To make this happen, just configure your Eclipse to debug your Spark applications as a regular Scala code debug. To configure select Run | Debug Configuration | Scala Application as shown in the following figure:

Suppose we want to debug our KMeansDemo.scala and ask Eclipse (you can have similar options on InteliJ IDE) to start the execution at line 56 and set the breakpoint in line 95. To do so, run your Scala code as debugging and you should observe the following scenario on Eclipse:

Then, Eclipse will pause on the line you ask it to stop the execution in line 95, as shown in the following screenshot:

In summary, to simplify the preceding example, if there is any error between line 56 and line 95, Eclipse will show where the error actually occurs. Otherwise, it will follow the normal workflow if not interrupted.