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No way to make the value of an option optional

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
lua
Domain
cli

Research direction

Start with the option declaration and parsing calls shown in optopt.lua, especially cli:option("-f, --foo=[VALUE]", ...) and cli:parse(_G.arg). Trace how an option with no supplied value is handled, then verify that an omitted flag, a bare -f, and -f buz produce the three outcomes described in the issue.

Written by the indexing model from the issue text.

Description

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
Dominant language
Lua
Stars
129
Forks
26
Avg merge
1h 41m
Merged PRs (30d)
1

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