bug#22206: 25.1.50; doc string of `define-minor-mode'

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Drew Adams]

Unlike (elisp) `Defining Minor Modes', the doc string does not say that
LIGHTER is a string and that keyword :lighter has a string value.
Please mention that the value is a string.

In GNU Emacs 25.1.50.1 (i686-pc-mingw32)
 of 2015-12-04
Bzr revision: ffefb6e899fbcdcbd79cb34292d57b7bc3043fcc
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk --enable-checking=yes
 --enable-check-lisp-object-type --without-compress-install 'CFLAGS=-Og
 -ggdb3' LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Eli Zaretskii]

> Date: Fri, 18 Dec 2015 09:52:39 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> Unlike (elisp) `Defining Minor Modes', the doc string does not say that
> LIGHTER is a string and that keyword :lighter has a string value.
> Please mention that the value is a string.

The doc string says:

  Optional LIGHTER is displayed in the mode line when the mode is on.

What else could it possibly be, except a string?

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Dmitry Gutov]

On 12/18/2015 09:32 PM, Eli Zaretskii wrote:

> What else could it possibly be, except a string?

A form in the format described in mode-line-format. And that works, 
actually, so I'm not sure we should document it to be more limited.

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Eli Zaretskii]

> Cc: 22206@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Fri, 18 Dec 2015 21:41:35 +0200
> 
> On 12/18/2015 09:32 PM, Eli Zaretskii wrote:
> 
> > What else could it possibly be, except a string?
> 
> A form in the format described in mode-line-format. And that works, 
> actually, so I'm not sure we should document it to be more limited.

Exactly.

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Drew Adams]

> > What else could it possibly be, except a string?
> 
> A form in the format described in mode-line-format. And that works,
> actually, so I'm not sure we should document it to be more limited.

IMO, we should document what it needs to be.  If it can be more than
a string, then we should document just what it can be.  And in that
case the manual (which states that it is a string) should likewise
be updated to say what the value can be.

bug#22206: 25.1.50; doc string of `define-minor-mode'

[Drew Adams]

> > Unlike (elisp) `Defining Minor Modes', the doc string does not say that
> > LIGHTER is a string and that keyword :lighter has a string value.
> > Please mention that the value is a string.
> 
> The doc string says:
>   Optional LIGHTER is displayed in the mode line when the mode is on.
> 
> What else could it possibly be, except a string?

Tons of things can be displayed in the mode line, including symbols.
"Displayed" does not preclude producing a string representation of
the thing to be displayed.  And users of this macro should not need
to know intricacies of how things can be displayed in the mode line.
They should be told what the type of LIGHTER is, IMO.

But if you don't want to clarify this by adding one word, as in the
manual, then, well, don't.