Re: master 695f679: Remove ; ; ; ###tramp-autoload cookie from Tramp defcustoms (Bug#47063)

[Lars Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> What's the performance impact here?  This is going to be called a whole
>> bunch of times when the user hits TAB...
>
> It should be OK to do the condition-case wrapping around the loop rather
> than within it, so the performance impact should be negligible.

Yup; if it's hoisted out of the loop, there'd be no performance impact,
but it would make it less useful, though -- as with erroring out, you'd
get no completion.  With it in the loop, you'd just ignore the specific
predicate that fails, I think?

>> I'm also not quite sure why we should be ignoring these errors --
>> they're code errors, like any others, and shouldn't be expected to
>> fail, should they?
>
> The purpose is to make sure people can still `M-x` even in the presence
> of such errors.  They *should* never happen, but an error there shouldn't
> render Emacs unusable ;-)

I'm all for adding resiliency to central parts of Emacs, so it's good in
that sense.  But we don't, in general, ignore coding errors like this, I
think?  For instance, if there's an error when loading an .el file, we
bug out -- we don't catch it and carry on.

So I don't oppose catching errors here, really -- I'm just wondering why
we're designing for allowing broken code in this particular
circumstance.  Do we expect these code snippets to break for some
reason?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no