rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Thien-Thi Nguyen]

The above form lives in my Emacs init flow, causing trailing whitespace to be
deleted on `save-buffer' (C-x C-s).  For many projects (but not Guile) this
DTRT, because trailing whitespace is not tolerated.  Jim Meyering gives a
nice rationale in <http://old.nabble.com/whitespace-cleanup-td6828228.html>.

I propose Guile also not tolerate trailing whitespace.  What do people think?

thi

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Ludovic Courtès]

Hi,

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> The above form lives in my Emacs init flow, causing trailing whitespace to be
> deleted on `save-buffer' (C-x C-s).  For many projects (but not Guile) this
> DTRT, because trailing whitespace is not tolerated.  Jim Meyering gives a
> nice rationale in <http://old.nabble.com/whitespace-cleanup-td6828228.html>.
>
> I propose Guile also not tolerate trailing whitespace.  What do people think?

I agree, but adding such a hook would cause many gratuitous diffs, which
then blur VCS history (using ‘git blame’ becomes almost useless).

Instead, I’d suggest using ‘show-trailing-whitespace’.  Unfortunately,
that can’t be a per-file or per-directory local variable [0] so we can
just kindly ask people to add it to their ‘.emacs’.  :-)

What do you think?

Thanks,
Ludo’.

[0] http://debbugs.gnu.org/db/53/5312.html

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Thien-Thi Nguyen]

() ludo@gnu.org (Ludovic Courtès)
() Wed, 13 Jan 2010 11:53:01 +0100

   I agree, but adding such a hook would cause many gratuitous
   diffs, which then blur VCS history (using ‘git blame’ becomes
   almost useless).

Usually, once a project decides to use some whitespace policy,
there is a one-time change-only-whitespace commit after which
programmers are expected to adhere to the new policy (using
whatever tools they choose).  This way, the pain from gratuitous
diffs are minimized.

Another way to minimize pain is to instruct the diff program to
ignore whitespace (this means in practice `--ignore-space-change'
(-b) or `--ignore-space-at-eol' for "git diff").

Having said that, i see (count of affected lines by file below)
that even a one-time change will touch a lot of lines.  Hmmm.

   Instead, I’d suggest using ‘show-trailing-whitespace’.
   Unfortunately, that can’t be a per-file or per-directory local
   variable [0] so we can just kindly ask people to add it to
   their ‘.emacs’.  :-)

   What do you think?

I'd rather a clean break than relying on the chance that the
source will be opportunistically cleaned up going forward.

thi


____________________________________________________
$ git grep -c -H -e \[\ \	\]\$ \
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1395	gc-benchmarks/larceny/nucleic2.sch
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1	srfi/srfi-14.h
1	module/system/vm/frame.scm
1	module/system/base/compile.scm
1	module/srfi/Makefile.am
1	module/language/elisp/runtime/macro-slot.scm
1	module/language/elisp/lexer.scm
1	module/Makefile.am
1	libguile/vm.h
1	libguile/vm-i-loader.c
1	libguile/vm-expand.h
1	libguile/vectors.h
1	libguile/variable.h
1	libguile/values.c
1	libguile/strorder.c
1	libguile/srfi-13.h
1	libguile/regex-posix.c
1	libguile/quicksort.i.c
1	libguile/pthread-threads.h
1	libguile/properties.c
1	libguile/programs.h
1	libguile/numbers.h
1	libguile/null-threads.h
1	libguile/null-threads.c
1	libguile/mkstemp.c
1	libguile/lang.c
1	libguile/instructions.h
1	libguile/instructions.c
1	libguile/hooks.h
1	libguile/guile.c
1	libguile/gdb_interface.h
1	libguile/gc.h
1	libguile/gc-malloc.c
1	libguile/foreign.h
1	libguile/fluids.h
1	libguile/extensions.c
1	libguile/eval.h
1	libguile/discouraged.h
1	libguile/debug-malloc.c
1	libguile/chars.h
1	libguile/bitvectors.h
1	libguile/ChangeLog-2008
1	libguile.h
1	gc-benchmarks/larceny/run-benchmark.chez
1	gc-benchmarks/larceny/earley.sch
1	examples/scripts/simple-hello.scm
1	examples/modules/main
1	examples/modules/README
1	examples/compat/compat.h
1	examples/README
1	examples/Makefile.am
1	examples/ChangeLog-2008
1	emacs/gds-test.el
1	emacs/Makefile.am
1	doc/use-cases.fig
1	doc/tutorial/Makefile.am
1	doc/sources/unix-other.texi
1	doc/sources/jimb-org.texi
1	doc/ref/standard-library.am
1	doc/ref/mod-getopt-long.texi
1	doc/ref/misc-modules.texi
1	doc/ref/hierarchy.png
1	doc/ref/guile.texi
1	doc/ref/goops.texi
1	doc/ref/api-procedures.texi
1	doc/r5rs/Makefile.am
1	doc/example-smob/ChangeLog-2008
1	doc/ChangeLog-guile-doc
1	benchmark-suite/benchmarks/chars.bm
1	benchmark-suite/ChangeLog-2008
1	README.guile-vm
1	HACKING

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Neil Jerram]

ludo@gnu.org (Ludovic Courtès) writes:

> (using ‘git blame’ becomes almost useless).

Wouldn't `git blame -w' solve that problem?

    Neil

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Ludovic Courtès]

Hi,

Neil Jerram <neil@ossau.uklinux.net> writes:

> ludo@gnu.org (Ludovic Courtès) writes:
>
>> (using ‘git blame’ becomes almost useless).
>
> Wouldn't `git blame -w' solve that problem?

Hmm, possibly, yes (I didn’t know this option).

Thanks,
Ludo’.

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Andy Wingo]

On Wed 13 Jan 2010 10:06, Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> I propose Guile also not tolerate trailing whitespace.  What do people
> think?

To change all that code is a bit of a pain, for not very much gain. I
personally don't care about the topic.

I would be happier if my use of Emacs didn't leave me often with
trailing whitespace. But such as it is, I don't want to play manual
garbage collector for stray spaces, which have no detriment on code.

Andy
-- 
http://wingolog.org/

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Thien-Thi Nguyen]

() Andy Wingo <wingo@pobox.com>
() Wed, 13 Jan 2010 21:02:03 +0100

   I would be happier if my use of Emacs didn't leave me often with
   trailing whitespace.

See subject line.

   But such as it is, I don't want to play manual garbage
   collector for stray spaces, which have no detriment on code.

Well, if there's concensus, i'm happy to do the janitorial duties.

thi

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Ludovic Courtès]

Hi,

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> Well, if there's concensus, i'm happy to do the janitorial duties.

IMO the cons (blurring VCS history) outweighs the pros.

But please (setq show-trailing-whitespace t).

Thanks,
Ludo’.

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Neil Jerram]

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> The above form lives in my Emacs init flow, causing trailing whitespace to be
> deleted on `save-buffer' (C-x C-s).  For many projects (but not Guile) this
> DTRT, because trailing whitespace is not tolerated.  Jim Meyering gives a
> nice rationale in <http://old.nabble.com/whitespace-cleanup-td6828228.html>.

I'm afraid those rationales don't persuade me:

>>  - trailing blanks can change the semantics of your code

That's what tests are for.

>>  - these differences can lead to unnecessary merge conflicts

Hasn't been a problem in practice AFAIK.  I've been doing a lot of
merging at work recently, with a lot of real merge conflicts.  The few
that are caused by whitespace are easy to spot, and give me a pleasant
interlude between the ones that are really difficult.

>>  - some people use editors that automatically convert / +\t/
>>      sequences to just TABs (this is relevant not just for leading
>>      indentation, but also for e.g., regular expressions, where
>>      it's easy to write a e.g. "[ ]" (space-TAB) as part of a
>>      grep or sed pattern.  Of course, if you're using a modern
>>      enough tool, you can avoid the problem by using "\t".  This
>>      is why it is better to write the above as "[ ]" (TAB-space).

I can't see why this has to do with _trailing_ whitespace, and it seems
obvious to me that those editors are just broken.

>>  - some packages (coreutils :-) have a "make distcheck" rule that will
>>      fail if it finds any such offending sequence in its sources.

We don't have that.

> I propose Guile also not tolerate trailing whitespace.  What do people think?

If you are concerned that your hook is going to generate diffs that
other developers might think are spurious - I'd say don't worry about
that.  I personally won't object to that, and I don't think Andy or Ludo
would either.

If you anticipate some other practical problem, can you say more about
what it is?

Thanks,
        Neil

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Thien-Thi Nguyen]

() Neil Jerram <neil@ossau.uklinux.net>
() Thu, 21 Jan 2010 20:46:26 +0000

   > Jim Meyering gives a nice rationale in
   > <http://old.nabble.com/whitespace-cleanup-td6828228.html>.

   I'm afraid those rationales don't persuade me: [...]

Well, i respect the work Jim Meyering does and read his rationale
w/ a more general mindset.  I agree Guile is not GNU coreutils,
and have elided the "does not apply" parts, w/ the exception of:

   > [merge conflicts]

   Hasn't been a problem in practice AFAIK.  I've been doing a lot
   of merging at work recently, with a lot of real merge
   conflicts.  The few that are caused by whitespace are easy to
   spot, and give me a pleasant interlude between the ones that
   are really difficult.

If there is a whitespace policy, we can eliminate those conflicts
(by rejecting non-compliant patches).  This is good!

   If you are concerned that your hook is going to generate diffs
   that other developers might think are spurious - I'd say don't
   worry about that.  I personally won't object to that, and I
   don't think Andy or Ludo would either.

I would rather clarify the policy (either way) and then adopt it,
than go w/o policy.  If the policy (either way) is clear, i know
how to avoid introducing spurious diffs and being inconvenienced
by them from others, and can help others do the same.

   If you anticipate some other practical problem, can you say
   more about what it is?

The practical problem is that w/o policy spurious diffs come and
go, instead of being addressed once (one-shot big-commit if policy
is "deny", a blurb in HACKING to justly orient newbies if "allow").
This is "practical" in the sense of "what people will do in
practice".  It is a "problem" in the sense of "i hate burning my
geezer brain-cells on administrivia over and over and over...".

Revised proposal: Let's decide one way or the other, record the
decision (including link to this thread), and bask in the time and
effort saved by our forward thinking when the issue resurfaces w/
new programmers.

thi

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Ludovic Courtès]

Hi,

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> Revised proposal: Let's decide one way or the other,

To me it’s clear: status quo, i.e., no ‘whitespace-cleanup’ or similar
all around, but encourage people not to leave trailing whitespace.

Thanks,
Ludo’.

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Thien-Thi Nguyen]

[-- Attachment #1: Type: text/plain, Size: 320 bytes --]

() ludo@gnu.org (Ludovic Courtès)
() Sat, 23 Jan 2010 17:10:50 +0100

   To me it’s clear: status quo, i.e., no ‘whitespace-cleanup’
   or similar all around, but encourage people not to leave
   trailing whitespace.

OK, thanks for the clarification.
Please find attached a patch to HACKING.

thi



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Document-trailing-whitespace-policy.patch --]
[-- Type: text/x-diff, Size: 1377 bytes --]

From 893dfb5d11e6d2ae6ff56492741711ec368257a4 Mon Sep 17 00:00:00 2001
From: Thien-Thi Nguyen <ttn@gnuvola.org>
Date: Tue, 9 Feb 2010 14:29:36 +0100
Subject: [PATCH] Document trailing whitespace policy.

* HACKING (Coding standards): Delete trailing whitespace.
Add blurb documenting trailing whitespace policy.

Signed-off-by: Thien-Thi Nguyen <ttn@gnuvola.org>
---
 HACKING |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/HACKING b/HACKING
index ffe04a8..7463fe5 100644
--- a/HACKING
+++ b/HACKING
@@ -230,7 +230,7 @@ When deprecating a definition, always follow this procedure:
 
 - Write commit messages for functions written in C using the
 functions' C names, and write entries for functions written in Scheme
-using the functions' Scheme names.  For example, 
+using the functions' Scheme names.  For example,
 
   * foo.c: Moved scm_procedure_documentation from eval.c.
 
@@ -278,6 +278,9 @@ the list of years in the copyright notice at the top of the file.
 - When you get bug reports or patches from people, be sure to list
 them in THANKS.
 
+- Do not introduce trailing whitespace (and feel free to clean it up
+opportunistically, that is, if doing so is part of some other change).
+The goal is to reduce (and over time, eliminate) spurious diffs.
 
 Naming conventions =================================================
 
-- 
1.6.3.2

Re: rfc: (add-hook 'before-save-hook 'delete-trailing-whitespace)

[Ludovic Courtès]

Hi,

Thien-Thi Nguyen <ttn@gnuvola.org> writes:

> () ludo@gnu.org (Ludovic Courtès)
> () Sat, 23 Jan 2010 17:10:50 +0100
>
>    To me it’s clear: status quo, i.e., no ‘whitespace-cleanup’
>    or similar all around, but encourage people not to leave
>    trailing whitespace.
>
> OK, thanks for the clarification.
> Please find attached a patch to HACKING.

Committed, thanks.

Ludo’.