[PATCH stable] revset: don't cache abstractsmartset min/max invocations infinitely

[Yuya Nishihara]

On Wed, 26 Oct 2016 14:09:17 +0200, Mads Kiilerich wrote:
> On 10/26/2016 01:21 PM, Yuya Nishihara wrote:
> > On Tue, 25 Oct 2016 18:57:26 +0200, Mads Kiilerich wrote:
> >> # HG changeset patch
> >> # User Mads Kiilerich <madski at unity3d.com>
> >> # Date 1477414587 -7200
> >> #      Tue Oct 25 18:56:27 2016 +0200
> >> # Branch stable
> >> # Node ID c2fe58cd4235fc6c8cabea882794303d620bec3a
> >> # Parent  76c57e1fe79b0980b377b4f305635dea393d6315
> >> revset: don't cache abstractsmartset min/max invocations infinitely
> >>
> >> There was a "leak", apparently introduced in ab66c1dee405. When running:
> >>
> >>      hg = hglib.open('repo')
> >>      while True:
> >>          hg.log("max(branch('default'))")
> >>
> >> all filteredset instances from branch() would be cached indefinitely by the
> >> @util.cachefunc annotation on the max() implementation.
> > Indeed. We've cached {self: v} pair every time max() was called.
> > Queued this for stable, thanks.
> >
> >> -    @util.cachefunc
> >>       def min(self):
> >>           """return the minimum element in the set"""
> >> -        if self.fastasc is not None:
> >> -            for r in self.fastasc():
> >> -                return r
> >> -            raise ValueError('arg is an empty sequence')
> >> -        return min(self)
> >> -
> >> -    @util.cachefunc
> >> +        if self.fastasc is None:
> >> +            v = min(self)
> >> +        else:
> >> +            for v in self.fastasc():
> >> +                break
> >> +            else:
> >> +                raise ValueError('arg is an empty sequence')
> >> +        self.min = lambda: v
> >> +        return v
> > I slightly prefer using propertycache() and wrap it by a function, which
> > is a common pattern seen in context.py, but that's just a nitpicking.
> 
> Exactly what do you mean with wrapping the property by a function? I 
> don't see a clear pattern of that in context.py?

Yes. What I have in mind is parents() -> self._parents for instance.

> Instead, I would perhaps prefer to introduce a 'gettercache' that works 
> on methods that only have self as parameter (and thus can set a simple 
> instance method as I do here)  ... or a 'methodcache' that would be like 
> cachefunc but store the cache on the first 'self' parameter.

That also seems fine. (I'm not a big fan of overwriting methods since we're
likely to create self->self cycle, but that wouldn't be the case here.)