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

Hello Tom,

>>> I also fear that there are corner cases where the behavior would still
>>> be inconsistent. Consider
>>>
>>> \if ...
>>> \set foo `echo \endif should not appear here`
>
>> In this instance, ISTM that there is no problem. On "\if true", set is
>> executed, all is well. On "\if false", the whole line would be skipped
>> because the if-related commands are only expected on their own line, all
>> is well again. No problem.
>
> AFAICS, you misunderstood the example completely, or else you're proposing
> syntax restrictions that are even more bizarre and unintelligible than
> I thought before.

Hmmm. The example you put forward does work as expected with the rule I
suggested. It does not prove that the rules are good or sane, I'm just
stating that the example would work consistently.

> We cannot have a situation where the syntax rules for backslash commands
> inside an \if are fundamentally different from what they are elsewhere;

Indeed, I do not see an issue with requiring some new backslash commands
to be on their own line: Any average programmer would put them like that
anyway for readability. What is the point of trying to write code to
handle strange unmaintainable oneliners?

> that's just going to lead to confusion and bug reports.

Whatever is done, there will be some confusion and bug reports:-)

If someone writes a strange one-liner and see that it generates errors,
then the error messages should be clear enough. Maybe they will complain
and fill in bugs because they like backslash-command oneliners. That is
life.

Now you are the committer and Corey is the developer. I'm just a reviewer
trying to help. I can still review a larger patch which tries to be subtly
compatible with a lack of previous clear design by adding code complexity,
even if I think that this particular effort is a bad idea (i.e. mis-spent
resource on a useless sub-feature which makes future maintenance harder).
With some luck, Corey may find a way of doing it which is not too bad.

--
Fabien.