microsoft/aspire · error · InvalidOperationException

WithBuildScript requires a Deno package manager. Add a…

Error message

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

What it means

WithBuildScript emits a `deno task build`-style RUN step into the generated Dockerfile, which requires a package-manager annotation. During Dockerfile generation in AddDenoApp, if the resource has a JavaScriptBuildScriptAnnotation but no JavaScriptPackageManagerAnnotation, the library cannot build the command and throws.

Solutions

Call WithDeno() on the resource so the Deno package manager annotation is set.
Add a deno.json file to the app directory so package management is detected.
Remove WithBuildScript if no build step is actually needed for the container image.

Example fix

// before
builder.AddJavaScriptApp("svc", "main.ts").WithBuildScript("compile");
// after
builder.AddJavaScriptApp("svc", "main.ts").WithDeno().WithBuildScript("compile");

Defensive patterns

Strategy: validation

Validate before calling

// ensure a package manager is configured before WithBuildScript
if (!resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out _))
{
    resource.WithDeno(); // or add a deno.json to the app directory
}

Try / catch

try
{
    app.WithDeno().WithBuildScript("compile");
}
catch (InvalidOperationException ex) when (ex.Message.Contains("WithBuildScript requires a Deno package manager"))
{
    // configure Deno package management before the build script
}

Prevention

Configure the package manager (WithDeno or deno.json) before adding build scripts.
Do not copy WithBuildScript usage from npm examples onto unconfigured Deno resources.
Confirm the app directory has deno.json when relying on auto-detection.

When it happens

Trigger: Calling WithBuildScript("...") on a Deno/JavaScript app that lacks a package manager configuration — no deno.json detected and no WithDeno() called — then generating the Dockerfile.

Common situations: A Deno project without deno.json; adding WithBuildScript copied from an npm sample without the equivalent npm setup; build-script helper applied conditionally and package-manager detection skipped.

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/6d88858cc94f30f2. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.JavaScript/JavaScriptHostingExtensions.cs:964

                        var denoCacheCommand = BuildDenoCacheCommand(dockerfileContext.Resource, scriptPath, resource.WorkingDirectory);
                        buildStage
                            .EmptyLine()
                            // Pin DENO_DIR to a deterministic path so the runtime stage can copy the cache
                            // regardless of the base image's own default. The official denoland/deno image
                            // already uses /deno-dir, but a custom build image (WithDockerfileBaseImage) may not.
                            .Env("DENO_DIR", "/deno-dir")
                            .EmptyLine()
                            .WorkDir("/app")
                            .Copy(".", ".")
                            .EmptyLine()
                            .Run(denoCacheCommand);
                    }

                    if (dockerfileContext.Resource.TryGetLastAnnotation<JavaScriptBuildScriptAnnotation>(out var buildCommand))
                    {
                        if (!dockerfileContext.Resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var packageManager))
                        {
                            throw new InvalidOperationException("WithBuildScript requires a Deno package manager. Add a deno.json file or call WithDeno().");
                        }

                        buildStage
                            .EmptyLine()
                            .Run(BuildPackageScriptCommand(packageManager, buildCommand));
                    }

                    var logger = dockerfileContext.Services.GetService<ILogger<JavaScriptAppResource>>();
                    dockerfileContext.Builder.AddContainerFilesStages(dockerfileContext.Resource, logger);

                    var hasCustomRuntimeImage = baseImageAnnotation?.RuntimeImage is not null;
                    var baseRuntimeImage = baseImageAnnotation?.RuntimeImage ?? DefaultDenoImage;
                    var runtimeStage = dockerfileContext.Builder
                        .From(baseRuntimeImage, "runtime")
                            .EmptyLine()
                            // Match the build stage's DENO_DIR so the copied cache is discovered at runtime.
                            .Env("DENO_DIR", "/deno-dir")
                            .EmptyLine()

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