Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless)

On Fri, Mar 3, 2017 at 3:18 AM, Fabien COELHO <coelho@cri.ensmp.fr> wrote:
> I'm ok with this patch. I think that the very simple automaton code
> structure achieved is worth the very few code duplications. It is also
> significantly shorter than the nested if/switch variants, and it does
> exactly what Tom and Robert wished with respect to errors, so I think that
> this is a good compromise.

I think that I have not taken a firm position on what the behavior
should be with respect to errors.    I took the position that the
messages being printed saying what happened were too detailed, because
they not only described what had happened but also tried to
prognosticate what would happen next, which was dissimilar to what we
do elsewhere and likely to be hard to maintain - or even get right for
v1.  But I have not taken a position on what should happen if the
condition for \if or \elsif evaluates to a baffling value.  Corey's
prior proposal was to treat it, essentially, as neither true nor
false, skipping both arms of the if.  Tom seems to want an invalid
value treated as false.  You could also imagine pretending that the
command never happened at all, likely leading to complete chaos.
Other positions are also possible.  I suggest that doing it the way
Tom likes may be the path of least resistance, but this isn't really
something I'm very animated about personally.

-- 
Robert Haas
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