /// if this is too slow, prefer using GetSerializer.
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    /// <param name="reader"></param>
+    /// <returns></returns>
     static T Read<T>(BinaryReader reader)
         where T : IStructuralReadWrite, new()
     {
@@ -38,12 +87,34 @@ public static byte[] ToBytes<T>(T value)
     }
 }
 
+/// <summary>
+/// Interface for types that know how to serialize another type.
+/// We auto-generate an implementation of <c>IReadWrite&lt;T&gt;</c> for all
+/// types marked with <c>[SpacetimeDB.Type]</c>. For a type <c>T</c>, this implementation
+/// is accessible at <c>T.BSATN</c>. The implementation is always a zero-sized struct.
+/// </summary>
+/// <typeparam name="T"></typeparam>
 public interface IReadWrite<T>
 {
+    /// <summary>
+    /// Read a BSATN-encoded value of type T from the reader.
+    /// Throws on end-of-stream or if the stream is malformed.
+    /// Advances the reader to the first byte past the end of the encoded value.
+    /// </summary>
+    /// <param name="reader"></param>
+    /// <returns></returns>
     T Read(BinaryReader reader);
 
+    /// <summary>
+    /// Write a BSATN-encoded value of type T to the writer.
+    /// </summary>
     void Write(BinaryWriter writer, T value);
 
+    /// <summary>
+    /// Get metadata for this type. Used in module initialization.
+    /// </summary>
+    /// <param name="registrar"></param>
+    /// <returns></returns>
     AlgebraicType GetAlgebraicType(ITypeRegistrar registrar);
 }
 

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

@@ -392,6 +392,11 @@ public readonly void WriteFields(BinaryWriter writer)
         BSATN.MicrosecondsSinceUnixEpoch.Write(writer, MicrosecondsSinceUnixEpoch);
     }
 
+    readonly object IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public readonly partial struct BSATN : IReadWrite<Timestamp>
     {
         internal static readonly I64 MicrosecondsSinceUnixEpoch = new();
@@ -463,6 +468,11 @@ public readonly void WriteFields(BinaryWriter writer)
         BSATN.__time_duration_micros__.Write(writer, Microseconds);
     }
 
+    readonly object IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public readonly partial struct BSATN : IReadWrite<TimeDuration>
     {
         internal static readonly I64 __time_duration_micros__ = new();

crates/bindings-csharp/Codegen.Tests/fixtures/client/snapshots/Type#CustomClass.verified.cs

@@ -16,6 +16,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.StringField.Write(writer, StringField);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"CustomClass {{ IntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntField)}, StringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringField)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/client/snapshots/Type#CustomStruct.verified.cs

@@ -18,6 +18,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.StringField.Write(writer, StringField);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"CustomStruct {{ IntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntField)}, StringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringField)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/client/snapshots/Type#PublicTable.verified.cs

@@ -62,6 +62,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.NullableReferenceField.Write(writer, NullableReferenceField);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"PublicTable {{ ByteField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ByteField)}, UshortField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UshortField)}, UintField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UintField)}, UlongField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UlongField)}, U128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(U128Field)}, U256Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(U256Field)}, SbyteField = {SpacetimeDB.BSATN.StringUtil.GenericToString(SbyteField)}, ShortField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ShortField)}, IntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntField)}, LongField = {SpacetimeDB.BSATN.StringUtil.GenericToString(LongField)}, I128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(I128Field)}, I256Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(I256Field)}, BoolField = {SpacetimeDB.BSATN.StringUtil.GenericToString(BoolField)}, FloatField = {SpacetimeDB.BSATN.StringUtil.GenericToString(FloatField)}, DoubleField = {SpacetimeDB.BSATN.StringUtil.GenericToString(DoubleField)}, StringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringField)}, IdentityField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IdentityField)}, ConnectionIdField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ConnectionIdField)}, CustomStructField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomStructField)}, CustomClassField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomClassField)}, CustomEnumField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomEnumField)}, CustomTaggedEnumField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomTaggedEnumField)}, ListField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ListField)}, NullableValueField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableValueField)}, NullableReferenceField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableReferenceField)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#InAnotherNamespace.TestDuplicateTableName.verified.cs

@@ -20,6 +20,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.Z.Write(writer, Z);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"BTreeMultiColumn {{ X = {SpacetimeDB.BSATN.StringUtil.GenericToString(X)}, Y = {SpacetimeDB.BSATN.StringUtil.GenericToString(Y)}, Z = {SpacetimeDB.BSATN.StringUtil.GenericToString(Z)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#TestAutoIncNotInteger.verified.cs

@@ -20,6 +20,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.Faction.Write(writer, Faction);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"BTreeViews {{ Id = {SpacetimeDB.BSATN.StringUtil.GenericToString(Id)}, X = {SpacetimeDB.BSATN.StringUtil.GenericToString(X)}, Y = {SpacetimeDB.BSATN.StringUtil.GenericToString(Y)}, Faction = {SpacetimeDB.BSATN.StringUtil.GenericToString(Faction)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#TestDuplicateTableName.verified.cs

@@ -20,6 +20,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.Bar.Write(writer, Bar);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"MultiTableRow {{ Name = {SpacetimeDB.BSATN.StringUtil.GenericToString(Name)}, Foo = {SpacetimeDB.BSATN.StringUtil.GenericToString(Foo)}, Bar = {SpacetimeDB.BSATN.StringUtil.GenericToString(Bar)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#TestIndexIssues.verified.cs

@@ -8,6 +8,11 @@ public void ReadFields(System.IO.BinaryReader reader) { }
 
     public void WriteFields(System.IO.BinaryWriter writer) { }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() => $"PrivateTable {{  }}";
 
     public readonly partial struct BSATN : SpacetimeDB.BSATN.IReadWrite<PrivateTable>

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#TestScheduleIssues.verified.cs

@@ -68,6 +68,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.NullableReferenceField.Write(writer, NullableReferenceField);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"PublicTable {{ Id = {SpacetimeDB.BSATN.StringUtil.GenericToString(Id)}, ByteField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ByteField)}, UshortField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UshortField)}, UintField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UintField)}, UlongField = {SpacetimeDB.BSATN.StringUtil.GenericToString(UlongField)}, UInt128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(UInt128Field)}, U128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(U128Field)}, U256Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(U256Field)}, SbyteField = {SpacetimeDB.BSATN.StringUtil.GenericToString(SbyteField)}, ShortField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ShortField)}, IntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntField)}, LongField = {SpacetimeDB.BSATN.StringUtil.GenericToString(LongField)}, Int128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(Int128Field)}, I128Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(I128Field)}, I256Field = {SpacetimeDB.BSATN.StringUtil.GenericToString(I256Field)}, BoolField = {SpacetimeDB.BSATN.StringUtil.GenericToString(BoolField)}, FloatField = {SpacetimeDB.BSATN.StringUtil.GenericToString(FloatField)}, DoubleField = {SpacetimeDB.BSATN.StringUtil.GenericToString(DoubleField)}, StringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringField)}, IdentityField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IdentityField)}, ConnectionIdField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ConnectionIdField)}, CustomStructField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomStructField)}, CustomClassField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomClassField)}, CustomEnumField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomEnumField)}, CustomTaggedEnumField = {SpacetimeDB.BSATN.StringUtil.GenericToString(CustomTaggedEnumField)}, ListField = {SpacetimeDB.BSATN.StringUtil.GenericToString(ListField)}, NullableValueField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableValueField)}, NullableReferenceField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableReferenceField)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module#TestUniqueNotEquatable.verified.cs

@@ -18,6 +18,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.Unique2.Write(writer, Unique2);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"RegressionMultipleUniqueIndexesHadSameName {{ Unique1 = {SpacetimeDB.BSATN.StringUtil.GenericToString(Unique1)}, Unique2 = {SpacetimeDB.BSATN.StringUtil.GenericToString(Unique2)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Type#TestTypeParams_T_.verified.cs

@@ -22,6 +22,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
             BSATN.Text.Write(writer, Text);
         }
 
+        object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+        {
+            return new BSATN();
+        }
+
         public override string ToString() =>
             $"SendMessageTimer {{ ScheduledId = {SpacetimeDB.BSATN.StringUtil.GenericToString(ScheduledId)}, ScheduledAt = {SpacetimeDB.BSATN.StringUtil.GenericToString(ScheduledAt)}, Text = {SpacetimeDB.BSATN.StringUtil.GenericToString(Text)} }}";
 

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Type#TestUnsupportedType.verified.cs

@@ -30,6 +30,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.StringListListArray.Write(writer, StringListListArray);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"ContainsNestedLists {{ IntList = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntList)}, StringList = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringList)}, IntArray = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntArray)}, StringArray = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringArray)}, IntArrayArrayList = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntArrayArrayList)}, IntListListArray = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntListListArray)}, StringArrayArrayList = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringArrayArrayList)}, StringListListArray = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringListListArray)} }}";
 

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

@@ -20,6 +20,11 @@ public void WriteFields(System.IO.BinaryWriter writer)
         BSATN.NullableStringField.Write(writer, NullableStringField);
     }
 
+    object SpacetimeDB.BSATN.IStructuralReadWrite.GetSerializer()
+    {
+        return new BSATN();
+    }
+
     public override string ToString() =>
         $"CustomClass {{ IntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(IntField)}, StringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(StringField)}, NullableIntField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableIntField)}, NullableStringField = {SpacetimeDB.BSATN.StringUtil.GenericToString(NullableStringField)} }}";