Re: [libvirt] [PATCH] virsh: add custom readline generator

On 27.06.2011 21:39, Eric Blake wrote: > On 06/27/2011 12:06 PM, Michal Privoznik wrote: >>> That is, if you have command-based custom generators, then each command >>> has to repeat parsing functionality, then call back to common list >>> generators; whereas if you have option-based custom generators, then you >>> have fewer callbacks because all the smarts are tied to well-typed >>> options, and after all, it is the type of each option that determines >>> which list to generate, more than the type of the command that includes >>> the option. >>> >> I was thinking about same feature and started to work on it during this >> weekend. But I ran into a problem. Basically, what I intended to >> implement, is: >> >> 1.) expand struct vshCmdDef for a char *(*callback) (const char *text, >> int state). But for real benefit, we need connection object, so we could >> e.g. list only inactive networks for 'net-start' command. And this is >> the problem, because we would have to make this object global (since >> readline functions does not allow passing any opaque value). > > As gross as it is, a global object isn't entirely bad - virsh is > single-threaded. And even if we want to make virsh threaded at some > point, I still think we can get away with adding a thread-local access > scheme. > >> >> 2.) expand each command definition with its own completer. So e.g. for >> start commands we could only list inactive domains, networks, pools, >> whatever. For destroy only active objects. And so on. > > So maybe we want both - an option-based completer that generates the > initial list, and a command-based completer that can then prune out > irrelevant options? > Well, I would say that is the highest goal to be achieved. Although that implies parsing during options generation. But I don't think I get it. Option-based completer generates list for given option, command-based completer generates list for given command (entries from this list are options). Take detach-interface for instance. This have some options: --mac: here we want option-based completer to list mac addresses of a NICs of a domain specified by --domain: since this could be left out we want here command-base completer to either list all domains, or list only those domains which have a NIC. So then we get: # detach-interface <TAB><TAB> --mac --persistent domain1 domain2 # detach-interface domain1 --mac <TAB><TAB> 00:11:22:33:44:55 01:23:45:67:89 My point is - I can't see any pruning here. But maybe I've chosen wrong example. However, this example shows we need both types of completer. Michal