microsoft/aspire · error · InvalidOperationException

PublishAsPackageScript requires a Deno package manager. Add…

Error message

PublishAsPackageScript requires a Deno package manager. Add a deno.json file or call WithDeno().

What it means

PublishAsPackageScript (JavaScriptPublishMode.PackageScript) for a Deno app depends on package-manager and install-command annotations that only exist when Deno package management is configured. During Dockerfile generation in AddDenoApp, if those annotations are missing, the library cannot emit the package-script build stage and throws.

Solutions

Add a deno.json file to the application directory so the Deno package manager is detected.
Call WithDeno() on the resource to configure Deno package management explicitly.
Remove PublishAsPackageScript() if the resource is not actually a Deno package-script app.

Example fix

// before
builder.AddJavaScriptApp("pkg", "main.ts").PublishAsPackageScript();
// after
builder.AddJavaScriptApp("pkg", "main.ts").WithDeno().PublishAsPackageScript();

Defensive patterns

Strategy: validation

Validate before calling

// ensure Deno package management exists before PublishAsPackageScript
if (!resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out _) ||
    !resource.TryGetLastAnnotation<JavaScriptInstallCommandAnnotation>(out _))
{
    resource.WithDeno(); // or ensure a deno.json exists in the app directory
}

Try / catch

try
{
    app.WithDeno().PublishAsPackageScript();
}
catch (InvalidOperationException ex) when (ex.Message.Contains("PublishAsPackageScript requires a Deno package manager"))
{
    // add deno.json or call WithDeno() first
}

Prevention

Always create a deno.json in Deno projects so package management is detectable.
Chain WithDeno() before PublishAsPackageScript() as a habit.
Verify package-manager detection succeeded when using conditional resource setup.

When it happens

Trigger: Calling PublishAsPackageScript() on a JavaScript/Deno app resource that has no deno.json (so no Deno package manager annotation is inferred) and no explicit WithDeno() call, then generating its Dockerfile.

Common situations: A Deno project without a deno.json file relying on defaults; forgetting WithDeno() after applying PublishAsPackageScript; a resource where package-manager detection failed silently.

Understand the failure class

Background: "not installed", "pip install", "required for": how missing-dependency errors surface across open-source libraries — this error's family across 34 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/19d9bceacb309c84. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.JavaScript/JavaScriptHostingExtensions.cs:927

                    // Deno ships its own runtime, so both stages default to the same Deno image. Unlike the Bun
                    // variant there is no separate production-dependency install stage: Deno caches remote and
                    // npm dependencies under DENO_DIR. Direct run/serve entrypoints pre-populate that cache in
                    // the build stage and use --cached-only at runtime. Task entrypoints are opaque shell
                    // commands in deno.json, so Aspire cannot safely infer their module graph.
                    var baseBuildImage = baseImageAnnotation?.BuildImage ?? DefaultDenoImage;
                    var buildStage = dockerfileContext.Builder
                        .From(baseBuildImage, "build");

                    // Package-script builds install from the manifest layer before copying the remaining source.
                    // Direct run/serve builds copy the full module graph first, then cache it with the same
                    // resolution and lock flags used by the runtime entrypoint.
                    dockerfileContext.Resource.TryGetLastAnnotation<JavaScriptPublishModeAnnotation>(out var publishMode);
                    if (publishMode?.Mode == JavaScriptPublishMode.PackageScript)
                    {
                        if (!dockerfileContext.Resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var packageManager) ||
                            !dockerfileContext.Resource.TryGetLastAnnotation<JavaScriptInstallCommandAnnotation>(out var installCommand))
                        {
                            throw new InvalidOperationException("PublishAsPackageScript requires a Deno package manager. Add a deno.json file or call WithDeno().");
                        }

                        buildStage.EmptyLine();
                        packageManager.InitializeDockerBuildStage?.Invoke(buildStage);
                        buildStage
                            .EmptyLine()
                            .WorkDir("/app");

                        var copiedAllSource = buildStage.CopyPackageFilesForInstall(packageManager);
                        buildStage.AddInstallCommand(packageManager, installCommand);

                        if (!copiedAllSource)
                        {
                            buildStage.Copy(".", ".");
                        }
                    }
                    else
                    {

View on GitHub (pinned to 25830f84bd)