What causes "Result failed without an error object." in clockworklabs/SpacetimeDB?

Find the code constructing the Err value and guarantee a non-null error: Result .Err(error ?? fallbackError)

clockworklabs/SpacetimeDB · error · InvalidOperationException

Result failed without an error object.

Error message

Result failed without an error object.

What it means

Result<T,E>.UnwrapOrThrow expects the Err variant to carry a non-null error object; when it finds ErrR(null) there is nothing to surface, so it throws InvalidOperationException. This guards against silently reporting an empty failure and usually points at a producer that constructed Result.Err(null) - typically a null message, exception, or nullable reference-typed error.

Source

Thrown at crates/bindings-csharp/BSATN.Runtime/Builtins.cs:659

    public TResult Match<TResult>(Func<T, TResult> onOk, Func<E, TResult> onErr) =>
        this switch
        {
            OkR(var v) => onOk(v),
            ErrR(var e) => onErr(e),
            _ => throw new InvalidOperationException("Unknown Result variant."),
        };

    public static Result<T, E> Ok(T value) => new OkR(value);

    public static Result<T, E> Err(E error) => new ErrR(error);

    public T UnwrapOrThrow()
    {
        return this switch
        {
            OkR(var v) => v,
            ErrR(var e) when e is not null => throw new Exception(e.ToString()),
            ErrR(_) => throw new InvalidOperationException(
                "Result failed without an error object."
            ),
            _ => throw new InvalidOperationException("Unknown Result variant."),
        };
    }

    public T UnwrapOr(T defaultValue) =>
        this switch
        {
            OkR(var v) => v,
            _ => defaultValue,
        };

    public T UnwrapOrElse(Func<E, T> f) =>
        this switch
        {
            OkR(var v) => v,
            ErrR(var e) => f(e),

View on GitHub (pinned to 524b4487d9)

Solutions

Find the code constructing the Err value and guarantee a non-null error: Result<T,E>.Err(error ?? fallbackError)
Check the variant with Match/UnwrapOr before unwrapping instead of calling UnwrapOrThrow blind
If E is a string, use the exception's full ToString() or a constant message rather than ex.Message alone
Enable nullable reference types so Err(null) is a compile warning at the producer

Example fix

// before
return Result<string, string>.Err(ex.Message); // ex.Message may be null
...
var v = result.UnwrapOrThrow(); // throws 'Result failed without an error object.'

// after
return Result<string, string>.Err(ex.ToString());
...
var v = result.UnwrapOrThrow();

Defensive patterns

Strategy: validation

Validate before calling

// Inspect before unwrapping; never let a null error reach UnwrapOrThrow.
var payload = result.Match(
    onOk: v => (Value: v, Error: (string?)null),
    onErr: e => (Value: default(T), Error: e?.ToString() ?? "unknown error"));
if (payload.Error is null) { /* use payload.Value */ }

Try / catch

try { value = result.UnwrapOrThrow(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("without an error object"))
{ /* producer bug: Err was constructed with null; log and fail loudly */ }

Prevention

Never construct Result<T,E>.Err(null) - coalesce to a fallback error first
Enable nullable reference types so null errors warn at the construction site
Prefer Match/UnwrapOr over UnwrapOrThrow when the producer is not fully under your control

When it happens

Trigger: Result<T,string>.Err(null!); building Err from ex.Message where the exception has no message; an API contract where E is a nullable/optional error type and callers pass default; default(Result<T,E>) misuse.

Common situations: Wrapping third-party exceptions with empty messages into Result errors; FFI boundaries returning null error payloads; generics where E is a reference type and null sneaks through unchecked nullable annotations.

Related errors

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/6ea70f3dfd9a382e. Report an issue: GitHub.