Re: [Monotone-devel] Hooks...

[Matthew Sackman]

On Wed, Sep 05, 2007 at 03:19:02PM +0200, Richard Levitte wrote:
> In message <address@hidden> on Wed, 5 Sep 2007 13:54:23 +0100, Matthew 
> Sackman <address@hidden> said:
> matthew> Each hook can return one of three values: everything ok;
> matthew> non-fatal error; fatal error.
> 
> Good.  We need to decide how that should work, because nil doesn't
> necessarely imply an error (let alone that it doesn't describe the
> fatality of an error).

Right, so if it was Haskell and not lua then it'd be
(a, ErrorStatus) where a is polymorphic in the type of the
result of the hook. I suggest something similar - a tuple where one
indicates the result of the hook (or nil if no result) and the other
indicates the error.

But this opens up a large pot of worms. If the hook is some sort of
"does x have permission to do y" then when do you stop? Is it a
conjunction or disjunction of results? Or is it a 3-valued logic and you
just go through the list of hooks until you find a definitive
True/False? In which case, what happens if all functions return "meh"?

Bother. Maybe this should only be permitted on hooks that don't return a
result. It makes in rather easier... simplest thing first and all that?

> matthew> > - Do we want a third function that returns information
> matthew> >   about a hook, such as how many functions are attached and
> matthew> >   their identities (the id returned by add_hook()), and
> matthew> >   whatever other data there may be.
> matthew> 
> matthew> How do imagine this to be used? I don't see the value of it
> matthew> from the hook's perspective, and whilst it could be valueable
> matthew> to a user, if the user doesn't know what hooks they have
> matthew> registered then they have other problems.
> 
> Right, and all users are always aware of what is in /etc/monotonerc...

Well quite.

Matthew