docker/cli · error

cannot merge configs: %w

Error message

cannot merge configs: %w

What it means

Error "cannot merge configs: %w" thrown in docker/cli.

Source

Thrown at cli/compose/loader/merge.go:48

	base := configs[0]
	for _, override := range configs[1:] {
		var errs []error
		if services, err := mergeServices(base.Services, override.Services); err != nil {
			errs = append(errs, fmt.Errorf("cannot merge services: %w", err))
		} else {
			base.Services = services
		}
		if err := mergo.Map(&base.Volumes, &override.Volumes, mergo.WithOverride); err != nil {
			errs = append(errs, fmt.Errorf("cannot merge volumes: %w", err))
		}
		if err := mergo.Map(&base.Networks, &override.Networks, mergo.WithOverride); err != nil {
			errs = append(errs, fmt.Errorf("cannot merge networks: %w", err))
		}
		if err := mergo.Map(&base.Secrets, &override.Secrets, mergo.WithOverride); err != nil {
			errs = append(errs, fmt.Errorf("cannot merge secrets: %w", err))
		}
		if err := mergo.Map(&base.Configs, &override.Configs, mergo.WithOverride); err != nil {
			errs = append(errs, fmt.Errorf("cannot merge configs: %w", err))
		}
		if err := errors.Join(errs...); err != nil {
			return nil, errors.Join(fmt.Errorf("failed to merge file %s", override.Filename), err)
		}
	}
	return base, nil
}

func mergeServices(base, override []types.ServiceConfig) ([]types.ServiceConfig, error) {
	mergeOpts := []func(*mergo.Config){
		mergo.WithAppendSlice,
		mergo.WithOverride,
		mergo.WithTransformers(&specials{m: map[reflect.Type]func(dst, src reflect.Value) error{
			reflect.PointerTo(reflect.TypeFor[types.LoggingConfig]()):        safelyMerge(mergeLoggingConfig),
			reflect.TypeFor[[]types.ServicePortConfig]():                     mergeSlice(toServicePortConfigsMap, toServicePortConfigsSlice),
			reflect.TypeFor[[]types.ServiceSecretConfig]():                   mergeSlice(toServiceSecretConfigsMap, toServiceSecretConfigsSlice),
			reflect.TypeFor[[]types.ServiceConfigObjConfig]():                mergeSlice(toServiceConfigObjConfigsMap, toSServiceConfigObjConfigsSlice),
			reflect.PointerTo(reflect.TypeFor[types.UlimitsConfig]()):        mergeUlimitsConfig,

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cli/compose/loader/merge.go:48 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/ba2865d3557598a3.json. Report an issue: GitHub.