microsoft/aspire · error · InvalidOperationException

Generated Deno Dockerfiles do not support alternate package…

Error message

Generated Deno Dockerfiles do not support alternate package manager '{packageManager.ExecutableName}'. Use WithDeno() or provide a custom Dockerfile.

What it means

The generated Deno Dockerfile assumes the package manager is deno itself. If the resource has a JavaScriptPackageManagerAnnotation whose ExecutableName is not "deno" (e.g. npm, pnpm, yarn, bun), the generated image cannot run it, so ThrowIfUnsupportedDenoDockerfileOptions throws at build/publish time.

Solutions

Remove the alternate package manager configuration (WithNpm/WithPnpm/WithYarn/WithBun) from the resource.
Call WithDeno() to explicitly select Deno and the generated Deno Dockerfile path.
Provide a custom Dockerfile if you genuinely need another package manager inside the image.

Example fix

// before
builder.AddJavaScriptApp("api", "main.ts").WithNpm();
// after
builder.AddJavaScriptApp("api", "main.ts").WithDeno();

Defensive patterns

Strategy: validation

Validate before calling

// ensure the package manager is deno before relying on generated Deno Dockerfiles
if (resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var pm) &&
    !string.Equals(pm.ExecutableName, "deno", StringComparison.Ordinal))
{
    throw new InvalidOperationException($"{pm.ExecutableName} is not supported by generated Deno Dockerfiles.");
}

Try / catch

try
{
    resourceBuilder.WithDeno();
}
catch (InvalidOperationException ex) when (ex.Message.Contains("alternate package manager"))
{
    // drop the npm/pnpm/yarn/bun annotation or use a custom Dockerfile
}

Prevention

Check whether the project directory contains package.json before choosing Deno; auto-detection may pick npm.
Explicitly call WithDeno() instead of relying on inference when the app is Deno-based.
Only one package manager per resource — remove prior WithNpm/WithPnpm calls.

When it happens

Trigger: Configuring a resource whose Dockerfile is Deno-generated while a non-deno package manager annotation is present — e.g. calling WithNpm()/WithPnpm() (or the package manager being inferred from package.json) on a resource built via WithDeno(), then generating the Dockerfile.

Common situations: A project folder contains package.json so Aspire auto-detects npm while the developer also calls WithDeno(); switching a shared resource between package managers without removing the old annotation.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/bf749a77c2affa71. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.JavaScript/DenoHostingExtensions.cs:960

        NormalizeDenoContainerPathArguments(entrypoint);
        return [.. entrypoint];
    }

    private static void ThrowIfUnsupportedDenoDockerfileOptions(IResource resource)
    {
        if (resource.TryGetLastAnnotation<JavaScriptPublishModeAnnotation>(out var publishMode) &&
            publishMode.Mode is JavaScriptPublishMode.StaticWebsite or JavaScriptPublishMode.NodeServer)
        {
            var publishMethod = publishMode.Mode == JavaScriptPublishMode.StaticWebsite
                ? nameof(PublishAsStaticWebsite)
                : nameof(PublishAsNodeServer);
            throw new InvalidOperationException($"Generated Deno Dockerfiles do not support {publishMethod}. Use AddJavaScriptApp(...).WithDeno() or provide a custom Dockerfile.");
        }

        if (resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var packageManager) &&
            !string.Equals(packageManager.ExecutableName, "deno", StringComparison.Ordinal))
        {
            throw new InvalidOperationException($"Generated Deno Dockerfiles do not support alternate package manager '{packageManager.ExecutableName}'. Use WithDeno() or provide a custom Dockerfile.");
        }

        if (resource.TryGetLastAnnotation<DenoCommandLineAnnotation>(out var deno) &&
            deno.NodeModulesDirSet &&
            deno.NodeModulesDirMode == DenoNodeModulesDirMode.Manual)
        {
            throw new InvalidOperationException("The 'manual' node_modules mode is not supported by generated Deno Dockerfiles because node_modules is excluded from the build context. Use the 'auto' mode or provide a custom Dockerfile.");
        }

        if (deno is not null)
        {
            if (deno.RuntimeArgs.Any(argument =>
                argument == "--env-file" ||
                argument.StartsWith("--env-file=", StringComparison.Ordinal)))
            {
                throw new InvalidOperationException(
                    "Generated Deno Dockerfiles do not support '--env-file' because dotenv files can contain secrets that would be copied into the container image. Use Aspire environment variables or secret parameters, or provide a custom Dockerfile that handles the file securely.");
            }

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