derailed/k9s · error

expected Unstructured, but got %T

Error message

expected Unstructured, but got %T

What it means

The Service (svc) renderer only accepts Kubernetes objects as *unstructured.Unstructured. Render's type assertion `o.(*unstructured.Unstructured)` failed, so the caller passed a different Go type (typed struct, metav1.TableRow, map, or a pointer-of-pointer variant). This is a wiring/programming error in the code that feeds the renderer, not a cluster or data problem.

Source

Thrown at internal/render/svc.go:47

	model1.HeaderColumn{Name: "VALID", Attrs: model1.Attrs{Wide: true}},
	model1.HeaderColumn{Name: "AGE", Attrs: model1.Attrs{Time: true}},
}

// Service renders a K8s Service to screen.
type Service struct {
	Base
}

// Header returns a header row.
func (s Service) Header(_ string) model1.Header {
	return s.doHeader(defaultSVCHeader)
}

// Render renders a K8s resource to screen.
func (s Service) Render(o any, _ string, row *model1.Row) error {
	raw, ok := o.(*unstructured.Unstructured)
	if !ok {
		return fmt.Errorf("expected Unstructured, but got %T", o)
	}
	if err := s.defaultRow(raw, row); err != nil {
		return err
	}
	if s.specs.isEmpty() {
		return nil
	}
	cols, err := s.specs.realize(raw, defaultSVCHeader, row)
	cols.hydrateRow(row)

	return err
}

func (s Service) defaultRow(raw *unstructured.Unstructured, r *model1.Row) error {
	var svc v1.Service
	err := runtime.DefaultUnstructuredConverter.FromUnstructured(raw.Object, &svc)
	if err != nil {
		return err

View on GitHub (pinned to 2d3ccc6ba2)

Solutions

1. Convert the object before rendering: runtime.DefaultUnstructuredConverter.ToUnstructured(obj) then wrap in &unstructured.Unstructured{Object: m}.
2. If the pipeline carries metav1.Table rows, switch to the Table renderer (Table.Render) instead of Service.Render.
3. Fix the caller: pass the row's original object (from cache/informer) unmodified instead of a transformed copy.
4. Log %T at the call site to identify exactly which type is being fed in, then normalize the producer side.

Example fix

// before
err := svc.Render(typedSvc, ns, row)

// after
m, _ := runtime.DefaultUnstructuredConverter.ToUnstructured(typedSvc)
err := svc.Render(&unstructured.Unstructured{Object: m}, ns, row)

u, ok := o.(*unstructured.Unstructured)
if !ok {
    m, conv := runtime.DefaultUnstructuredConverter.ToUnstructured(o)
    if !conv { return fmt.Errorf("cannot convert %T to unstructured", o) }
    u = &unstructured.Unstructured{Object: m}
}
err := svc.Render(u, ns, row)

func asUnstructured(o any) (*unstructured.Unstructured, bool) {
    switch v := o.(type) {
    case *unstructured.Unstructured:
        return v, true
    case unstructured.Unstructured:
        return &v, true
    default:
        return nil, false
    }
}

if err := svc.Render(obj, ns, row); err != nil {
    if strings.Contains(err.Error(), "expected Unstructured") {
    slog.Error("renderer type mismatch", "actualType", fmt.Sprintf("%T", obj))
    }
}

When it happens

Trigger: Calling Service.Render(o, ns, row) with anything other than *unstructured.Unstructured, e.g. a *corev1.Service, a metav1.TableRow coming from a server-side Table response, or a raw map[string]interface{}. Typically happens in custom ResourceViewers, Decorators, or after upgrading client-go where the informer/cache path starts delivering typed or Table objects.

Common situations: Writing a custom viewer that wraps objects before delegating to the svc renderer; switching a browser's data source from informer cache (unstructured) to metav1.Table (Server-Side Table print); version upgrades of k8s.io/client-go changing what the dynamic client returns.

Related errors

• expected TableRow, but got %T
• expected WorkloadRes but got %T
• no context for gvr found
• expecting context Path
• expecting a ForwardRes but got %T

AI-assisted analysis of derailed/k9s@2d3ccc6ba2 (2026-08-15). Data as JSON: /api/errors/ffdc3585ba358bcf. Report an issue: GitHub.