regexp-based group parameters

[NAGY Andras <nagya@inf.elte.hu>]

NAGY Andras <nagya@inf.elte.hu> writes:

> Some of the group options can be set based on group and topic
> parameters as well as on group regexps (say, total-expiry).  Others
> only based on parameters (banner).  And perhaps some only based on
> regexps. :)
> 
> Shouldn't there be a unified way for doing stuff like this?

Let's summarize once more: many functions in Gnus behave differently,
depending on which group they operate on.  There is (was?) a tendency
among these functions to introduce a custom variable, containing a
regexp, to be matched against group names, to decide which groups they
are supposed to deal width.  (Examples include
gnus-total-expirable-newsgroups, gnus-mailing-list-groups,
gnus-permanently-visible-groups etc).  Generally, a group matching or
not one of these regexps defines a boolean parameter for that group.

There are other type of such variables, regexp->something alists
(e.g. gnus-posting-styles) which assign a parameter to a group, based
on its name.

Besides this, there is the group/topic parameters mechanism, where
parameters can be assigned directly, or based on the groups place in
the topic hierarchy.  Furthermore, this info is stored in the newsrc
file instead of being customizable by the user through a config file.

Many (but not all, and even if yes, see below) Gnus functions (posting
styles, expiry, etc) allow the user to specify group parameters via
the gnus-group-find-parameter API as well as the "non-standard" custom
regexp way.

Extending the find-parameter implementation to treat not only
group/topic parameters found in newsrc, but also those found in a
newly introduced regexp->param-list alist, would have the following
advantages:

* Gnus functions could use a single interface to fetch group
parameters based on both methods, without having to deal with regexp
matching and stuff.

* Users would be able to define every group parameter based on regexps
as well, in addition to the group/topic method.

* The latter would allow storing group parameters in a static config
file, suitable for using on several hosts, instead of the
host-dependent, ever-changing newsrc.eld.


While writing this, I have found gnus-define-group-parameter which is
close to what I am talking about.  This defines a function
(gnus-parameter-%s group) for fetching a parameter's value, and this
function makes use of gnus-parameter-%s-alist, which maps group
regexps to parameter values.

However, there are several problems with this:

* For now, only 7 group parameters are defined this way.

* For this reason, the rest of Gnus does not make use of these
functions, but uses gnus-group-find-parameter, which ignores the
contents of gnus-parameter-%s-alist.

* Group/topic parameters allow setting arbitrary variables, not only
`strict' parameters.

* There is still no way to assign multiple parameters to a set of
groups at once.

To demonstrate this: I cannot (but would like to) write the following
in my .gnus:

(setq gnus-parameters
   '(("mail\..*" (gnus-show-threads . nil)
                 (gnus-use-scoring . nil)
                 (gnus-summary-line-format .
                        "%U%R%z%I%(%[%d:%ub%-20,20f%]%) %s\n")
                 (gcc-self . t)
                 (dispaly . all))

     ("list\..*" (total-expire . t)
                 (broken-reply-to . t))))
     

I think the example speaks for itself.  (Setting everything in one
place, independetly of newsrc.eld and topic topology.)

Anyone willing to implement this?  Introducing the new variable (named
gnus-parameters above) and modifying gnus-group-find-parameter would
do the trick, I believe.


Andras