The problem:

I had an auto-generated task (TODO) from creating a class that implemented an interface. At some point, I noticed the task comment was gone, but the task indicator (checkbox icon) was still there. Probably because I have it set to reformat on save, but maybe I deleted the task comment without hitting the task button (or both). Anyway, I could not clear it no matter what:

• Double clicking the icon didn’t work since it couldn’t find the comment.
• Clicking the “Clean and Redetect Tasks” button did nothing.
• Restarting Eclipse (which I do more often than a Windows admin reboots), did naught.
• The Task View displayed the offending tasks, but the Delete option was greyed out. Selecting the task and hitting delete 3 million times while cursing furiously at the screen brought no justice.

The solution:

1. Go to Window >> Preferences, then Java/Compiler/Task Tags. Select the TODO task tag, or whatever accursed tag haunts you.
2. Click Remove. When it threatens a rebuild, call it’s bluff (that is, agree). When it’s done (and it took its sweet time), the offending tasks will be gone. Rejoice!
3. Click New… and restore the TODO tag. All legitimate TODO tasks will be restored.  Callooh! Callay!

keywords: can’t delete tasks, task tags, eclipse 3.4, mylyn

Not good.

The last thing I had done was add a Spring @Autowired annotation. I saved the file and voila, everything goes to crap. I then spend a stupid amount of time trying to track down the cause. I took the changes out. I did a clean and rebuild and retest (everything passed; this was Eclipse-only). I added new classes to see if they broke (they did). I did a false modify (add space, remove space, save) to see if that broke said file (it did). It was a death spiral. No matter how I changed the code, the same problem was there.

Turns out, it wasn’t the annotation, or anything else in Spring, or any of my code, or any of my Eclipse plugins. It was a step before that killed me. I was doing a little cleanup and I created a temp directory at the top of my project folder so I could move some files there. It wasn’t nested in anything, other than the top level directory. What could go wrong?

Apparently, that makes Eclipse see red. Squiggly red.

The solution was simply to do a refresh (F5) on my project. Just as quickly as it started, the problem went away. That smells like a bug to me, but if it was I figure I’d see a lot more mentions in Google or the Eclipse bug tracker. I’m really hoping this helps someone save some time.

Update: If that doesn’t help you, see more solutions in the comments. Thanks to those who contributed them.

Keywords: false error, bogus error, eclipse bug