microsoft/aspire · error

aspire: dict.toObject: unexpected result type %T

Error message

aspire: dict.toObject: unexpected result type %T

What it means

Dict.ToObject invokes the getter capability and expects a map[string]any snapshot of the dictionary. If the transport returns another type (e.g. a handle reference instead of a full value snapshot), ToObject fails with this message including the actual type.

Solutions

1. Regenerate the Go resource bindings to match the running AppHost.
2. Log the actual result type from the error message and compare with the documented response shape for toObject.
3. Ensure the dict is materializable (not a lazy handle-only reference) before calling ToObject.
4. Upgrade/downgrade the aspire Go package so both sides share the same protocol.

Example fix

// before
m, ok := result.(map[string]any)
if !ok {
    return nil, fmt.Errorf("aspire: dict.toObject: unexpected result type %T", result)
}
// after
result, err := invokeGetter(ctx, d.getterCapabilityID)
if err != nil { return err }
if h, isHandle := result.(handleReference); isHandle {
    return nil, fmt.Errorf("dict is a lazy handle (%s); call Get per key instead of ToObject", h.id)
}

func asValueMap(v any) (map[string]any, bool) { m, ok := v.(map[string]any); return m, ok }

obj, err := dict.ToObject(ctx)
if err != nil {
    // fall back to per-key access
    v, getErr := dict.Get(ctx, "key")
    if getErr != nil { return getErr }
    _ = v
}

When it happens

Trigger: Calling ToObject on an AspireDictValue when the AppHost responds with a non-map payload — usually when the getter resolves to a handle rather than materializing values, or the response shape changed between versions.

Common situations: Version drift between generated Go code and AppHost, custom getter returning nested/handle results, transport layer mapping the response to an unexpected concrete type.

Related errors

• aspire: dict getter returned unexpected type %T
• aspire: list getter returned unexpected type %T
• aspire: merge type mismatch: cannot merge
• aspire: : parameter must be one of [ ], got %T
• callback ID missing

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/85e75ed6e23f73a4. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.CodeGeneration.Go/Resources/base.go:574

	}
	return vals, nil
}

func (d *Dict[K, V]) ToObject() (map[string]V, error) {
	ctx := context.Background()
	h, err := d.resolveDictHandle(ctx)
	if err != nil {
		return nil, err
	}
	result, err := d.parent.client.invokeCapability(ctx, "Aspire.Hosting/Dict.toObject", map[string]any{
		"dict": h.ToJSON(),
	})
	if err != nil {
		return nil, err
	}
	m, ok := result.(map[string]any)
	if !ok {
		return nil, fmt.Errorf("aspire: dict.toObject: unexpected result type %T", result)
	}
	obj := make(map[string]V, len(m))
	for k, raw := range m {
		v, err := decodeAs[V](raw)
		if err != nil {
			return nil, err
		}
		obj[k] = v
	}
	return obj, nil
}

func (d *Dict[K, V]) Set(key K, value V) error {
	ctx := context.Background()
	h, err := d.resolveDictHandle(ctx)
	if err != nil {
		return err
	}

View on GitHub (pinned to 25830f84bd)