Function needsServerInfo

cli/command/system/info.go:152–186

needsServerInfo detects if the given template uses any server information. If only client-side information is used in the template, we can skip connecting to the daemon. This allows (e.g.) to only get cli-plugin information, without also making a (potentially expensive) API call.

(template string, info dockerInfo)

// connecting to the daemon. This allows (e.g.) to only get cli-plugin
// information, without also making a (potentially expensive) API call.
func needsServerInfo(template string, info dockerInfo) bool {
	switch template {
	case "", formatter.JSONFormat, formatter.JSONFormatKey:
		// No format (default) and full JSON output need server-side info.
		return true
	default:
		if placeHolders.FindString(template) == "" {
			// The template does not contain formatting fields; assume we
			// need server-side information to render it, and return early.
			return true
		}
	}

	// A template is provided and has at least one field set.
	tmpl, err := templates.Parse(template)
	if err != nil {
		// ignore parsing errors here, and let regular code handle them
		return true
	}

	type sparseInfo struct {
		ClientInfo   *clientInfo `json:",omitempty"`
		ClientErrors []string    `json:",omitempty"`
	}

	// This constructs an "info" object that only has the client-side fields.
	err = tmpl.Execute(io.Discard, sparseInfo{
		ClientInfo:   info.ClientInfo,
		ClientErrors: info.ClientErrors,
	})
	// If executing the template failed, it means the template needs
	// server-side information as well. If it succeeded without server-side
	// information, we don't need to make API calls to collect that information.
	return err != nil
}

func prettyPrintInfo(streams command.Streams, info dockerInfo) error {
	// Only append the platform info if it's not empty, to prevent printing a trailing space.