How ReSharper found a bug in IDEA with the help of TeamCity

A history of one bug.

Several days ago, I received a message from one of ReSharper developers:

The link opened our internal TeamCity installation with the ReSharper build failed on sources checkout. The error was produced by SVN unable to update a directory:

svn: Failed to add directory 'test/assemblies': a versioned directory of the same name already exists

After some digging it turned out that the directory was deleted from the repository some time ago but was not deleted form the build agent. Then it was added anew and the build failed trying to add a directory that already existed on disk. The workaround was to invoke "Enforce clean checkout" from the TeamCity UI for the build configuration.

So ReSharper team can continue their current development effort on performance optimization, but why the directory was not deleted in the first place?

TeamCity uses SVNKit library to talk to Subversion repositories and luckily the developer of the library happened to be just a room away these days. Introduced into the issue he reached for the code to check and soon found a bug in the library that might result in not deleted directory in the working copy. It could only reproduce under certain optimization options that only two products are actually using, one of them being TeamCity and the other ... IntelliJ IDEA. But wait, IDEA is preparing for the 8.0 release these days!

No worries. As I am writing this, the library is already fixed, the latest build downloaded from SVNKit TeamCity installation and as I've just checked on our TeamCity server, the fix is already checked into IDEA release branch.

Actually, the bug is a rare one since it can reproduce only under certain circumstances, it was introduced not so long ago and was only included into EAP releases of IDEA and TeamCity.