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

> Good find. I'll have to bulk up the help text.

Yes.

> This raises a question: in interactive mode, should we give some feedback
> as to the result of an \if or \elif test? (see below)

Obviously \if makes more sense for scripting.

However I would say yes, it should provide some feedback... This means
probably adding a new prompt substitution "%<something>". In the worst
case, the prompt should reflect the current stack, or at least the top of
the task...

Maybe use "%?" which could be substituted by:

empty stack -> ""
ignore state -> "." or "(i)"
*_true state -> "t" or "(t)"
*_false state -> "f" or "(f)"

calvin=> \if true
calvin=(t)> \echo "running..."
running...
calvin=(t)> \else
calvin=(f)> whatever
calvin=(f)> \endif
calvin=>

>> Therefore making it possible to break out of \if-mode with Ctrl-C would be
>> an improvement, I think.
>> I would even prefer it when \q would exit psql always, even from within
>> \if-mode.
> So I don't think we can do that. At least not in non-interactive mode.

Yep.

> As for CTRL-C, I've never looked into what psql does with CTRL-C, so I
> don't know if it's possible, let alone desirable.

I think that ctrl-c should abandon current command, which is what the user
expect when things go wrong. I would suggest to pop the stack on ctrl-C on
an empty input, eg:

calvin=> \if true
calvin=(t)> SELECT
calvin-(t)> <ctrl-C>
calvin=(t)> <ctrl-C>
calvin=>

>> Also, shouldn't the prompt change inside an \if block?
>
> That's a good question. I could see us finding ways to print the t/f of
> whether a branch is active or not, but I'd like to hear from more people
> before diving into something like that.

See above.

Adding a state indicator is probably ok, the key question is whether the
default prompt is changed.

--
Fabien.