bug#34685: 26.1; function nnrss-get-namespace-prefix always returns nil

[Noam Postavsky <npostavs@gmail.com>]

tags 34685 + moreinfo
quit

wenbushi <wenbushi@gmail.com> writes:

> The function "nnrss-get-namespace-prefix" in gnus/nnrss.el always
> returns nil, which causes the contents in "<content:encoded>" tag of
> an RSS XML not showing in the gnus article buffer.
>
> Here is a fix:
>
> --- nnrss.el    2019-02-28 20:02:29.224675750 +0800
> +++ nnrss-fixed.el      2019-02-28 20:02:04.534267796 +0800
> @@ -1031,7 +1031,7 @@
>    "Given EL (containing a parsed element) and URI (containing a string
>  that gives the URI for which you want to retrieve the namespace
>  prefix), return the prefix."
> -  (let* ((prefix (car (rassoc uri (cadar el))))
> +  (let* ((prefix (car (rassoc uri (cadar (nthcdr 2 (car el))))))

> the argument "el" in the function is a list of the parsed XML, like(some
> fields are ignored)
>
> ((rss ((version . "2.0") (xmlns:atom . "http://www.w3.org/2005/Atom"))
>       (channel ((xmlns:content . "http://purl.org/rss/1.0/modules/content/"))
>                (title nil "RSS title")
>                (item nil
>                      (title nil "article title")
>                      (content:encoded nil "article content")))))
>
> The function "nnrss-get-namespace-prefix" should extract tag
> "xmlns:content". But it only returns nil because "(cadar el)" matches
> nothing.

That's only due to the particular encoding of your RSS feed though,
isn't it?  I believe xmlns prefixes can technically go on any element in
a document; I expect the current code works for some feeds, and your fix
would break things for them.

We should gather some test cases to be able to fix this properly.