weird bogosity relating to "copyright-update"

weird bogosity relating to "copyright-update"

[Miles Bader]

I use Emacs' copyright-updating stuff, which is generally really nice,
but for a few months it's been misbehaving in a way I found very
confusing...  I can't seem to reproduce it using a minimal
configuration.

Basically I enable it in my .emacs mode like this:

   (add-hook 'write-file-hooks 'copyright-update)

the `copyright-update' function is autoloaded by default from
"copyright.el".

This worked fine for years, but recently it's started giving an error
when saving a file:

  run-hook-with-args-until-success: Symbol's value as variable is void: copyright-update

... making the file-write fail.

Oddly, examining the state of Emacs afterwards, it's clear that
"copyright.el" _has_ been loaded by the autoload, but for some reason
the `copyright-update' variable -- which is defvar'd in copyright.el --
has become unbound, making the copyright-update function code always
fail thereafter.

The only way I can then save files, is to manually do "M-x load-library
RET copyright RET", upon which everything starts working properly.

However today I noticed another message which I hadn't before:

    Warning: defvar ignored because copyright-update is let-bound

... emitted while Gnus was saving some mail via FCC.

Now I can see what's going on:  Gnus ("lisp/gnus/nnfolder.el":1094) is
let-binding `copyright-update' _around_ the file write which results in
"copyright.el" being autoloaded, but the let-binding suppresses the
global binding, screwing up all writes once the original let-binding
exits.

So... what change tickled this problem, and what's the right way to fix
it...?  It doesn't seem a bad thing that Gnus is doing that let-binding
(you probably _don't_ want your mail FCCs to get copyright-updated), but
it's clearly bad that the let-binding is screwing things up...

Thanks,

-Miles

-- 
Admiration, n. Our polite recognition of another's resemblance to ourselves.

Re: weird bogosity relating to "copyright-update"

[Lars Ingebrigtsen]

Miles Bader <miles.bader.fz@renesas.com> writes:

> So... what change tickled this problem, and what's the right way to fix
> it...?  It doesn't seem a bad thing that Gnus is doing that let-binding
> (you probably _don't_ want your mail FCCs to get copyright-updated), but
> it's clearly bad that the let-binding is screwing things up...

Yes, that seems like the wrong way to do this.  If nnfolder wants to
let-bind `copyright-updated', it also has to require copyright.  But I
think it would make more sense for nnfolder to bind `write-file-hooks'
to nil, wouldn't it?

But it is puzzling that this has started happening lately.  That code in
nnfolder seems to have been committed in 2005, but it only started
erroring out quite recently.

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen

Re: weird bogosity relating to "copyright-update"

[Miles Bader]

Lars Ingebrigtsen <larsi@gnus.org> writes:
> But it is puzzling that this has started happening lately.  That code in
> nnfolder seems to have been committed in 2005, but it only started
> erroring out quite recently.

Hmm, there's the additional twist that `copyright-update' is a
buffer-local variable, which might make things even more messy.

Don't really know tho...

-Miles

-- 
Genealogy, n. An account of one's descent from an ancestor who did not
particularly care to trace his own.

Re: weird bogosity relating to "copyright-update"

[Stefan Monnier]

>> So... what change tickled this problem, and what's the right way to fix
>> it...?  It doesn't seem a bad thing that Gnus is doing that let-binding
>> (you probably _don't_ want your mail FCCs to get copyright-updated), but
>> it's clearly bad that the let-binding is screwing things up...
> Yes, that seems like the wrong way to do this.  If nnfolder wants to
> let-bind `copyright-updated', it also has to require copyright.

Indeed.

> But I think it would make more sense for nnfolder to bind
> `write-file-hooks' to nil, wouldn't it?

Actually, the recommended hook to use for copyright-update nowadays is
not write-file-hooks (which has been marked obsolete since Emacs-22.1)
but before-save-hook.
So it should maybe bind write-file-functions, write-contents-functions,
and before-save-hook, or and maybe after-save-hook as well.

Or maybe a better way would be to use write-region rather than save-buffer.


        Stefan