Weird behaviour of BoolTFlag compared to BoolFlag

[osleg]

Given this snippet

func main() {

	// Setup initial stuff
	cl := cli.NewApp()

	// Define flags
	cl.Flags = []cli.Flag{
		cli.BoolTFlag{
			Name:  "daemon, d",
			Usage: "Controls whether to run in daemon mode",
		},
		cli.BoolFlag{
			Name:  "debug",
			Usage: "Enable debug output",
		},
	}

	cl.Action = func(c *cli.Context) error {
		fmt.Println("Daemon:", c.BoolT("daemon"))
		fmt.Println("Debug", c.Bool("debug"))

		return nil
	}

	cl.Run(os.Args)
}

The output of running the app without args is what I'm expecting

$ go build && ./monitor
Daemon: true
Debug false

But if I provide the flags the --daemon flag is ignored

$ go build && ./monitor --debug --daemon
Daemon: true
Debug true

Though if I provide --daemon=false it works as intended

$ go build && ./monitor --debug --daemon=false
Daemon: false
Debug true

Is this expected behaviour? --debug doesn't require the explicit true and acts like switch

[jszwedko]

Hi @osleg,

This is the expected behavior of BoolTFlag. It essentially functions the same as BoolFlag just with a default of true so =false is required for setting the flag to false (in the v2 branch it is actually dropped in lieu of just adding a .Value field to BoolFlag to set the default). You could consider a --no-daemon or --foreground flag if the default behavior is to run as a daemon.

Hope this helps!

[osleg]

Thanks for answer, thou this is a bit confusing since as it could be seen in the demo above the BoolFlag does not require =true to become truthful. Seems like BoolFlag can act as switch while BoolTFlag can't.
Would be nice to have this specified in docs, not a big issue tho :)

[jszwedko]

👍 I agree it is a bit confusing which is why I believe it's removal in v2 will be an improvement.

It is specified in the godoc for the package (https://godoc.org/github.com/urfave/cli#BoolTFlag), but let me know if you think the documentation there could be improved (or open a PR 😄 ).

Gonna close this out, but thanks for opening this discussion!

[osleg]

With pleasure, PR added ;)