microsoft/aspire · error · InvalidOperationException

The published Rust app

Error message

The published Rust app '{resource.Name}' was not converted to a container resource.

What it means

FinalizePublishDockerfile re-creates a builder for the container resource created during publish. If TryCreateResourceBuilder<ContainerResource> cannot find or create the builder for resource.Name, the later annotation checks cannot proceed and this InvalidOperationException is thrown.

Solutions

Audit AppHost custom transformations for anything removing/renaming the Rust container resource.
Ensure resource names are unique across the AppHost.
Recreate the resource with AddRustApp so the full publish pipeline (conversion + finalization) runs.
If the transformation order looks correct, minimize to a repro and report with Aspire version.

Defensive patterns

Strategy: validation

Validate before calling

var containerExists = applicationBuilder.Resources.OfType<ContainerResource>().Any(r => r.Name == resource.Name);
if (!containerExists) throw new InvalidOperationException("Rust container resource missing before publish finalization");

Try / catch

try { PublishAsync(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("was not converted to a container resource")) {
    logger.LogError("Model transformation lost the Rust container resource; audit transformations");
}

Prevention

Audit custom IResourceTransformation callbacks
Avoid renaming resources between creation and publish
Use AddRustApp end-to-end rather than hand-building the resource

When it happens

Trigger: During publish mode finalization of a Rust app: the container resource with the Rust resource's name is absent from applicationBuilder.Resources — typically because model transformation to ContainerResource never happened or the resource was removed/renamed by custom callbacks.

Common situations: Custom IResourceTransformation removing or renaming resources; duplicate names breaking the builder lookup; calling publish APIs on resources not created by AddRustApp; library bug after upgrading Aspire versions.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/5a41237b45bb2291. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.Rust/RustHostingExtensions.cs:728

        // https://github.com/microsoft/aspire/issues/18956.
        // See https://doc.rust-lang.org/cargo/reference/config.html#buildtarget
        if (target.Target is null && environment.TryGetValue("CARGO_BUILD_TARGET", out var buildTarget) && buildTarget.Length > 0)
        {
            target = target with { Target = buildTarget };
        }

        return target.GetExecutablePath(metadata.TargetDirectory);
    }

    private static void FinalizePublishDockerfile(
        IDistributedApplicationBuilder applicationBuilder,
        RustAppResource resource,
        DockerfileBuildAnnotation provisionalDockerfile,
        RustPublishState publishState)
    {
        if (!applicationBuilder.TryCreateResourceBuilder<ContainerResource>(resource.Name, out var containerBuilder))
        {
            throw new InvalidOperationException(
                $"The published Rust app '{resource.Name}' was not converted to a container resource.");
        }

        var annotations = containerBuilder.Resource.Annotations;
        if (!containerBuilder.Resource.TryGetLastAnnotation<DockerfileBuildAnnotation>(out var activeDockerfile)
            || !ReferenceEquals(activeDockerfile, provisionalDockerfile))
        {
            // PublishAsDockerFile is idempotent, so callers can replace the integration's provisional
            // Dockerfile or factory after AddRustApp returns. That later configuration owns its context,
            // generated content, platform, and target handling.
            return;
        }

        ContainerTargetPlatform? targetPlatform = null;

        annotations.Remove(provisionalDockerfile);

        var workingDirectory = Path.GetFullPath(resource.WorkingDirectory);

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