Re: [Monotone-devel] New commands (for mtn, in lua)

[William Uther]

On 04/09/2007, at 7:29 AM, Matthew Sackman wrote:

> On Fri, Jul 06, 2007 at 10:17:22AM -0700, William Uther wrote:
> > On 06/07/2007, at 9:00 AM, address@hidden wrote:
> > > On Friday 06 July 2007, William Uther wrote:
> > > >    mtn_automate(...) : This allows any of the automate commands  
> > > > to be
> > > > called from lua.  The result is returned as a string.
> > >
> > > Seems like something one really wants to have.
> > >
> > > However, there is potential for deadlocks, when some command  
> > > calls a Lua
> > > hook
> > > that calls an automate command that calls a Lua hook...
> >
> > I didn't want lua hooks calling automate commands because I wasn't  
> > sure
> > what that would do, and I didn't
> > think it was necessary.  So there is a flag in the code that only  
> > turns
> > mtn_automate on when it is being
> > called from a user command.  It also turns the flag off inside  
> > mtn_automate
> > itself so you can't get
> > recursion (you'll get an error if you try).
>
> Agh. I'm still running 0.36, so do tell if this has been changed, but
> looking at the code, it hasn't.
>
> This is a major pain for me. I would like to be able to write hooks
> that, eg on note_netsync_revision_received, take the revision and can
> get hold of parents, or do diffs. This flag would seem to prevent me
> from doing that.
>
> Now at this point I don't mind if you want to prohibit any automate
> command that can modify the mtn database and just want to allow pure
> functions, that would suit me fine. But err, it would be great to get
> this functionality to work.

There is a lot to test there.  If you want to try it, you could  
search the code for "mtn_automate_allowed".  It is the boolean flag  
that switches the mtn_automate lua
function on and off.  The definition of the mtn_automate lua function  
is in cmd_automate.cc; look for LUAEXT(mtn_automate, ).  There is a  
check there:

      E(app_p->mtn_automate_allowed,
          F("It is illegal to call the mtn_automate() lua extension,\n"
            "unless from a command function defined by  
register_command()."));

If you comment out that check, then you can test for yourself what  
works and what doesn't.

As I said, the reason I put that check in was that I wasn't sure that  
it would work, not because I was sure that it wouldn't.

Be well,

Will        :-}