Does it make a difference to the debugger that it is Scala code I'm debugging?

I am wondering what difference it m开发者_JS百科akes to the debugger (Intellij IDEA + Scala plug-in) when I debug Scala code and not Java code. To my understanding, a debugger is tightly coupled with the language i.e. a Java debugger can not handle Scala code but apparently the JVM is the center of attention here meaning as long as it is byte-code, any debugger would do. right ?

IMPORTANT UPDATE: The problem was to give an example of how a byte-code debugger may be limiting for Scala. Assume a break point is reached and I don't want to go to the next line but I want the debugger to evaluate an Scala expression in the context of the application (e.g. I like to call an operator method from a singleton object). The debugger is stuck because it can not understand Scala. I have to do the transformation myself and input the resulting Java to the debugger. The problem is that only "breakpoint stuff" could be handled in byte-code level. What if you want to put an expression under watch? Debugger has to understand Scala to evaluate the watched expression,right? This time I'm sure I'm right. Vengeance is mine, Saith the Lord ;-)

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Short answer your assumptions are wrong.

The reason is the debugger does not care what language your debugging. It stops at breakpoints which in turn include the line of a particular source file. Note that the source file is merely text for you to read - the debugger never scans the source files. If you change the spot where source files are to another directory with a text file in the right directory w/ the right filename as a breakpoint that has been set, the debugger will happily show it when the breakpoint happens. Everytime you set a breakpoint your ide is telling the debugger hey scan this class for any byte code on this line and stop when you hit it. This of course does not work if your ide is attempting to compile the same text file into a class file - however it will work if you create fake text files as source for a jar file and do the source file mapping thing.

If one thinks about it, writing a simple template and compiling it while support debugging is not that difficult. Simply use asm to create all the print statements and tell asm this print statement is from the template file on this line. After that you can add more clever stuff while keeping things debuggable.