Fish Shell argparse Doing Something Very Unexpected

Question

I'm running fish 3.1.0 on OS X 10.14.5.

I am new to fish and to argparse. I like them both.

The following simple test code:

#!/usr/local/bin/fish

function afoo 
    set -l options (fish_opt -s h -l help)
    set options $options (fish_opt -s m -l max --required-val)
    set options $options (fish_opt -s n -l nnn --optional-val)

    argparse $options -- $argv

    echo "max" $_flag_max
    echo "nnn" $_flag_nnn
end

Should create two switches m and n. m must take a value while n can take a value.

Here is a simple screen grab when testing that rudimentary function in Terminal's CLI:

[/usr/local/bin/fish 3.1.0] ~ afoo -m foo -n baz
max foo
nnn
[/usr/local/bin/fish 3.1.0] ~ afoo -mfoo -nbaz
max foo
nnn baz
[/usr/local/bin/fish 3.1.0] ~ 

Why does argparse not parse the space between the -n switch and its parameter but it does parse the space between the -m switch and its parameter?

This is driving me nuts. I've read the documentation a dozen times. What am I doing wrong?

PS The order of the switches doesn't matter.

Answer 1

Why does argparse not parse the space between the -n switch and its parameter but it does parse the space between the -m switch and its parameter?

The -n takes an optional parameter. Those have to, by getopt convention, be directly attached to the option argument.

Look at eg

echo never | grep --color never

This won't disable color, instead it will set color to auto (the default no-argument value) and look for the string "never". So it will show you "never" in red. Instead you'd have to use --color=never (or if it had a short option "-c" then "-cnever" would also be acceptable).

Argparse acts like the usual unix getopt(3) option parsing, which it also uses under the covers, because that's how the rest of the system acts.

Answer 2

This is because n/nnn=? has an optional parameter, whereas m/max= has a required one. Those strings are the output of your calls to fish_opt .

Non-option arguments are stored in $argv after a successful run of argparse . So your baz ends up in $argv .

Answer 3

Excellent, Thanks so very. very much.

If you're a newbie like me you can find more detail about what these answers point to by searching stack overflow for 'getopt space optional argument'.