Re: libedit history seems to be misbehaving / broken

Tomas Vondra <tomas@vondra.me> writes:
> I'm not terribly familiar with libedit, so can't say if it's a bug in
> libedit, or if we're just using it wrong in some way. I investigated
> that while on a flight from pgconf.eu, but can't look into this further.
> So let me at least share the behavior I observed, and what I found.
> Note: All of this is with libedit-3.1-53.20240808cvs.fc40.x86_64, which
> is what I currently get in Fedora 40.

libedit has been a hot mess for a long time.  psql's input.c has
workarounds for assorted bugs that it has or had in prior versions,
and what I suspect is that latest libedit has a different set of bugs.

FWIW, I don't observe any particular misbehavior with the very ancient
libedit that macOS ships.  On Fedora 39, I notice something related to
what you say: it seems like the "\q" ending a session gets repeated
into .psql_history by the next session.  I'm surprised that it's not
exactly the same as your results though, because it seems to be the
same source version:

$ rpm -q libedit
libedit-3.1-53.20240808cvs.fc39.x86_64

Didn't try the too-many-lines behavior, but it looks like that
is implemented totally by history_truncate_file(), so if that's
busted it's surely their fault.

            regards, tom lane