[libvirt] [PATCHv3 2/6] virsh: Add vshCmdCompleter and vshOptCompleter

[Eric Blake]

[re-adding the list, which was accidentally omitted]

On 08/28/2013 05:26 AM, Tomas Meszaros wrote:
>> Per-option completions make sense.  For example, 'virsh vol-key --pool
>> <TAB>' wants to use a pool completer, while 'virsh vol-key --vol <TAB>'
>> wants to use a volume completer; furthermore, 'virsh vol-key <TAB>'
>> should be the combination of the option completer (showing --vol and
>> --pool) AND the volume completer filtered to names not starting with '-'
>> (since virsh has the semantics that arguments are positional, where the
>> option '--vol' is implied if the argument that appears in that position
>> does not resemble an option).
> 
> So If I get it right, you are suggesting that it should work like this:
> 
> virsh # vol-key <TAB>
> vol1	vol2	pool1	pool2
> 
> as you said, combination of --vol and --pool completers.

No, it should work like this:

virsh# vol-key <TAB>
vol1 vol2 --vol --pool

the combination of all (non-option) completions for the current
available mandatory option (volume completer), and of all possible
options that still make sense at this point in the command line.

Likewise:

virsh# vol-key vol <TAB>
pool1 pool2 --pool

virsh# vol-key -<TAB>
--vol --pool

virsh# vol-key v<TAB>
vol1 vol2

virsh# vol-key --pool <TAB>
pool1 pool2

virsh# vol-key --pool pool1 <TAB>
vol1 vol2 --vol

and so forth.

> 
> 
> I was initially thinking that completion should work like this:
> 
> virsh # vol-key <TAB>
> vol1	vol2
> 
> It is completing <vol> first becasue <vol> is only mandatory argument
> for this command.

It is a mandatory option, but mandatory options need not come first.
Remember, our option parser allows mandatory options to occur
positionally without an option name, OR to be interleaved in any other
order by including the option string.

> 
> 
> Only if someone type:
> 
> virsh # vol-key --pool <TAB>
> pool1	pool2
> 
> then call --pool completer.

This is correct - once an option is awaiting an argument, then the
option completer must return nothing at that point in time.  But if you
look at it as the union of two completers - the set of options that are
still valid in the current context, and the set of strings that are
valid assuming positional semantics of the current option, you will
always get the right answer, without needing a per-command completer
(just per-option completers).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org



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