Sometimes, after we close a bug because we fix it, or because it is a duplicate of another bug, or because the symptoms have gone away — invalid and wontfix bugs are a little different — people come along that have a problem that they believe is identical to the original bugreport. Quite often, they end up commenting on the “old” bugreport and say something along the lines of “hey, this is not fixed yet” or “this broke again” or “why did you close this bug, I’m still seeing this”!

In 99% of cases, I (and many other people) ask people in this situation to file a new bug.

The reasons why we do this vary a little, but on the whole they tend to be pretty similar, and so I figured it would be worth documenting them. In no particular order, we prefer new bugs over reopening closed ones because:

• More often than not, issues with similar symptoms can be caused by different factors. In Firefox’s case, these can be the version of Firefox, add-ons, different preferences/options that people have selected, third-party software, network setup, hardware and drivers, the OS people are using (Mac, Linux, Windows (what version?), …), changes in public web pages involved with the bug, … it’s a pretty long list. Different causes will require different fixes, and tracking them in the same bug will lead to confusion very quickly.
• We close bugs as fixed when we land patches. We track the uplift of the patches that landed for a bug in that bug. Reopening a bug that has already had patches landed in the tree, especially once they’ve been uplifted and released, confuses tracking the state of those patches, and any new patches that we write to fix the same issue.
• The old bug will have investigation and discussion of the problem as originally reported. If we now start investigating the new issue in the same place, with the old summary and the old comments, testcases, attachments, steps to reproduce, reporter, etc., we will eventually get confused. This relates to the first point: quite often there are subtle differences. Keeping track of those once we have two reports in a single bug, and ensuring we address the issue fully is difficult, often impossible.
• Bugzilla sends a lot of email, and is geared towards communication with flags and email. If you report an issue by commenting in another one, the “reporter” role of that bug is still the old reporter, and the CC list includes all the reporters of the duplicate bugs that were filed, the assignee will be the person who landed the last few patches (but they might not be able to fix the newly-reported thing, or might even have left Mozilla altogether), and so on and so forth. This confuses the “needinfo” flag, spams all those people about an issue they might no longer be seeing, and generally leads to still more confusion.
• People track open bugs they are assigned to, and new bugs in certain components. New comments (on closed bugs) are much, much more likely to get lost in the daily bugmail avalanche – which means your issue won’t get fixed.
• Comments are almost always low on details. Comments are often “this still doesn’t work”, with no indication of any of the environmental factors that impact where and when people see bugs (see the earlier point). When people file new bugs, we immediately get more information, normally at least the operating system and version of Firefox involved, and if people are careful about how they file the bug and describe its symptoms or steps to reproduce, we might learn about differences in the steps they’re using, compared to the old bug.
• New bugs are cheap! Bugzilla has more than 1.1 million bugreports in it. Another one won’t hurt. Worst case scenario, we can mark it as a duplicate of the old one…

It might be interesting if we had an easy way to split a comment into a new bug, though that would still defeat some of the points raised earlier. In the meantime though, think twice before commenting on older, closed bugs with a “this is still broken” comment!

How do I get attention for my newly filed bug? Email to all the people on this old bug seems much more likely to get attention!

First off, this strategy can be detrimental in many cases (see e.g. this or this – or just consider how much “email to all the people…to get attention” sounds like “spam”).

Second, we get a lot of bugreports. We’re working on ensuring they get triaged effectively. This should already be a lot better than it was a few months ago (see this post by Benjamin Smedberg), and will continue to improve.

Finally… if you file a bug that is extremely similar to an old bug, it seems fair to me to leave a comment in the old bug, mark the new bug as blocking the old bug, and/or set the needinfo flag for the assignee (if available) of the fixed bug, to draw their attention to this new bug.