OptionParser with subcommands - ruby

Question

I'm trying to create a command line program with sub-commands using OptionParser. I'm following "ruby's OptionParser to get subcommands".
The problem is that it does not allow for a use case like this:
ruby main.rb --version
#=> main.rb in `<main>': undefined method `order!' for nil:NilClass (NoMethodError)
But it does allow for this:
ruby main.rb foo --options
ruby main.rb --options foo
ruby main.rb --options foo --options
How would I be properly handle command line arguments, in the case that no subcommand is given.
My example code is:
global = OptionParser.new do |opts|
opts.banner = "Usage: opt.rb [options] [subcommand [options]]"
opts.on("-v", "--version", "Print the version") do |v|
options[:version] = v
end
opts.separator ""
opts.separator subtext
end

Answer 1

The lines with the error:
global.order!
command = ARGV.shift
subcommands[command].order!
If global.order! uses all of ARGV, then command is nil. So... check for that.
global.order!
command = ARGV.shift
unless command
STDERR.puts "ERROR: no subcommand"
STDERR.puts global # prints usage
exit(-1)
end
subcommands[command].order!

Answer 2

Maybe this'll help:
require 'optparse'
VERSION = '1.0.0'
options = {}
OptionParser.new do |opt|
opt.on('-f', '--foo', 'Foo it') { |o| options[:foo] = o }
opt.on_tail('-v', '--version') do
puts VERSION
exit
end
end.parse!
puts options
Saving it as "test.rb" and running it with ruby test.rb returns:
{}
Running it with ruby test.rb -f or --foo returns:
{:foo=>true}
Running it with ruby test.rb -v or --version returns:
1.0.0
For more fun, running ruby test.rb -h or --help returns:
Usage: test [options]
-f, --foo Foo it
even though I didn't define -h or --help.
If I wanted the -v and --version flags to appear in the list then I'd change them from a on_tail method to a normal on method:
require 'optparse'
VERSION = '1.0.0'
options = {}
OptionParser.new do |opt|
opt.on('-f', '--foo', 'Foo it') { |o| options[:foo] = o }
opt.on('-v', '--version', 'Returns the version') do
puts VERSION
exit
end
end.parse!
puts options
which would return:
Usage: test [options]
-f, --foo Foo it
-v, --version Returns the version
I can add:
puts ARGV
to the end of the script and see that OptionParser is correctly handling flags and parameters:
>ruby test.rb bar --foo
{:foo=>true}
bar
>ruby test.rb --foo bar
{:foo=>true}
bar
See "Pass variables to Ruby script via command line" for more information.
There is no way your example code will handle your sample inputs using --options. No handler for --options is defined. Nor is subtext. Your code returns:
undefined local variable or method `subtext' for main:Object (NameError)
Stripping the block to:
global = OptionParser.new do |opts|
opts.on("-v", "--version", "Print the version") do |v|
options[:version] = v
end
end
and running again returns:
invalid option: --options (OptionParser::InvalidOption)
So, again, your example doesn't match the results you say you're getting.