Re: precedence of auto-mode-alist and magic-fallback-mode-alist

[Jason Rumney]

Stephen Berman wrote:
> On GNU Emacs 23.0.50.3 (i686-pc-linux-gnu, GTK+ Version 2.12.0) of
> 2007-11-29 on escher I do the following:
>
> 1. emacs -Q
> 2. M-x browse-url-emacs RET http://www.gnu.org RET
> 3. After a short time a buffer www.gnu.org pops up containing the HTML
> source of the gnu.org home page.  This buffer is in Org mode, because
> auto-mode-alist takes precedence over magic-fallback-mode-alist (if I
> save the buffer as "testme" then C-x C-f opens the file in html-mode).
>
> I don't remember if cases like this were considered when this precedence
> relation was established.  If not, is the above an argument against this
> precedence relation, or just evidence that we can't always DTRT, or is
> it a bug that can be fixed while retaining the current precedence
> relation?
>   

The word fallback in the variable name suggests that it is intended to
work this way. There is a corresponding magic-mode-alist which has
higher priority. But the real bug is that www.gnu.org is being treated
as a filename after being fetched by browse-url. It shouldn't be going
anywhere near auto-mode-alist.