Preserving trailing spaces

Preserving trailing spaces

[jgombos]

I know it's a strange request to want to preserve trailing spaces; most folks
want to nuke them.  I'm working on a project where trailing spaces actually
have meaning (it's how the developer prevents the automated semantecize tool
from concatenating a long line of code that's intended to span multiple
lines for readability).

They have (probably inadvertently) installed Apex Emacs (aka aemacs), which
is essentially plain old emacs 20.7.1 with Rational's Apex functionality
integrated into the menu.  I'm glad they provided it, but I'm the only emacs
user on the team, as everyone else is using the Rational's proprietary and
very basic editor.

So to get to the issue, emacs wipes out the trailing whitespace on every
file I make a change to, and the semantizer rearranges code that I didn't
touch, adding substantial noise to the diffs - which could frustrate
reviewers.  How do I prevent emacs from nuking the trailing whitespace?  

Everything I've read indicates that emacs automatically preserves
whitespace, and that it must be proactively configured to delete trailing
whitespace.  My .emacs file is clean.  So somewhere in this aemacs
installation, there must be a hook or something that I need to override. 
How would I discover where that's happening?  Is it the lisp code for
Ada-mode?
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Re: Preserving trailing spaces

[Dieter Wilhelm]

jgombos <nabble.forum.jog@spamgourmet.com> writes:

> Everything I've read indicates that emacs automatically preserves
> whitespace, and that it must be proactively configured to delete trailing
> whitespace.  My .emacs file is clean.  So somewhere in this aemacs
> installation, there must be a hook or something that I need to override. 
> How would I discover where that's happening?  Is it the lisp code for
> Ada-mode?

I've seen in ada-mode.el.gz (Emacs 22.0.95, in /lisp/progmodes) a
variable which seem to control this, please try:

(setq ada-clean-buffer-before-saving nil)

-- 
    Best wishes

    H. Dieter Wilhelm
    Darmstadt, Germany

Re: Preserving trailing spaces

[jgombos]

Dieter Wilhelm wrote:
> 
> (setq ada-clean-buffer-before-saving nil)
> 
Yes!  That was it!  

Thank you!
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Re: Preserving trailing spaces

[Giorgos Keramidas]

jgombos <nabble.forum.jog@spamgourmet.com> writes:
> I know it's a strange request to want to preserve trailing spaces;
> most folks want to nuke them.  I'm working on a project where trailing
> spaces actually have meaning (it's how the developer prevents the
> automated semantecize tool from concatenating a long line of code
> that's intended to span multiple lines for readability).
>
> They have (probably inadvertently) installed Apex Emacs (aka aemacs),
> which is essentially plain old emacs 20.7.1 with Rational's Apex
> functionality integrated into the menu.  I'm glad they provided it,
> but I'm the only emacs user on the team, as everyone else is using the
> Rational's proprietary and very basic editor.
>
> So to get to the issue, emacs wipes out the trailing whitespace on
> every file I make a change to, and the semantizer rearranges code that
> I didn't touch, adding substantial noise to the diffs - which could
> frustrate reviewers.  How do I prevent emacs from nuking the trailing
> whitespace?
>
> Everything I've read indicates that emacs automatically preserves
> whitespace, and that it must be proactively configured to delete
> trailing whitespace.  My .emacs file is clean.  So somewhere in this
> aemacs installation, there must be a hook or something that I need to
> override.  How would I discover where that's happening?  Is it the
> lisp code for Ada-mode?

It looks like your `write-file-hooks' deletes whitespace.

Can you check the value of this variable when you have opened a buffer
with your source code?  I don't have any local write-file-hooks loaded
right now, so when I type `M-: (list write-file-hooks)' my message
buffer shows:

    (nil)

If yours shows a non-nil list of hooks, you should examine the hooks to
see if one (or more) of them calls `delete-trailing-whitespace' or some
other custom function with a similar effect.

- Giorgos

Re: Preserving trailing spaces

[jgombos]

Giorgos Keramidas wrote:
> 
> It looks like your `write-file-hooks' deletes whitespace.
> 
> Can you check the value of this variable when you have opened a buffer
> with your source code?  I don't have any local write-file-hooks loaded
> right now, so when I type `M-: (list write-file-hooks)' my message
> buffer shows:
> 
>     (nil)
> 
> If yours shows a non-nil list of hooks, you should examine the hooks to
> see if one (or more) of them calls `delete-trailing-whitespace' or some
> other custom function with a similar effect.
> 
Thanks for the tip.  That's useful to know.  I listed the write-file-hooks,
and the result was (nil).
Dieter Wilhelm's solution worked [which was to add (setq
ada-clean-buffer-before-saving nil) to .emacs], so it must have been a major
mode hook that removed the trailing whitespace.
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Re: Preserving trailing spaces

[Giorgos Keramidas]

jgombos <nabble.forum.jog@spamgourmet.com> writes:
> Giorgos Keramidas wrote:
>> It looks like your `write-file-hooks' deletes whitespace.
>> 
>> Can you check the value of this variable when you have opened
>> a buffer with your source code?  I don't have any local
>> write-file-hooks loaded right now, so when I type `M-: (list
>> write-file-hooks)' my message buffer shows:
>> 
>>     (nil)
>> 
>> If yours shows a non-nil list of hooks, you should examine the
>> hooks to see if one (or more) of them calls
>> `delete-trailing-whitespace' or some other custom function
>> with a similar effect.
> 
> Thanks for the tip.  That's useful to know.  I listed the
> write-file-hooks, and the result was (nil).  Dieter Wilhelm's
> solution worked
> [which was to add (setq ada-clean-buffer-before-saving nil) to
> .emacs], so it must have been a major mode hook that removed
> the trailing whitespace.

Nice.  I didn't know about `ada-clean-buffer-before-saving' :)