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

On Wed, Feb 22, 2017 at 6:15 PM, Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
wrote:

> On Wed, Feb 22, 2017 at 5:59 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>> Ah, I see why *that* wants to know about it ... I think. I suppose you're
>> arguing that variable expansion shouldn't be able to insert, say, an \else
>> in a non-active branch? Maybe, but if it can insert an \else in an active
>> branch, then why not non-active too? Seems a bit inconsistent.
>>
>
> The major reason was avoiding situations like what Daniel showed: where
> value of a variable that is meaningless/undefined in the current
> false-block context gets expanded anyway, and thus code inside a false
> block has effects outside of that block. Granted, his example was
> contrived. I'm open to removing that feature and seeing what breaks in the
> test cases.
>

Welcome to v15, highlights:
- all conditional data structure management moved to conditional.h and
conditional.c
- conditional state lives in mainloop.c and is passed to
HandleSlashCommands, exec_command and get_prompt as needed
- no more pset.active_branch, uses conditional_active(conditional_stack)
instead
- PsqlScanState no longer has branching state
- Implements the %R '@' prompt on false branches.
- Variable expansion is never suppressed even in false blocks, regression
test edited to reflect this.
- ConditionalStack could morph into PsqlFileState without too much work.