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I've recently found that I am unable to successfully debug my Play projects in IntelliJ. I was able to debug just fine a week ago, but I must have done something to alter some configuration because I am currently observing some strange behaviors in IntelliJ. Here's what's happening:

  • I can load up my Play project in Intellij and successfully connect to the target VM with my debug configuration (set-up as described in the Play debug tutorial). The console prints the "Connected to the target VM, address: 'localhost:9999', transport: 'socket'" line as expected.
  • I then run the application and everything still works as expected; my project compiles and runs just fine. However, when I go to set breakpoints, I am sometimes unable to set them at all - clicking the column on the side will do nothing and selecting the "toggle breakpoint" option from the menu also doesn't create a breakpoint. This only happens in some controllers. In others, I am able to set a breakpoint, but there isn't a check mark or "X" in the icon and the application does not catch the breakpoint. The strangest thing is that while testing I have had a few breakpoints that have worked.
  • I've tried just about everything I can think of to try and get these breakpoints to be fully functional again. I've run "play clean", I've recreated the IDEA module with "play idea", I've invalidated my caches in IDEA, I've uninstalled and re-installed the Play and Scala plugins in IDEA, and I've restarted my machine several times. The only thing I feel like I haven't tried would be a re-install of IDEA, but I don't really get why that would work where these other solutions haven't.

Has anyone in this group ever run into anything like this? Googling the issue mostly results in tutorials on how to set-up debugging. I don't recall changing anything about my project having to do with debugging. Since I last remember debugging working, I've really only changed things in the application's controllers and views, which to my knowledge, would have no effect on this issue. I'm running IntelliJ IDEA 12.1.4 Ultimate and Play 2.1.1. Any help with this would be much appreciated.

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Sometimes all IDEA problems are solved after you've cleaned its cache, have you tried to call invalidate caches? –  4lex1v Aug 7 '13 at 6:56
I have had that problem as well. It was appearing when the code inspection started to fail (the green/yellow/red marks in the right column). The code inspection would only show an eye and never complete. At that time I also had problems with my debugging. I never really solved it, I think my project had some severe problems that corrupted IntelliJ's indexing. I created a new fresh project instead, the first one was more or less a POC so it didn't bother me to start from scratch. I can't tell if you have the same problem and I can't say if recreating the project is an option for you. –  maba Aug 7 '13 at 17:11
Unfortunately, I've already tried the "Invalidate caches" option, but that did not produce any results. I haven't tried starting a new project/recreating my project, but I've tried a few others that I had previously made and they all exhibit the same issues. I have re-run "play idea," but that hasn't made a difference either. The JetBrains support person I've spoken with has had me try multiple versions of IDEA, but none of the versions improve the debugging issue. The EAP versions print some StackOverflow errors originating from the Scala plugin, so I thing it has something to do with that. –  Brian Aug 7 '13 at 21:55
Have you tried using the Play 2.0 support plugin of IDEA for debugging instead of setting up a configuration as explained in the Play tutorials? (see here how to do that) –  Aerus Aug 8 '13 at 13:53

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