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bug#38252: 27.0.50; Gnus server definitions and generic function special
From: |
Eric Abrahamsen |
Subject: |
bug#38252: 27.0.50; Gnus server definitions and generic function specializers |
Date: |
Sun, 17 Nov 2019 14:31:13 -0800 |
I'm working on changing Gnus servers into structs, and replacing the
nnoo.el architecture with generic functions, and while I think I've got
a workable roadmap I'm running into some practical confusions. Stefan
I'm ccing you directly because I suspect you're the only one who knows
the answers to my questions :)
The approach is this: Change the server interface functions in
gnus-int.el into generic functions. Provide a generalizer that
recognizes current Gnus servers, and dispatches to the current function
definitions (using `gnus-get-function' and all that). Gradually change
the in-tree backends to be defined with cl-defstruct, and use normal
dispatching-on-struct for those. Eventually the legacy generalizer would
be left in place just to deal with old-style out-of-tree backends.
As an example, here's what `gnus-request-list' currently looks like:
--8<---------------cut here---------------start------------->8---
gnus-int.el:
(defun gnus-request-list (gnus-command-method)
(funcall (gnus-get-function gnus-command-method 'request-list)
(nth 1 gnus-command-method)))
nnimap.el:
(deffoo nnimap-request-list (&optional server)
<get IMAP group list>)
--8<---------------cut here---------------end--------------->8---
Afterward it would look like this:
--8<---------------cut here---------------start------------->8---
gnus-int.el:
(cl-defgeneric gnus-request-list (server)
"Docs and stuff.")
(cl-defmethod gnus-request-list ((server gnus-server-legacy))
(funcall (gnus-get-function server 'request-list)
(nth 1 server)))
nnimap.el:
(cl-defmethod gnus-request-list ((server gnus-server-imap))
<get IMAP group list>)
--8<---------------cut here---------------end--------------->8---
The nnimap version will dispatch on the `gnus-server-imap' defstruct,
that happens automatically. What I need is to be able to write a
generalizer/specializer that will recognize a legacy server (if calling
it "legacy" is annoying I can find something else) and dispatch on it.
The docstring of `cl-generic-define-generalizer' is gnomic, though I
found some better information in the docstring of
`cl-generic-generalizers', and looked at some of the existing
generalizer definitions.
Here's what I've worked up so far:
--8<---------------cut here---------------start------------->8---
(cl-generic-define-generalizer gnus-legacy-server-generalizer
90 (lambda (name &rest _) `(???)
(lambda (tag &rest _) (when (eq (car-safe tag) 'gnus-legacy-server)
(list tag))))
(cl-defmethod cl-generic-generalizers :extra "gnus-legacy-server" (thing)
"Dispatch on old-style Gnus server definitions."
(when wut?
(list gnus-legacy-server-generalizer)))
--8<---------------cut here---------------end--------------->8---
What I'm trying to do is fairly simple: if the argument is a list, and
the head of the list is a symbol that can be assoc'd into
`nnoo-definition-alist', and the second element is a string, then it's a
gnus-legacy-server. I just don't know where that test is supposed to go,
or why.
I understand this will probably be inefficient and ugly, but I hope that
before too long it would be a rare case that the generalizer is checked
at all.
Thanks,
Eric
- bug#38252: 27.0.50; Gnus server definitions and generic function specializers,
Eric Abrahamsen <=