Opera bug in handling of Atom feeds

I use the Opera browser (currently version 9.62) not only as my browser, but also as my e-mail and feed reader. I had noticed that, sometimes, the link at the bottom of a feed (blog) post doesn't take me to the correct page. In particular, this was happening with the Atom feed for Tim Bray's 'ongoing' blog. Tim was one of the authors of the Atom specification for blog feeds; I know Tim, and I know his blog feed follows the Atom specification rigorously.

I wrote to Tim and asked him about it, and it appears that this a known bug in Opera's handling of Atom feeds, that it doesn't not correctly process relative URLs in Atom feeds. Apparently Opera has been doing this wrongly for some years now. For example, for Tim's most recent post, Opera shows the link the Web page as being

http://www.tbray.org/ongoing/CL-Rain

but the actual page URL is

http://www.tbray.org/ongoing/When/200x/2008/11/28/CL-Rain

What went wrong? Well, in the Atom feed for 'ongoing',

• the value of "/feed/id" is "http://www.tbray.org/ongoing/"
• the value of the first "/feed/entry/link/@href" is "CL-Rain"

and Opera appears to be concatenating these to produce the URL

http://www.tbray.org/ongoing/CL-Rain

However, that first "/feed/entry" has its "xml:base" set to "When/200x/2008/11/28/". What Opera should do is add this in the middle, to produce the correct URL

http://www.tbray.org/ongoing/When/200x/2008/11/28/CL-Rain

Anyway, I have now posted a bug for Opera (DSK-240409), so we can only wait and see now when it gets fixed. Fingers crossed that it's sooner, rather than later.