bug#34898: 24.4; `message-separator' face only works for default value of `mail-header-separator'

["Basil L. Contovounesios" <contovob@tcd.ie>]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> The value of `mail-header-separator' gets added to
> `message-font-lock-keywords', which does the actual fontification. Using
> setq to change the value of `mail-header-separator' did not change the
> font lock keyword, despite setting the variable before message.el is
> loaded (or is it pre-loaded?). Using the customize interface to set
> `mail-header-separator' *does* work as expected.

0. emacs -Q
1. (setq mail-header-separator "--") C-j
2. C-x m

Note that setting mail-header-separator before loading message.el works
as expected.

3. M-x customize-variable RET mail-header-separator RET
4. Change value from "--" to "--foo--"
5. C-c C-c
6. C-x m

Note that "--foo--" gets inserted, but message-font-lock-keywords still
holds the value that mail-header-separator had at the time message.el
was loaded.

Since mail-header-separator lacks a custom setter, it makes no
difference whether you use setq or Customize, so long as its value is
changed before message.el is loaded.  Otherwise, you have to reevaluate
and reapply message-font-lock-keywords.

-- 
Basil