GNU bug report logs - #24543
25.1; describe-symbol doesn't show face with same name as a variable

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Alex <agrambot <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.1; describe-symbol doesn't show face with same name as a variable
Date: Sun, 25 Sep 2016 12:49:11 -0600

Recipe:

emacs -Q
C-h o font-lock-comment-face RET

Only the variable of this name is shown, not the face (which can be
viewed with describe-face, of course).

It appears that when the face only shares a name with a function, then
both the function and face are shown. Only a variable shadows the face
in describe-symbol.

Message #8 received at 24543 <at> debbugs.gnu.org (full text, mbox):

From: Alex <agrambot <at> gmail.com>
To: 24543 <at> debbugs.gnu.org
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Fri, 16 Jun 2017 15:54:45 -0600

[Message part 1 (text/plain, inline)]

Alex <agrambot <at> gmail.com> writes:

> Recipe:
>
> emacs -Q
> C-h o font-lock-comment-face RET
>
> Only the variable of this name is shown, not the face (which can be
> viewed with describe-face, of course).
>
> It appears that when the face only shares a name with a function, then
> both the function and face are shown. Only a variable shadows the face
> in describe-symbol.

This is because describe-symbol isn't returning (buffer-string) like
describe-{function, variable} are.

I've attached a patch fixing this problem.

Additionally, I have attached another patch that re-orders the placement
of variables/faces in describe-symbol, to put more emphasis on the
variable entry rather than the face.

[0001-Properly-show-faces-in-describe-symbol-Bug-24543.patch (text/x-diff, attachment)]

[0002-lisp-help-mode.el-describe-symbol-backends-Reorder-e.patch (text/x-diff, attachment)]

Message #11 received at 24543 <at> debbugs.gnu.org (full text, mbox):

From: Alex <agrambot <at> gmail.com>
To: 24543 <at> debbugs.gnu.org
Cc: Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Tue, 25 Jul 2017 22:28:05 -0600

Alex <agrambot <at> gmail.com> writes:

> Alex <agrambot <at> gmail.com> writes:
>
>> Recipe:
>>
>> emacs -Q
>> C-h o font-lock-comment-face RET
>>
>> Only the variable of this name is shown, not the face (which can be
>> viewed with describe-face, of course).
>>
>> It appears that when the face only shares a name with a function, then
>> both the function and face are shown. Only a variable shadows the face
>> in describe-symbol.
>
> This is because describe-symbol isn't returning (buffer-string) like
> describe-{function, variable} are.
>
> I've attached a patch fixing this problem.
>
> Additionally, I have attached another patch that re-orders the placement
> of variables/faces in describe-symbol, to put more emphasis on the
> variable entry rather than the face.

Ping. Eli?

Message #14 received at 24543 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Alex <agrambot <at> gmail.com>
Cc: 24543 <at> debbugs.gnu.org
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Wed, 26 Jul 2017 17:45:48 +0300

> From: Alex <agrambot <at> gmail.com>
> Cc: Eli Zaretskii <eliz <at> gnu.org>
> Date: Tue, 25 Jul 2017 22:28:05 -0600
> 
> Ping. Eli?

Sorry, I hoped someone more knowledgeable about this stiff will beat
me to it.

I will review this in a couple of days.

Message #17 received at 24543 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Alex <agrambot <at> gmail.com>
Cc: 24543 <at> debbugs.gnu.org
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Fri, 28 Jul 2017 10:35:02 +0300

> From: Alex <agrambot <at> gmail.com>
> Date: Fri, 16 Jun 2017 15:54:45 -0600
> 
> > emacs -Q
> > C-h o font-lock-comment-face RET
> >
> > Only the variable of this name is shown, not the face (which can be
> > viewed with describe-face, of course).
> >
> > It appears that when the face only shares a name with a function, then
> > both the function and face are shown. Only a variable shadows the face
> > in describe-symbol.
> 
> This is because describe-symbol isn't returning (buffer-string) like
> describe-{function, variable} are.
> 
> I've attached a patch fixing this problem.

Thanks.  This LGTM, but doesn't the fact that describe-face's return
value will change after this constitute an incompatible change?  And
if so, could it break some of the users of this function out there?

Message #20 received at 24543 <at> debbugs.gnu.org (full text, mbox):

From: Alex <agrambot <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 24543 <at> debbugs.gnu.org
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Fri, 28 Jul 2017 14:45:24 -0600

Eli Zaretskii <eliz <at> gnu.org> writes:

>> From: Alex <agrambot <at> gmail.com>
>> Date: Fri, 16 Jun 2017 15:54:45 -0600
>> 
>> > emacs -Q
>> > C-h o font-lock-comment-face RET
>> >
>> > Only the variable of this name is shown, not the face (which can be
>> > viewed with describe-face, of course).
>> >
>> > It appears that when the face only shares a name with a function, then
>> > both the function and face are shown. Only a variable shadows the face
>> > in describe-symbol.
>> 
>> This is because describe-symbol isn't returning (buffer-string) like
>> describe-{function, variable} are.
>> 
>> I've attached a patch fixing this problem.
>
> Thanks.  This LGTM, but doesn't the fact that describe-face's return
> value will change after this constitute an incompatible change?  And

I suppose so; would it be expected to be documented in NEWS?

> if so, could it break some of the users of this function out there?

Potentially, but I don't see that being an issue in this case. The
return value isn't documented, so users shouldn't be (and likely aren't)
relying on describe-face always returning nil. It makes more sense to
treat describe-face like describe-{function, variable}.

Though I'm not sure why those two procedures return (buffer-string) in
the first place. In any case, I figure it's better to leave those and
describe-symbol alone and just make describe-face behave similarly.

Message #25 received at 24543-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Alex <agrambot <at> gmail.com>
Cc: 24543-done <at> debbugs.gnu.org
Subject: Re: bug#24543: 25.1;
 describe-symbol doesn't show face with same name as a variable
Date: Sat, 05 Aug 2017 11:53:00 +0300

> From: Alex <agrambot <at> gmail.com>
> Cc: 24543 <at> debbugs.gnu.org
> Date: Fri, 28 Jul 2017 14:45:24 -0600
> 
> > if so, could it break some of the users of this function out there?
> 
> Potentially, but I don't see that being an issue in this case. The
> return value isn't documented, so users shouldn't be (and likely aren't)
> relying on describe-face always returning nil. It makes more sense to
> treat describe-face like describe-{function, variable}.

OK, I pushed the changes.

Thanks.

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