bug#3756: eval-after-load 'ffap vs provide at start of file

bug#3756: eval-after-load 'ffap vs provide at start of file

[Kevin Ryde]

Starting from emacs -Q, evaluating

    (progn
      (eval-after-load 'ffap
        '(setq ffap-newsgroup-heads (remove "misc" ffap-newsgroup-heads)))
      (require 'ffap))

gets an error

    void-variable ffap-newsgroup-heads

where I hoped the eval-after-load meant after ffap is available and
therefore its various variables exist.

It looks like ffap.el has (provide 'ffap) near the start of the file,
instead of at the end.  The end is usual so that eval-after-load can be
used on a feature symbol as above, is it?


In GNU Emacs 22.3.1 (i486-pc-linux-gnu, GTK+ Version 2.14.7)
 of 2009-03-31 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs22:/etc/emacs:/usr/local/share/emacs/22.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/22.3/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/22.3/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t

bug#3756: eval-after-load 'ffap vs provide at start of file

[Glenn Morris]

Kevin Ryde wrote:

> It looks like ffap.el has (provide 'ffap) near the start of the file,
> instead of at the end.  The end is usual so that eval-after-load can be
> used on a feature symbol as above, is it?

I don't see why the ffap one shouldn't be at the end, but as discussed
in the context of this very example last month, you cannot rely on
provide always being at the end of a file:

http://lists.gnu.org/archive/html/emacs-devel/2009-06/msg00202.html

I'll mention something about this in the doc of eval-after-load.

bug#3756: marked as done (eval-after-load 'ffap vs provide at start of file)

[Emacs bug Tracking System]

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Your message dated Sun, 05 Jul 2009 20:52:14 -0400
with message-id <81iqi663b5.fsf@fencepost.gnu.org>
and subject line Re: bug#3756: eval-after-load 'ffap vs provide at start of file
has caused the Emacs bug report #3756,
regarding eval-after-load 'ffap vs provide at start of file
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
message is talking about, this may indicate a serious mail system
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immediately.)


-- 
3756: http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=3756
Emacs Bug Tracking System
Contact owner@emacsbugs.donarmstrong.com with problems

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From: Kevin Ryde <user42@zip.com.au>
To: bug-gnu-emacs@gnu.org
Subject: eval-after-load 'ffap vs provide at start of file
Date: Sun, 05 Jul 2009 10:48:24 +1000
Message-ID: <87ljn4x8dj.fsf@blah.blah>

Starting from emacs -Q, evaluating

    (progn
      (eval-after-load 'ffap
        '(setq ffap-newsgroup-heads (remove "misc" ffap-newsgroup-heads)))
      (require 'ffap))

gets an error

    void-variable ffap-newsgroup-heads

where I hoped the eval-after-load meant after ffap is available and
therefore its various variables exist.

It looks like ffap.el has (provide 'ffap) near the start of the file,
instead of at the end.  The end is usual so that eval-after-load can be
used on a feature symbol as above, is it?


In GNU Emacs 22.3.1 (i486-pc-linux-gnu, GTK+ Version 2.14.7)
 of 2009-03-31 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs22:/etc/emacs:/usr/local/share/emacs/22.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/22.3/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/22.3/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t



[-- Attachment #3: Type: message/rfc822, Size: 1627 bytes --]

From: Glenn Morris <rgm@gnu.org>
To: 3756-done@emacsbugs.donarmstrong.com
Subject: Re: bug#3756: eval-after-load 'ffap vs provide at start of file
Date: Sun, 05 Jul 2009 20:52:14 -0400
Message-ID: <81iqi663b5.fsf@fencepost.gnu.org>


Doc fix for eval-after-load; ffap provide moved to end for 23.2.

bug#3756: eval-after-load 'ffap vs provide at start of file

[Kevin Ryde]

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Glenn Morris <rgm@gnu.org> writes:
>
> http://lists.gnu.org/archive/html/emacs-devel/2009-06/msg00202.html

I didn't see that.  Doing provide when a feature is not yet ready for
use would seem fairly dubious though, in normal circumstances.

> I'll mention something about this in the doc of eval-after-load.

provide could cross-reference eval-after-load, if that helped remind to
take care with what point it's called, perhaps per below.



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*** loading.texi	17 Mar 2009 10:34:05 +1100	1.10
--- loading.texi	08 Jul 2009 07:40:12 +1000	
***************
*** 733,742 ****
  associated with @var{feature} are or will be available for other Lisp
  programs.
  
! The direct effect of calling @code{provide} is to add @var{feature} to
! the front of the list @code{features} if it is not already in the list.
! The argument @var{feature} must be a symbol.  @code{provide} returns
! @var{feature}.
  
  If provided, @var{subfeatures} should be a list of symbols indicating
  a set of specific subfeatures provided by this version of
--- 733,743 ----
  associated with @var{feature} are or will be available for other Lisp
  programs.
  
! The direct effect of calling @code{provide} is if not already in
! @var{features} then to add @var{feature} to the front of that list and
! call any @code{eval-after-load} code waiting for it (@pxref{Hooks for
! Loading}).  The argument @var{feature} must be a symbol.
! @code{provide} returns @var{feature}.
  
  If provided, @var{subfeatures} should be a list of symbols indicating
  a set of specific subfeatures provided by this version of

bug#3756: eval-after-load 'ffap vs provide at start of file

[Glenn Morris]

Thanks; added.