clockworklabs/SpacetimeDB · error · ArgumentNullException

Cannot serialize a null string as BSATN String. To serialize

Error message

Cannot serialize a null string as BSATN String. To serialize a null string you must use a nullable string (string?) so it is encoded as a BSATN option.

What it means

Error "Cannot serialize a null string as BSATN String. To serialize a null string you must use a nullable string (string?) so it is encoded as a BSATN option." thrown in clockworklabs/SpacetimeDB.

Source

Thrown at crates/bindings-csharp/BSATN.Runtime/BSATN/Runtime.cs:560

        writer.Write(value.Length);
        writer.Write(value);
    }

    public AlgebraicType GetAlgebraicType(ITypeRegistrar registrar) =>
        new AlgebraicType.Array(new AlgebraicType.U8(default));
}

// String is a special case of byte array with extra checks.
public readonly struct String : IReadWrite<string>
{
    public string Read(BinaryReader reader) =>
        Encoding.UTF8.GetString(ByteArray.Instance.Read(reader));

    public void Write(BinaryWriter writer, string value)
    {
        if (value is null)
        {
            throw new ArgumentNullException(
                nameof(value),
                "Cannot serialize a null string as BSATN String. To serialize a null string you must use a nullable string (string?) so it is encoded as a BSATN option."
            );
        }

        ByteArray.Instance.Write(writer, Encoding.UTF8.GetBytes(value));
    }

    public AlgebraicType GetAlgebraicType(ITypeRegistrar registrar) =>
        new AlgebraicType.String(default);
}

public readonly struct List<Element, ElementRW> : IReadWrite<List<Element>>
    where ElementRW : IReadWrite<Element>, new()
{
    private static readonly Enumerable<Element, ElementRW> enumerable = new();
    private static readonly ElementRW elementRW = new();

View on GitHub (pinned to 524b4487d9)

When it happens

Trigger: Thrown at crates/bindings-csharp/BSATN.Runtime/BSATN/Runtime.cs:560 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/d1162b08a32c5bed. Report an issue: GitHub.