unable to parse assets as assetBuilder is not defined

Error message

unable to parse assets as assetBuilder is not defined

What it means

Image() builds the docker image reference for a kOps component, but resolving an image may require rewriting/verifying assets, which needs an AssetBuilder. The function guards against a nil assetsBuilder and refuses to run, returning this error instead of panicking on a nil pointer.

Source

Thrown at pkg/model/components/context.go:139

		baseIPInt := big.NewInt(0)
		baseIPInt.SetBytes(ip6)
		serviceIPInt := big.NewInt(0)
		serviceIPInt.Add(big.NewInt(int64(id)), baseIPInt)
		serviceIP := make(net.IP, len(ip6))
		serviceIPBytes := serviceIPInt.Bytes()
		for i := range serviceIPBytes {
			serviceIP[len(serviceIP)-len(serviceIPBytes)+i] = serviceIPBytes[i]
		}
		return serviceIP, nil
	}

	return nil, fmt.Errorf("unexpected IP address type for ServiceClusterIPRange: %s", networkingSpec.ServiceClusterIPRange)
}

// Image returns the docker image name for the specified component
func Image(component string, clusterSpec *kops.ClusterSpec, assetsBuilder *assets.AssetBuilder) (string, error) {
	if assetsBuilder == nil {
		return "", fmt.Errorf("unable to parse assets as assetBuilder is not defined")
	}

	kubernetesVersion, err := kopsmodel.ParseKubernetesVersion(clusterSpec.KubernetesVersion)
	if err != nil {
		return "", err
	}

	imageName := component

	if !kubernetesVersion.IsBaseURL() {
		image := "registry.k8s.io/" + imageName + ":" + "v" + kubernetesVersion.String()

		return assetsBuilder.RemapImage(image), nil
	}

	// The simple name is valid when pulling.  But if we
	// are loading from a tarfile then the image is tagged with
	// the architecture suffix.

View on GitHub (pinned to 4c8573c808)

Solutions

Pass a valid *assets.AssetBuilder (e.g. built via BuildOptions / assetutils.RecommendAssets) instead of nil
If assets are irrelevant for your case, compute the image name manually or use the default image path that does not require asset rewriting
In tests, construct a minimal AssetBuilder or use the existing TestImage harness that supplies one

Example fix

// before
img, err := components.Image("kube-apiserver", clusterSpec, nil)
// after
assetsBuilder := assets.NewAssetBuilder(assetsLocation, kubernetesVersion, false)
img, err := components.Image("kube-apiserver", clusterSpec, assetsBuilder)

Defensive patterns

Strategy: validation

Validate before calling

if assetsBuilder == nil {
    return fmt.Errorf("assetsBuilder must be constructed before calling components.Image")
}

Type guard

func hasAssetBuilder(b *assets.AssetBuilder) bool { return b != nil }

Try / catch

img, err := components.Image(component, clusterSpec, assetsBuilder)
if err != nil {
    return fmt.Errorf("resolving image for %s: %w", component, err)
}

Prevention

Always obtain the AssetBuilder from BuildOptions rather than constructing ad-hoc
Add nil checks at call sites that receive a builder from upstream code
Keep tests using the existing harness that supplies a builder

When it happens

Trigger: Calling components.Image(component, clusterSpec, nil) — e.g. when a caller such as BuildOptions skips asset construction or a test passes no builder — and the component image cannot be resolved without the builder.

Common situations: Custom code or tests invoking Image() directly without building assets via assetutils/build options; refactored call sites that dropped the AssetBuilder argument; partial initialization of build options.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/0b8e2ebfbdfd3de0. Report an issue: GitHub.