14

https://stackoverflow.com/feeds/tag/delphi

Trying to read it in Opera i was "greeted" with "1st line should be XML declaration" error.

I tried few validators:

  • 1
    No, it is not. First line is empty. Tried with the newest FF. – Polygnome Aug 24 '12 at 10:44
  • and it is exactly redundant 4 me. Redundant as line, not as empty one. English is not my native, sorry. – Arioch 'The Aug 24 '12 at 11:08
  • @Arioch'The: that comment was directed at a comment of mine, where I claimed the XML feed does start with a XML declaration. I've since retracted that comment to make it a full post below. – Martijn Pieters Aug 24 '12 at 11:09
  • Well, that's why it is baf idea to delete comments :-) Though i sometimes do it myself :-) – Arioch 'The Aug 24 '12 at 11:11
  • The problem is back again today. – Martijn Pieters Sep 14 '12 at 8:09
  • And fixed again: Feeds have stopped working – Martijn Pieters Sep 14 '12 at 11:00
7

A recent upgrade introduced a blank line above the xml declaration, breaking our feeds.

This has been fixed and we've already deployed the change. Feeds should be working correctly now.

11

I can confirm there is a validation error in the feed:

>>> import urllib2
>>> data = urllib2.urlopen('http://stackoverflow.com/feeds/tag/delphi').read()
>>> data[:10]
'\r\n<?xml ve'

There is a CRLF (carriage-return + newline) combo before the <?xml .. ?> declaration statement, and the XML 1.0 standard only allows for whitespace after that declaration:

prolog ::= XMLDecl? Misc* (doctypedecl Misc*)?

where Misc* is a comment, a processing instruction or whitespace. Without the CRLF the feed is otherwise valid.

CRLF normally delimits HTTP headers, so I suspect the header generation for feeds has a bug where one CRLF is appended too many to the header output.

  • or maybe some empty header getsadded at the end, if no sanity check catches it... – Arioch 'The Aug 24 '12 at 11:43
  • @Arioch'The: Yeah, that would be one reason for such a bug. – Martijn Pieters Aug 24 '12 at 11:45
  • Hehe, someone downvoted to disagree. What, may I ask, is there to disagree? That adding a CRLF to the start of a XML document doesn't make it malformed? – Martijn Pieters Aug 24 '12 at 13:58
  • maybe that since that is bug, the real answer would be fixing the code ? i just don't know how bugs are tracked on SO :-) – Arioch 'The Aug 24 '12 at 14:20
  • @Arioch'The: Sure, but I don't have the code access to make that fix. That's up to the StackExchange devs. We can help by diagnosing the exact nature of said bug though. – Martijn Pieters Aug 24 '12 at 14:24
  • Then sorry, no green V to You ;-) – Arioch 'The Aug 24 '12 at 14:27
  • 2
    @Arioch'The: Oh dear, not sure if I can live with that! :-P – Martijn Pieters Aug 24 '12 at 14:28

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