GNU bug report logs - #31394
„gnus-newsgroup-headers” not reduced to limited to articles

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Felix Dietrich <felix.dietrich <at> sperrhaken.name>
To: submit <at> debbugs.gnu.org (The Gnus Bugfixing Girls + Boys)
Subject: „gnus-newsgroup-headers” not reduced to
 limited to articles
Date: Wed, 09 May 2018 23:22:27 +0200

[Message part 1 (text/plain, inline)]

Gnus v5.13
GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.28)
 of 2018-02-19, modified by Debian
--------------------

Hello,

I was dabbling around with creating a custom limiting function and came
upon „gnus-summary-limit-to-predicate”.  Upon using it I noticed that it
call the predicate not with only the current limited set of articles
shown in the summary buffer but with the superset of what I assume are
all the already fetched headers.  That is: „gnus-newsgroup-headers”
(used in the loop in „gnus-summary-limit-to-predicate”) does not get
reduced to contain only the articles in the current limited set like
„gnus-newsgroup-data” (used in other limiting functions).

  Comparing the length of „gnus-newsgroup-headers” and
  „gnus-newsgroup-data” before and after limiting was applied

    (length gnus-newsgroup-data)
    => 154
    (length gnus-newsgroup-headers)
    => 154

    (gnus-summary-limit-to-subject "gnus")

    (length gnus-newsgroup-data)
    => 75
    (length gnus-newsgroup-headers)
    => 154

That the predicate was called with articles from
„gnus-newsgroup-headers” not in „gnus-newsgroup-data” became an issue
when I tried to further limit an already limited set of articles: I was
selecting each article and the pseudo article test in
„gnus-summary-select-article” identified those article numbers not in
„gnus-newsgroup-data” as referring to pseudo articles which caused an
error – or when setting the PSEUDO parameter to „t” caused a warning
messages (e.g. „Can’t find article 9450”).

Should „gnus-newsgroup-headers” contain only the reduced set of article
headers similar to „gnus-newsgroup-data”?  Is
„gnus-summary-limit-to-predicate” working, without that reduction, as it
is supposed to, always passing the unlimited set of articles to the
predicate?

I have also attach my function with which I noticed the described
behaviour as an example.

[Message part 2 (text/plain, inline)]

(defun my/gnus-summary-limit-to-orig-date-diff ()
  "Limit summary articles by X-Original-Date to Date difference"
  (interactive)
  (gnus-summary-limit-to-predicate
   (lambda (header)
     (let ((original-date) (date) (age-in-days 5)
           ;; copied from `gnus-summary-limit-to-bodies' (Gnus v5.13)
           (gnus-select-article-hook nil)	;Disable hook.
           (gnus-article-prepare-hook nil)
           (gnus-use-article-prefetch nil)
           (gnus-keep-backlog nil)
           (gnus-break-pages nil)
           (gnus-summary-display-arrow nil)
           (gnus-updated-mode-lines nil)
           (gnus-auto-center-summary nil)
           (gnus-display-mime-function nil)
           (gnus-mark-article-hook)
           ;; end of copied from `gnus-summary-limit-to-bodies'
           )
       ;; not setting PSEUDO paramter to `t' causes error
       (gnus-summary-select-article t t t (mail-header-number header))
       (with-current-buffer gnus-article-buffer
         (article-narrow-to-head)
         (gnus-article-goto-header "X-Original-Date")
         (setq original-date (safe-date-to-time (buffer-substring
                                                 (point)
                                                 (point-at-eol)))
               date (safe-date-to-time (mail-header-date header)))
         (not (time-less-p (time-subtract date original-date)
                           (days-to-time age-in-days)))))
     ))
  )

[Message part 3 (text/plain, inline)]

--
Felix Dietrich

Message #8 received at 31394 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Felix Dietrich <felix.dietrich <at> sperrhaken.name>
Cc: 31394 <at> debbugs.gnu.org
Subject: Re: bug#31394: „gnus-newsgroup-headers”
 not reduced to limited to articles
Date: Sat, 22 Jun 2019 15:46:29 +0200

Felix Dietrich <felix.dietrich <at> sperrhaken.name> writes:

> Should „gnus-newsgroup-headers” contain only the reduced set of article
> headers similar to „gnus-newsgroup-data”?  Is
> „gnus-summary-limit-to-predicate” working, without that reduction, as it
> is supposed to, always passing the unlimited set of articles to the
> predicate?

I think it's by design, so that the predicate can either narrow or widen
the limit.  If you only want to narrow it, check whether the article is
in gnus-newsgroup-limit in the predicate and only return a subset of that.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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