OptionParser: unexpected behaviour with -help


#1

I ran into some unexpected behaviour with the Ruby OptionParser class.
When running this script (without any command line arguments) the output
is as in the last, commented, line.


require ‘optparse’
options = {}
OptionParser.new do |opt|
opt.on “–ex EXECUTABLE”, String do |val|
options[:ex] = val
end
opt.on “–headers” do |val|
options[:headers] = val
end
opt.parse(%w( -help ))
end

puts options.inspect

Output is {:ex=>“lp”, :headers=>true}


I don’t think that ‘-help’ should be treated the same as ‘-h -ex lp’ or
‘-h --ex lp’. In particular, ‘-help’ may be a misspelling of the
common ‘–help’ option. Am I doing something wrong? Is there a way to
avoid this?

Thanks a lot,

Stephan


#2

Look at the source - /usr/lib/ruby/1.8/optparse.rb or somewhere similar
on your system.

            # if no short options match, try completion with long
            # options.
            sw, = complete(:long, opt)

So it looks that if you stub out ‘complete’ you can get the behaviour
you require: that is, I think you want -h to be treated as an error
instead of as a shortcut for --headers, and ditto -e as an error instead
of a shortcut for --ex

Alternatively, if only ‘-help’ is a problem, you could just handle this
special case:

ARGV.each { |a| a.replace(’–help’) if a == ‘-help’ }


#3

On 24.05.2009 06:58, Stephan W. wrote:

options[:ex] = val

end
opt.on “–headers” do |val|
options[:headers] = val
end
opt.parse(%w( -help ))

In addition to what Brian wrote, the line above is wrongly placed IMHO.
You cannot know whether initialization of the OptionParser instance is
completed when still inside the block. You should rather invoke #parse
on the result of OptionParser.new.

end

puts options.inspect

Kind regards

robert


#4

Brian C. wrote:

Look at the source - /usr/lib/ruby/1.8/optparse.rb or somewhere similar
on your system.

            # if no short options match, try completion with long
            # options.
            sw, = complete(:long, opt)

So it looks that if you stub out ‘complete’ you can get the behaviour
you require: that is, I think you want -h to be treated as an error
instead of as a shortcut for --headers, and ditto -e as an error instead
of a shortcut for --ex

Alternatively, if only ‘-help’ is a problem, you could just handle this
special case:

ARGV.each { |a| a.replace(’–help’) if a == ‘-help’ }

Well, thanks a lot for that. I feel the guessing game should be avoided
– there’s too much potential for confusion.

Stephan


#5

Robert K. wrote:

On 24.05.2009 06:58, Stephan W. wrote:

options[:ex] = val

end
opt.on “–headers” do |val|
options[:headers] = val
end
opt.parse(%w( -help ))

In addition to what Brian wrote, the line above is wrongly placed IMHO.
You cannot know whether initialization of the OptionParser instance is
completed when still inside the block. You should rather invoke #parse
on the result of OptionParser.new.

end

puts options.inspect

Good point – but the result is the same.

Stephan

Kind regards

robert


#6

On May 23, 2009, at 21:58, Stephan W. wrote:

I don’t think that ‘-help’ should be treated the same as ‘-h -ex lp’
or
‘-h --ex lp’. In particular, ‘-help’ may be a misspelling of the
common ‘–help’ option. Am I doing something wrong? Is there a way to
avoid this?

When you use - instead of – you invoke short-option-parsing like:

$ ruby -dvrubygems -e ‘raise rescue nil’
ruby 1.8.6 (2008-08-11 patchlevel 287) [universal-darwin9.0]
Exception LoadError' at /Library/Ruby/Site/1.8/rubygems.rb:1106 - no such file to load -- rubygems/defaults/operating_system ExceptionLoadError’ at /Library/Ruby/Site/1.8/rubygems/
config_file.rb:35 - no such file to load – Win32API
Exception `RuntimeError’ at -e:1 -
$

Which is equivalent to:

ruby -d -v -r ubygems -e ‘raise rescue nil’


#7

Eric H. wrote:

On May 23, 2009, at 21:58, Stephan W. wrote:

I don’t think that ‘-help’ should be treated the same as ‘-h -ex lp’
or
‘-h --ex lp’. In particular, ‘-help’ may be a misspelling of the
common ‘–help’ option. Am I doing something wrong? Is there a way to
avoid this?

When you use - instead of – you invoke short-option-parsing like:

$ ruby -dvrubygems -e ‘raise rescue nil’
ruby 1.8.6 (2008-08-11 patchlevel 287) [universal-darwin9.0]
Exception LoadError' at /Library/Ruby/Site/1.8/rubygems.rb:1106 - no such file to load -- rubygems/defaults/operating_system ExceptionLoadError’ at /Library/Ruby/Site/1.8/rubygems/
config_file.rb:35 - no such file to load – Win32API
Exception `RuntimeError’ at -e:1 -
$

Which is equivalent to:

ruby -d -v -r ubygems -e ‘raise rescue nil’

There is some precedence for disabling this kind of command line
parsing, see

http://jargs.sourceforge.net/doc/api/jargs/gnu/CmdLineParser.NotFlagException.html

http://tinyurl.com/notflagexception

Quote:

public static class CmdLineParser.NotFlagException
extends CmdLineParser.UnknownOptionException

Thrown when the parsed commandline contains multiple concatenated
short options, such as -abcd, where one or more requires a value.
getMessage() returns an english human-readable error string.

End quote

This looks like a useful option to support.

Stephan