Distinguish between blank string flag and absence of flag

[Gerg]

Feature Request

It would be useful if there was a way to distinguish between passing a string flag a blank string (command -f "") and the absence of the flag (command).

Currently both will return "" from c.String("f")

Our use case:

We have a command to update a resource via an API. Fields that can be updated are represented by different CLI flags. One of the fields on the resource is a string that can be blank. We would like users to be able to set the field to the blank string.

#Setting the field to non-blank string
command -f "string"

#Setting the field to blank string
command -f ""

To do this currently we have to have another flag to reset the field.

command --clear-field

This is annoying because it means we have two flags for a single field and have to handle cases where both flags are passed.

Thanks!

[jszwedko]

@Gerg you should be able to utilize c.IsSet and c.GlobalIsSet for this -- let me know if that helps.

[Gerg]

That is exactly what I'm looking for! Thanks 🎉

[feliksik]

c.IsSet() requires you to manually check this and generate an appropiate error message; would it make sense to delegate this to the parser as well, by setting a { Required = true } field in the generator struct of the Flag?

[jszwedko]

@feliksik there has been some talk about required flags, you can see #155 for the latest. Help wanted to take that over the finish line.