No way to make the value of an option optional

[alerque]

In the 2.x series of releases it was possible to setup an option that had no value if not set, a default value if just the flag was added but no value given, and additionally a custom value if a value was passed. In 3.x this does not seem to be possible. Flags cannot take values and options always require a value. The default for options is only parsed in the event the option flag is not even passed.

As an example, I would like the value of a --foo=[VALUE] option to be optional with a default value if set, but allow the user to set (or not set) foo. If this is optopt.lua:

#!/usr/bin/env lua

local cli = require("cliargs")

cli:set_name("optopt")
cli:set_description("optional arg test")
cli:option("-f, --foo=[VALUE]", "foo val default to fiz", "fiz")
cli:flag("-h, --help", "display this help, then exit")

local opts, err = cli:parse(_G.arg)

if not opts and err then
  print(err)
  os.exit(1)
end

print("foo is", opts.foo)

What I get vs. what I expect:

# as expected
$ ./optopt.lua -f buz
foo is  buz

# unexpected, no option should mean no value
$ ./optopt.lua
foo is  fiz

# unexpected, setting the option should enable the default value if no value passed
$ ./optopt.lua -f
option -f requires a value to be set