docker/cli · error

invalid type %T for external

Error message

invalid type %T for external

What it means

Error "invalid type %T for external" thrown in docker/cli.

Source

Thrown at cli/compose/loader/loader.go:703

var transformMapStringString TransformerFunc = func(data any) (any, error) {
	switch value := data.(type) {
	case map[string]any:
		return toMapStringString(value, false), nil
	case map[string]string:
		return value, nil
	default:
		return data, fmt.Errorf("invalid type %T for map[string]string", value)
	}
}

var transformExternal TransformerFunc = func(data any) (any, error) {
	switch value := data.(type) {
	case bool:
		return map[string]any{"external": value}, nil
	case map[string]any:
		return map[string]any{"external": true, "name": value["name"]}, nil
	default:
		return data, fmt.Errorf("invalid type %T for external", value)
	}
}

var transformServicePort TransformerFunc = func(data any) (any, error) {
	switch entries := data.(type) {
	case []any:
		// We process the list instead of individual items here.
		// The reason is that one entry might be mapped to multiple ServicePortConfig.
		// Therefore we take an input of a list and return an output of a list.
		ports := []any{}
		for _, entry := range entries {
			switch value := entry.(type) {
			case int:
				v, err := toServicePortConfigs(strconv.Itoa(value))
				if err != nil {
					return data, err
				}
				ports = append(ports, v...)

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cli/compose/loader/loader.go:703 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/3e337909c01153e2.json. Report an issue: GitHub.