How do I most reasonably implement "-T[1]" ?

[shueybubbles]

I'm building a tool in Go whose command line has some backward compatibility requirements with the C++ version. It uses a Windows style without -- or commands.

One of the switches is of the form -T[1] where -T by itself means one thing and -T1 means T plus something else. The short tag seems limited to 1 character and name implies a -- usage.

I guess I can name a struct member T1 but then I have to make sure the struct member with the meaningful name gets set to its value after the kong processing has completed.

[smlx]

Could you just make -T a short flag with an optional argument, and then check the argument value at runtime? If it is 1, then the user passed -T1.

[alecthomas]

Code wise that would be compatible, but from a shell "API" perspective that would be a breaking change as -T by itself does not work in Kong. I assume that's more what @shueybubbles wants.

[alecthomas]

I'm not opposed to the idea of supporting this, but what would the value of the field be in the case of -T.

eg.

Count int `short:"T" optional:""`

It is clear what value Count will have for -T<int>, but what will it have for -T and how would that differ from not passing -T at all?

[shueybubbles]

The 1 isn't a count, it's a modifier.
Another example of this style is from the [sqlcmd] (https://docs.microsoft.com/sql/tools/sqlcmd-utility) tool. This tool has been around for decades so I'll reserve judgment on the choices made; command lines for Windows were generally adhoc back in the day.

-r[0 | 1]
Redirects the error message output to the screen (stderr). If you do not specify a parameter or if you specify 0, only error messages that have a severity level of 11 or higher are redirected. If you specify 1, all error message output including PRINT is redirected. Has no effect if you use -o. By default, messages are sent to stdout.

-k [1 | 2]
Removes all control characters, such as tabs and new line characters from the output. This parameter preserves column formatting when data is returned. If 1 is specified, the control characters are replaced by a single space. If 2 is specified, consecutive control characters are replaced by a single space. -k is the same as -k1.

As for consuming it in a struct I'm not even sure what's most intuitive. Perhaps a nested struct with a bool value to indicate whether it was set and an int for the argument.

type Args struct {
	RemoveControl struct {
		Set bool `short:"k" optional:"" `
		RemoveStyle int `arg:"" optional:"" default:"1"`
	}
 }