[libvirt] [PATCH v2 03/12] virsh: Conditionally Ignore the first entry in list of completions

[Lin Ma]

On 05/10/2018 05:17 PM, Michal Privoznik wrote:
> On 05/08/2018 04:20 PM, Lin Ma wrote:
>> The first entry in the returned array is the substitution for TEXT. It
>> causes unnecessary output if other commands or options share the same
>> prefix, e.g.
>>
>> $ virsh des<TAB><TAB>
>> des      desc     destroy
>>
>> or
>>
>> $ virsh domblklist --d<TAB><TAB>
>> --d        --details  --domain
>>
>> This patch fixes the above issue.
>>
>> Signed-off-by: Lin Ma <lma at suse.com>
>> ---
>>   tools/vsh.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/vsh.c b/tools/vsh.c
>> index 73ec007e56..57f7589b53 100644
>> --- a/tools/vsh.c
>> +++ b/tools/vsh.c
>> @@ -3458,6 +3458,7 @@ cmdComplete(vshControl *ctl, const vshCmd *cmd)
>>       const vshCmdOpt *opt = NULL;
>>       char **matches = NULL, **iter;
>>       virBuffer buf = VIR_BUFFER_INITIALIZER;
>> +    int n;
> This needs to be size_t. Even though it's not used to directly access
> entries of @matches array, it kind of is. It's used to count them. And
> int is not guaranteed to be able to address all of them.
>
>>   
>>       if (vshCommandOptStringQuiet(ctl, cmd, "string", &arg) <= 0)
>>           goto cleanup;
>> @@ -3493,8 +3494,11 @@ cmdComplete(vshControl *ctl, const vshCmd *cmd)
>>       if (!(matches = vshReadlineCompletion(arg, 0, 0)))
>>           goto cleanup;
>>   
>> -    for (iter = matches; *iter; iter++)
>> +    for (n = 0, iter = matches; *iter; iter++, n++) {
>> +        if (n == 0 && matches[1])
>> +            continue;
> This can be rewritten so that we don't need @n at all:
>
>    if (iter == matches && matches[1])
>        continue;
>
> Or even better, just start iterating not from the first but second entry:
>
>      for (iter = &matches[1]; *iter; iter++)
>          printf("%s\n", *iter);
It seems it can't handle the case that no command or option share the 
same prefix.
say 'event' command, when users type virsh ev<TAB><TAB>, there is no 
other command
sharing 'ev' prefix, in this case, the matches[1] is NULL and we need to 
print the
value in matches[0],I think we can't skip the first entry in this case.
So the code block 'if (iter == matches && matches[1])  continue;' looks 
like a better
choice.If you think so,
I'd like to write a patch to do it, Do you agree?
meanwhile, I want to remove those comment due to we can't skip first 
entry, Do you agree?

> This is safe because:
> a) @matches is guaranteed to be non-NULL at this point (due to check above),
> b) @matches is NULL terminated array and as you and documentation [1]
> say, the first entry is substitution for text (which we want to skip).
>
> So even if the array is nothing but the substitution and NULL,
> matches[1] will be NULL:
>
>    matches = { "subs", NULL };
>
> Also, I'm adding a small comment because it is not obvious why we are
> skipping the first entry.
>
> ACK then.
>
> Michal
>
> 1: http://www.delorie.com/gnu/docs/readline/rlman_46.html
>
Thanks,
Lin