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From: Dmitry Kurochkin <dmitry.kurochkin@gmail.com>
To: Daniel Schoepe <daniel@schoepe.org>, notmuch@notmuchmail.org
Subject: Re: [PATCH v2] emacs: Pass a copy to
	notmuch-saved-search-sort-function
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Date: Mon, 05 Mar 2012 19:42:12 +0400
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On Mon, 05 Mar 2012 12:17:43 +0100, Daniel Schoepe <daniel@schoepe.org> wrote:
> On Mon, 05 Mar 2012 06:21:52 +0400, Dmitry Kurochkin <dmitry.kurochkin@gmail.com> wrote:
> > On Thu,  1 Mar 2012 21:24:38 +0100, Daniel Schoepe <daniel@schoepe.org> wrote:
> > > notmuch-saved-search-sort-function might destructively modify its
> > > input (`sort' does that, for instance), so it should not be given
> > > notmuch-saved-searches directly.
> > > ---
> > 
> > -1
> > 
> > I think we should require `notmuch-saved-search-sort-function' not to
> > have side effects.  Current documentation should be more clear about
> > this.  We need to fix `notmuch-sort-saved-searches' to copy the list
> > before calling `sort'.  But we should not do it in
> > `notmuch-hello-insert-saved-searches' for any sorting function (which
> > may not need this copying).
> 
> My reasoning was that since sort is such a common function, many users
> will probably use sort for their own sorting functions, not realizing
> that it has side effects. This will lead to confusing behavior that's
> not so easy to track down.
> 
> Copying the list of saved searches when running notmuch-hello does not
> seem be relevant to performance to me, since it's a) not called that
> often and b) the list of saved searches will rarely exceed 30 elements.
> 
> Hence, this way we can avoid some headaches for users who define their
> own sorting functions at a negligible (performance) cost. Incidentally,
> this is also how notmuch-hello did it before the user-defined sections
> patches.
> 

I do not buy the argument that we should help users who implement their
own sorting functions but do not read documentation for functions they
use.  Apparently, those who implemented the `sort' function had similar
ideas.  And I do not think it is our job to add workarounds for it.

An alternative (and IMO better) solution would be to allow customization
of compare function used for sorting instead of the sorting function
itself.

Regards,
  Dmitry

> Cheers,
> Daniel