433632 - Doubly escaped ampersands in RSS links results in duplicate messages in feed

Status: RESOLVED DUPLICATE of bug 258465

(MailNews Core :: Feed Reader, defect)

Description

[James]

User-Agent:       Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9b5) Gecko/2008050509 Firefox/3.0b5
Build Identifier: 20080505

If in an RSS feed, the link URL contains a doubly escaped ampersand, for example, from an Atom feed:

<link rel="alternate" href="http://www.example.com/page?id=10&amp;amp;comment=12" />

Thunderbird is unable to associate the entry in the atom feed with the existing entry that it has already downloaded.  Consequently, every time it downloads the feed it considers that entry as new, and so it gets duplicated every time.

This affects both Thunderbird 2 and 3.

Note that it is highly likely that any application sending a doubly escaped ampersand has a bug in it (as the above link would mean there was a parameter called amp;comment, very unlikely), but I think Thunderbird should still be able to handle it correctly without duplicating the entry, even if the link is broken.

Reproducible: Always

Steps to Reproduce:
1.Subscribe to a feed that contains a link that has a doubly escaped ampersand
2.Click get mail to download the feed
3.Click get mail again to download the feed again
Actual Results:  
The entry with the doubly escaped ampersand appears twice (and keeps appearing again for every subsequent click of get mail).

Expected Results:  
The entry should only appear once.

Here is an example feed that can be used to reproduce the problem:

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:taxo="http://purl.org/rss/1.0/modules/taxonomy/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/" xmlns:dc="http://purl.org/dc/elements/1.1/">
  <title>Example</title>
  <link rel="alternate" href="http://www.example.com" />
  <subtitle>Example subtitle</subtitle>
  <id>http://www.example.com</id>
  <entry>
    <title>Example Entry</title>
    <link rel="alternate"
        href="http://www.example.com/page?id=10&amp;amp;comment=12" />
    <author>
      <name>John Smith</name>
    </author>
    <published>2008-05-13T23:18:30Z</published>
    <summary type="html">
        Summary text
    </summary>
    <dc:creator>John Smith</dc:creator>
    <dc:date>2008-05-13T23:18:30Z</dc:date>
  </entry>
</feed>

Comment 1

[Joshua Cranmer [:jcranmer]]

Bug 258465 is one of the RSS duplicate bugs that cites the ampersand problem directly (indeed the first one I checked). RESO DUP.