Can't pass in an empty string to an option

[Summertime]

commandline:
    option variableA, string, "var", "v", "default"

# none of the following work
executable --var:
# out: Missing value for option 'var'
executable --var=
# out: Missing value for option 'var'
executable --var ""
# out: Couldn't convert '' to string

There should only be an error if the user hasn't explicitly given a blank value, like the following

executable --var
# out: Missing value for option 'var'

[fenekku]

I have been thinking about this for a while now. I agree we need a way to override a default string option to a given empty string... but it is non-trivial. I say that because of the following:

1- there is a need to establish what we want -- studying the behaviour of other classic CLI (C/Python) would be the next step (see below)
2- the basic CLI parsing is controlled by the underlying parseopt standard library -- implementing our own or contributing to the standard library might be needed
3- the standard library has at least one bug (see below)

CLI	should do	does
--option="" tree	option == "" and argument == "tree"	option == "tree" argument missing
--option='' tree	option == "" and argument == "tree"	option == "tree" argument missing
--option "" tree	option == "" and argument == "tree"	couldn't convert '' to string for option
--option= tree	missing option for --option OR option == "" OR option == "tree"	option == "tree" argument missing
--option="" --anotherOption tree	option == "" and argument == "tree"	option == "--anotherOption" argument == "tree" -- this is a bug in the standard library
--option= --anotherOption tree	missing option for --option OR option == "" OR option == "--anotherOption" and argument == "tree"	option == "--anotherOption" argument == "tree"
--option --anotherOption tree	missing option for --option OR option == "" and argument == "tree"	missing value for option 'option'

For all the "should do" with "OR" cases, we would need to look at how it is done typically and if it makes sense.

[Summertime]

Some links for reference

POSIX's rough guide

The primary Python framework Click

The stdlib for Python3

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The nim stdlib parseopt seems to be very reminiscent of getopt which has always been fairly restrictive (POSIX only requires single letter flags/options, so the tooling for that has been similarly limited), so probably opting for a custom parsing library would give the best sanest result

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Also worth noting that the argument passing mechanisms differ between OSes. (e.g. windows doesn't really have an understanding of what quoting is) so that is a potential issue