From: Tom Lane <tgl@sss.pgh.pa.us>
To: Christoph Berg <myon@debian.org>
cc: Andres Freund <andres@anarazel.de>, Amit Kapila <amit.kapila16@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: pgsql: Add basic TAP tests for psql's tab-completion logic.
In-reply-to: <19973.1578351988@sss.pgh.pa.us>
References: <E1in6ft-0004zR-6l@gemulon.postgresql.org>
 <20200103110128.GA28967@msg.df7cb.de> <13708.1578059577@sss.pgh.pa.us>
 <25771.1578249042@sss.pgh.pa.us> <20200106105608.GB18560@msg.df7cb.de>
 <3764.1578323719@sss.pgh.pa.us> <20200106191303.GA3975@msg.df7cb.de>
 <19973.1578351988@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Mon, 06 Jan 2020 18:06:28 -0500"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <28772.1578436137.1@sss.pgh.pa.us>
Date: Tue, 07 Jan 2020 17:28:57 -0500
Message-ID: <28773.1578436137@sss.pgh.pa.us>
Precedence: bulk

I wrote:
> I installed libedit_3.1-20150325.orig.tar.gz from source here, and it
> passes our current regression test and seems to behave just fine in
> light manual testing.  (I did not apply any of the Debian-specific
> patches at [1], but they don't look like they'd explain much.)
> So I'm a bit at a loss as to what's going wrong for you.  Is the test
> environment for Xenial the same as for the other branches?

To dig deeper, I set up an actual installation of xenial, and on that
I can replicate the tab-completion misbehavior you reported.  The cause
appears to be that libedit's rl_line_buffer does not contain the current
line as expected, but the previous line (or, initially, an empty string).
Thus, the hack I put in to make things pass on current libedit actually
makes things worse on this version --- although it doesn't fully pass
even if I revert ddd87d564, since there are other places where we
depend on rl_line_buffer to be valid.

So that raises the question: why does xenial's version of libedit
not match either its documentation or the distributed source code?
Because it doesn't.

			regards, tom lane