Re: [PATCH] [WIP] org-agenda.el: Make org-entries-lessp more efficient

[Adam Spiers <orgmode@adamspiers.org>]

On Sat, Oct 24, 2020 at 01:36:05PM +0200, Bastien wrote: 
>Hi Adam, 
>
>this looks good to me, thanks a lot. 

Thanks for the review :-) 

>Does "WIP" means that you want to wait for other patches to complete 
>this one or shall I apply this one already? 

The intention is for it to be a standalone patch, so I don't think 
there's any need to wait for other patches.  The "WIP" was coming more 
from the fact that I haven't done extensive testing to make sure I 
didn't break a single one of the many sorting criteria - especially 
this one:

+    ('category-keep   (if (org-cmp-category a b) +1 nil)) ;; FIXME: check this

Ideally there would already be unit and/or functional tests covering 
agenda sorting, but I can't see any and I imagine they would be 
non-trivial to add (although perhaps not too difficult either). 

Also, the previous behaviour was to silently ignore 
user-defined-{up,down} if org-agenda-cmp-user-defined was not defined, 
but that intuitively felt wrong to me (IMHO it kind of violates the 
Principle of Least Surprise) so I didn't bother to preserve that 
behaviour.  However I admit that is a pretty subjective choice, so if 
you think the existing behaviour should be preserved, I can tweak the 
code to do that.  In fact, even if you agree with me that it would be 
better to generate an error when user-defined-{up,down} is used with 
org-agenda-cmp-user-defined being nil, I just noticed that it currently 
generates the very unhelpful error: 

     org-entries-cmp-1: Symbol’s function definition is void: nil

so we would want to explicitly catch that case and generate a more 
helpful error message, e.g. "org-agenda-sorting-strategy contains 
user-defined sorting but org-agenda-cmp-user-defined is nil". 

BTW, as you can partially see from the below link, I did some 
performance profiling relating to this change and it did indeed seem 
to shave a few milliseconds off org-entries-lessp, although in the 
grand scheme of things, that didn't make as much of a dent in 
org-agenda's running time as I'd hoped for ;-) 

     https://gist.github.com/trishume/40bf7045a23412d4c016f5e8533437db#gistcomment-3494087