Lazily registering hooks?

[Jelmer Vernooij]

On Mon, 2010-05-31 at 07:59 +1200, Robert Collins wrote:
> A couple of things - we already have a registry of hooks, so there
> isn't a  big conceptual change there, but I would be sad to see the
> details of hooks centralised - if feels bad.
> 
> Another thing we could do is supply a hook to trigger that calls back
> when some hook point becomes available.
> 
> You wouldn't bother with it for most things: effectively all
> operations need Tree, Branch, Repository, Lock, Command etc. But to
> lazy handle info and rio:
> 
> def hook_when_used(modulename, attrname, hooks):
>     """Called when a hooks object becomes available.
> 
>     :param modulename: The module the hooks are defined in. e.g. bzrlib.smart
>     :param attrname: The attribute within the module. e.g. SmartTCPServer.hooks
>     :param hooks: The hooks object itself
>     """
>     if (modulename, attrname) == ('bzrlib.msgeditor', 'hooks'):
>         hooks.install_named_hook(....)
>     elif ...
> 
> 
> And finally, when using this api, you'd get called immediately for
> already-present hooks, so you wouldn't need to care about what order
> things happen in.
The major disadvantage of that approach though is that that means every
single plugin needs more plumbing to deal with hook registration. 

Cheers,

Jelmer