microsoft/aspire · error · InvalidOperationException

The " " launch configuration producer for resource ' '…

Error message

The "{launchConfigurationType}" launch configuration producer for resource '{resourceName}' returned null. The producer owns the complete launch configuration, so it must always return one.

What it means

A launch configuration producer registered via debug support must always yield a non-null launch configuration because it fully owns constructing it. SupportsDebuggingAnnotation.Create wraps the producer and throws this InvalidOperationException if the awaited producer returns null. This catches buggy producers (e.g. a method with a nullable return that falls through to null) before an incomplete launch configuration is used.

Solutions

Fix the producer to always return a constructed launch configuration object (throw on unrecoverable paths instead of returning null)
Return an empty/default launch configuration rather than null for unknown launch modes
Log and inspect the producer's code paths that can return null

Example fix

// before
async Task<LaunchConfiguration> ProduceAsync(LaunchConfigurationCallbackContext ctx) =>
    ctx.LaunchMode == "Debug" ? new LaunchConfiguration() : null;
// after
async Task<LaunchConfiguration> ProduceAsync(LaunchConfigurationCallbackContext ctx) =>
    ctx.LaunchMode == "Debug"
        ? new LaunchConfiguration()
        : throw new InvalidOperationException($"Unsupported launch mode '{ctx.LaunchMode}'.");

Defensive patterns

Strategy: type-guard

Validate before calling

object EnsureNotNull(LaunchConfiguration? config) =>
    config ?? throw new InvalidOperationException("Producer returned null; return a LaunchConfiguration instance.");

Type guard

if (producerResult is null) throw new InvalidOperationException("Launch configuration producer must not return null.");

Try / catch

try { await annotation.ProduceAsync(context); }
catch (InvalidOperationException ex) when (ex.Message.Contains("launch configuration producer")) { logger.LogError(ex, "Producer for {Resource} returned null", context.ResourceName); }

Prevention

Return non-nullable LaunchConfiguration from producers so the compiler flags null paths
Throw on unsupported launch modes instead of returning null
Test producers for every launch mode the AppHost uses

When it happens

Trigger: A launchConfigurationProducer delegate whose awaited result is null — e.g. an async method returning null on a code path, a context lookup that misses, or a producer written as a lambda returning a null value.

Common situations: Producers that look up configurations by mode and return null for unknown modes, refactors that made a producer return nullable types, or factories returning null on error instead of throwing.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/c7d7ce79f78bf064. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/SupportsDebuggingAnnotation.cs:66

    internal Func<LaunchConfigurationCallbackContext, Task<object>> LaunchConfigurationProducer { get; }

    internal static SupportsDebuggingAnnotation Create<T>(
        string resourceName,
        string launchConfigurationType,
        Func<LaunchConfigurationCallbackContext, Task<T>> launchConfigurationProducer)
    {
        return new SupportsDebuggingAnnotation(
            launchConfigurationType,
            // The suppression is safe because ProduceAsync throws rather than returning null; the
            // compiler cannot see that because T is unconstrained and so may be a nullable type.
            async context => (await ProduceAsync(context).ConfigureAwait(false))!);

        async Task<T> ProduceAsync(LaunchConfigurationCallbackContext context)
        {
            var launchConfiguration = await launchConfigurationProducer(context).ConfigureAwait(false);
            if (launchConfiguration is null)
            {
                throw new InvalidOperationException(
                    $"The \"{launchConfigurationType}\" launch configuration producer for resource '{resourceName}' returned null. " +
                    $"The producer owns the complete launch configuration, so it must always return one.");
            }

            return launchConfiguration;
        }
    }
}

View on GitHub (pinned to 25830f84bd)