Dealing with processes is not a trivial task, sadly.
From the terminal, arara prints the compilation status and ends, as expected. When called from editors, I believe it's a matter on how each developer decided to handle process input/output. From TeXworks, things seem smooth, even if it requires user interaction. I once once a problem with TeXnicCenter when trying to rerun pdflatex: the last process call got stuck somehow and files were locked. The only way to have my files "released" was to kill the offending process via task manager, so things started working again.
TeXnicCenter gave me a couple of headaches in the past, so I still believe there's nothing I could do on my end (the arara part). That said, it's worth mentioning that Windows behaves quite differently from Unix.
arara is a Java program. Any calls to arara will redirect to a call to java -jar arara.jar and the Java Virtual Machine will be in charge of the execution. In Unix, we have that as a shell script (thanks to Karl for the suggestion), and in Windows, it's an .exe; both are, in fact, wrappers to the .jar itself. Maybe, maybe TeXnicCenter is confused with the .exe resolving to a call to the JVM. What I can suggest is the following:
Try replacing the call to C:\Program Files\arara\arara.exe in TeXnicCenter with a direct call to the JVM with java -jar "C:\Program Files\arara\arara.jar", followed of course by the editor parameters. At least now we are "skipping" one expansion from the wrapper to a VM call. But this is just a thought, I have no Windows machine around to test it. :(
Sorry for the imprecise answer, but sadly the solution (if any) is on uncharted territory. As I mentioned before, calling stuff from stuff is very tricky and, most of the time, we just get the idea from phenomena observation. :(
I'm in the middle of developing a new version. I'll see what can be done when dealing with processes. That's also a hint for me to set a Windows VM. At least I'll have Windows inside a cage, where it should be. :)
\begin{tikzpicture}(without space).\begin{ tikzpicture}is just wrong, so there is no reason to expectlualatex,araraor any other TeX tool to process it correctly! – Xavier Aug 07 '13 at 13:35:)My good friend percusse mentioned a similar behaviour before, and I suspect it's somehow related to the way the editor handles external processes (I assume the issue is not reproduced whenararais called from the terminal Update: percusse just confirmed this). I have no Windows machine at the moment, but I'll try to set up a VM and take a closer look at everything, from the JVM memory allocation withararato the API calls from TeXnicCenter. Sorry for the trouble. – Paulo Cereda Aug 07 '13 at 14:24arara: pdflatexandarara: xelatx, too, as well as with and without--shell-escaperesp.arara: lualatex: { shell: yes }. Same behavior. There are not always two instances opened of the engines. Can't reproduce when for now. – LaRiFaRi Aug 07 '13 at 14:25araraas it looks great. But I will stop that for the moment, as it would disturb my working. Should I report something to TC? Not sure what, if I am honest. (Edit: and please don't apologize! Can't remember I paid something...) – LaRiFaRi Aug 07 '13 at 14:28:)– Paulo Cereda Aug 07 '13 at 14:46