Command: RedirectTo

Redirecting root command to a subcmd

.SetRedirectTo(subcmd) provides a new target for the Root Command.

Redirecting root command to a subcmd, can be used at this scene, makes an input commandline app worked as app a b c, when the .SetRedirectTo("a.b.c") setup.

The well-known case is pnpm, a nodejs package manager, which can forward any unmatched commands like pnpm dev to pnpm run ..., that would be pnpm run dev.

Definitions

The key interface is *CmdS.SetRedirectTo(dottedCmdPath). So whatever we need to do is,

func main() {
	app := cmdr.Create(appName, version, author, desc).With(func(app cli.App) {
		// redirect root commands into "wrong" subcmd for testing.
		//
		// For a dad command such as "server" command, it
		// would translate `app start|stop` -> `app server start|stop`.
		app.WithRootCommand(func(root *cli.RootCommand) {
			root.SetRedirectTo("wrong")
		})
	}).WithAdders(cmd.Commands...).Build()
 
	ctx := context.Background()
	if err := app.Run(ctx); err != nil {
		logz.ErrorContext(ctx, "Application Error:", "err", err) // stacktrace if in debug mode/build
		os.Exit(app.SuggestRetCode())
	} else if rc := app.SuggestRetCode(); rc != 0 {
		os.Exit(rc)
	}
}

The full codes are in examples/redirect-to-subcmd.

In this example, WithAdders(...) will attach two subcmds into app: jump to and wrong.

And With(func(app cli.App){...}) closure block would give you a challenge to operate app object in a streaming call.

It is the right position to calling to SetRedirectTo().

As it ran, end-user's app will have the same effect with typing app wrong in command line.

Multiple Subcmds

To rediect into a multi-level subcmd as target, you can using dottedPath. The dottedPath allows a single string to represent the multi-level subcmds. So SetRedirectTo("jump.to") could point to the target jump/to subcmd.

Run

The result of example app is,

$ go run ./examples/redirect-to-subcmd
the duration is: 0s
22:57:12.597014+08:00| [ERR] Application Error:                   err="[io: read/write on closed pipe | something's wrong | permission denied]" ./examples/redirect-to-subcmd/main.go:38 main.main
$

The returning Application Error is the response of the subcmd wrong.

Note that the default action of root command is not work any more. So you must request the root help screen by typing app -h or app --help explicitly.

额外的话题