This is supposed to go on the top of:

https://www.redhat.com/archives/libvir-list/2017-October/msg01367.html

Before digging any deeper to this hole I want to make sure that
this approach is acceptable.

So how does this work. The idea is to have handful of generic
functions that fetch names (so called completers). Basically, one
completer per each libvirt object. The returned names are then
matched against (partial) user input and only matching strings
are then offered to the user. Moreover, among having .completer
each option has .completer_flags which can refine the completer's
behaviour.

For instance, in 2/2 I'm introducing virshDomainNameCompleter()
which does nothing more than virConnectListAllDomains(). However,
since it doesn't make much sense to start already running domain,
for the 'start' command .completer_flags is set to
VIR_CONNECT_LIST_DOMAINS_INACTIVE so that only inactive domains
are returned in the list.


What is missing?
What is implemented here are vshCmdOptDef completers. The general
vshCmdDef completers are still missing. Therefore:

virsh # start --domain<TAB><TAB>

works and lists inactive domains, but:

virsh # start<TAB><TAB>

doesn't (well, apart from offering options for the 'start'
command). While that would be certainly nice feature to have,
it'd require more work, because some arguments are "implicit"
based on position. For instance:

virsh # attach-interface fedora network default

which is equivalent to:

virsh # attach-interface --domain fedora --type network --source default


Also, bash autocompletion is missing. The idea there is to have
an unlisted virsh command that the bash script can call in order
to fetch list of options. But again, no movement in that area
yet.

Michal Privoznik (2):
  vsh: Call vshCmdOptDef.completer properly
  virsh: Introduce virshDomainNameCompleter

 tools/virsh-domain-monitor.c |  30 +++----
 tools/virsh-domain.c         | 182 ++++++++++++++++++++++---------------------
 tools/virsh-snapshot.c       |  24 +++---
 tools/virsh.c                |  43 ++++++++++
 tools/virsh.h                |   8 +-
 tools/vsh.c                  |  45 ++++++-----
 6 files changed, 194 insertions(+), 138 deletions(-)

-- 
2.13.6

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On Tue, Oct 31, 2017 at 14:10:25 +0100, Michal Privoznik wrote:
> This is supposed to go on the top of:
> 
> https://www.redhat.com/archives/libvir-list/2017-October/msg01367.html
> 
> Before digging any deeper to this hole I want to make sure that
> this approach is acceptable.
> 
> So how does this work. The idea is to have handful of generic
> functions that fetch names (so called completers). Basically, one
> completer per each libvirt object. The returned names are then
> matched against (partial) user input and only matching strings
> are then offered to the user. Moreover, among having .completer
> each option has .completer_flags which can refine the completer's
> behaviour.
> 
> For instance, in 2/2 I'm introducing virshDomainNameCompleter()
> which does nothing more than virConnectListAllDomains(). However,
> since it doesn't make much sense to start already running domain,
> for the 'start' command .completer_flags is set to
> VIR_CONNECT_LIST_DOMAINS_INACTIVE so that only inactive domains
> are returned in the list.
> 
> 
> What is missing?
> What is implemented here are vshCmdOptDef completers. The general
> vshCmdDef completers are still missing. Therefore:
> 
> virsh # start --domain<TAB><TAB>
> 
> works and lists inactive domains, but:
> 
> virsh # start<TAB><TAB>
> 
> doesn't (well, apart from offering options for the 'start'
> command). While that would be certainly nice feature to have,
> it'd require more work, because some arguments are "implicit"
> based on position. For instance:
> 
> virsh # attach-interface fedora network default
> 
> which is equivalent to:
> 
> virsh # attach-interface --domain fedora --type network --source default
> 
> 
> Also, bash autocompletion is missing. The idea there is to have
> an unlisted virsh command that the bash script can call in order
> to fetch list of options. But again, no movement in that area
> yet.

I think we need a way to determine whether the autocompletion is
possible without any user input. For bash autocompletion you will invoke
virsh to get any other params, but that means that for connections
requiring authentication you'd get stuck waiting for input (or openning
an ssh connection) which may throw off users.

This might happen too often on RHEV boxes since they use polkit auth.

It might be possible to work around polkit by connecting without auth
callbacks, but for qemu+ssh you don't really have options IMO.

Maybe you'll need to specifically disable it on ssh connections using
the default transport.

For libssh and libssh2 you can allow that but it's rather expensive to
instantiate the connection just to query a list of VMs after you press
tab.

Peter
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On 10/31/2017 02:43 PM, Peter Krempa wrote:
> On Tue, Oct 31, 2017 at 14:10:25 +0100, Michal Privoznik wrote:
>> This is supposed to go on the top of:
>>
>> https://www.redhat.com/archives/libvir-list/2017-October/msg01367.html
>>
>> Before digging any deeper to this hole I want to make sure that
>> this approach is acceptable.
>>
>> So how does this work. The idea is to have handful of generic
>> functions that fetch names (so called completers). Basically, one
>> completer per each libvirt object. The returned names are then
>> matched against (partial) user input and only matching strings
>> are then offered to the user. Moreover, among having .completer
>> each option has .completer_flags which can refine the completer's
>> behaviour.
>>
>> For instance, in 2/2 I'm introducing virshDomainNameCompleter()
>> which does nothing more than virConnectListAllDomains(). However,
>> since it doesn't make much sense to start already running domain,
>> for the 'start' command .completer_flags is set to
>> VIR_CONNECT_LIST_DOMAINS_INACTIVE so that only inactive domains
>> are returned in the list.
>>
>>
>> What is missing?
>> What is implemented here are vshCmdOptDef completers. The general
>> vshCmdDef completers are still missing. Therefore:
>>
>> virsh # start --domain<TAB><TAB>
>>
>> works and lists inactive domains, but:
>>
>> virsh # start<TAB><TAB>
>>
>> doesn't (well, apart from offering options for the 'start'
>> command). While that would be certainly nice feature to have,
>> it'd require more work, because some arguments are "implicit"
>> based on position. For instance:
>>
>> virsh # attach-interface fedora network default
>>
>> which is equivalent to:
>>
>> virsh # attach-interface --domain fedora --type network --source default
>>
>>
>> Also, bash autocompletion is missing. The idea there is to have
>> an unlisted virsh command that the bash script can call in order
>> to fetch list of options. But again, no movement in that area
>> yet.
> 
> I think we need a way to determine whether the autocompletion is
> possible without any user input. For bash autocompletion you will invoke
> virsh to get any other params, but that means that for connections
> requiring authentication you'd get stuck waiting for input (or openning
> an ssh connection) which may throw off users.

Right. I haven't encountered this problem in my local (read limited)
testing. For interactive virsh instead of calling
virshConnectionHandler() I can check for:

if (!priv->conn || virConnectIsAlive(priv->conn) != 0)
    return NULL;

This means that you'd get autocompletion only if you're connected and
your connection is valid. For bash we'd be opening autocompletion for
each run which would indeed be too expensive. On the other hand, isn't
that how every other tool does that? For instance, firewall-cmd must
connect to the daemon to fetch list of zones/rules/...  On the other
hand, that connection is only local (through some UNIX socket I assume).

Long story short, we might allow autocompletion in bash only for local
connections.

Michal

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