Re: [HACKERS] Time to change pg_regress diffs to unified by default?

From: David Fetter <david(at)fetter(dot)org>
To: Christoph Berg <myon(at)debian(dot)org>, Noah Misch <noah(at)leadboat(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Time to change pg_regress diffs to unified by default?
Date: 2018-11-25 23:32:30
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On Thu, Nov 22, 2018 at 02:10:59PM +0100, Christoph Berg wrote:
> Re: Noah Misch 2017-04-07 <20170407021431(dot)GB2658646(at)tornado(dot)leadboat(dot)com>
> > > > I personally, and I know of a bunch of other regular contributors, find
> > > > context diffs very hard to read. Besides general dislike, for things
> > > > like regression test output context diffs are just not well suited.
> > >
> > > Personally, I disagree completely. Unified diffs are utterly unreadable
> > > for anything beyond trivial cases of small well-separated changes.
> > >
> > > It's possible that regression failure diffs will usually fall into that
> > > category, but I'm not convinced.
> >
> > For reading patches, I frequently use both formats. Overall, I perhaps read
> > unified 3/4 of the time and context 1/4 of the time.
> >
> > For regression diffs, I use PG_REGRESS_DIFF_OPTS=-u and have never converted a
> > regression diff to context form. Hence, +1 for the proposed change.
> I've just had another case of horrible context diff from pg_regress.
> I'd claim that regression diffs are particularly bad for context diffs
> because one error will often trigger a whole chain of failures, which
> will essentially make the whole file appear twice in the output,
> whereas unified diffs would just put the original output and the error
> right next to each other at the top. Having to scroll through a whole
> .out file just to find "create extension; file not found" is very
> inefficient.
> It's nice that PG_REGRESS_DIFF_OPTS exists, but the diffs are often
> coming from automated build logs where setting the variable after the
> fact doesn't help.
> Please consider the attached patch, extension packagers will thank
> you.
> Christoph

+1 for pushing this. Regression diffs can get pretty noisy even with
it in place.

David Fetter <david(at)fetter(dot)org>
Phone: +1 415 235 3778

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