docker/cli · error

got wrong object to inspect

Error message

got wrong object to inspect

What it means

Internal type-assertion failure in the service pretty-print path: inspectFormatWrite expects each object returned by the getRef callback to be a swarm.Service, and errors if the assertion `serviceI.(swarm.Service)` fails. It indicates the inspect plumbing handed a non-Service value (or a pointer instead of a value) to the service formatter — a programming/integration bug rather than a user mistake.

Source

Thrown at cli/command/service/formatter.go:235

	}
	return networkNames
}

// inspectFormatWrite renders the context for a list of services
func inspectFormatWrite(fmtCtx formatter.Context, refs []string, getRef, getNetwork inspect.GetRefFunc) error {
	if fmtCtx.Format != serviceInspectPrettyTemplate {
		return inspect.Inspect(fmtCtx.Output, refs, string(fmtCtx.Format), getRef)
	}

	return fmtCtx.Write(&serviceInspectContext{}, func(format func(subContext formatter.SubContext) error) error {
		for _, ref := range refs {
			serviceI, _, err := getRef(ref)
			if err != nil {
				return err
			}
			service, ok := serviceI.(swarm.Service)
			if !ok {
				return errors.New("got wrong object to inspect")
			}
			if err := format(&serviceInspectContext{
				Service:      service,
				networkNames: resolveNetworks(service, getNetwork),
			}); err != nil {
				return err
			}
		}
		return nil
	})
}

type serviceInspectContext struct {
	swarm.Service
	formatter.SubContext

	// networkNames is a map from network IDs (as found in
	// Networks[x].Target) to network names.

View on GitHub (pinned to e9452d6e78)

Solutions

1. If embedding the cli packages, ensure the getRef callback returns swarm.Service by value, not *swarm.Service or another type.
2. Align docker/cli and moby/moby client library versions so inspect result types match.
3. If hit from the stock docker binary, report it as a bug with `docker version` output — end users should never see this.

Example fix

// before (custom getRef)
return &res.Service, res.Raw, err
// after
return res.Service, res.Raw, err // value, matches serviceI.(swarm.Service)

When it happens

Trigger: Only reachable when the pretty template is active and getRef returns something other than a swarm.Service value — e.g. custom code embedding the docker/cli packages passes *swarm.Service or another type, or an API-version mismatch causes decoding into a different type.

Common situations: Developers vendoring github.com/docker/cli and wiring their own GetRefFunc into inspectFormatWrite, or version skew between cli and moby client libraries where the inspect result type changed (value vs pointer).

Related errors

• --format is incompatible with human friendly format
• cannot supply extra formatting options to the pretty templat
• tty service logs only supported with --raw
• placement preference must be of the format "<strategy>=<arg>
• invalid credential spec: value must be prefixed with "config

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/e303bb5f075a098c.json. Report an issue: GitHub.