[Question] How to develop a vscode plugin to Influence debugging behavior

[vipcxj]

I have developed a library JAsync to add async/await support to Java. The library converts the await function to a callback at the bytecode level. At least for now, at the level of writing code, with this library, users already have the same experience with async/await as they do with csharp and js. However, during debugging, when the user breaks to the line containing the await, the user expects the code to stop at the next line after executing the next step, but in reality, the code jumps to the inside of the one function that handles callbacks in the JAsync framework. Because the actual code has become a callback, the code on paper is not executed immediately. I want change this behavior. I have tried writing a jvmti agent. But I found breakpoint event is exclusive. Since jdwp has reuqested the breakpoint event right, my agent can't achieve it again. So I decide to develop a plugin of ide to fix it. Here is my thought. For example:

var a = someFunc().await();  // line 1
System.out.println(a); // line 2

will be converted to this in byte code:

someFunc().then(a -> {  // line 1
    System.out.println(a);  // line 2
})

If user add a breakpoint to line 1, And the progrem has topped at line 1. In my plugin, I can get report of it, So my plugin will add a breakpoint to real line2 in the lambda method which JAsync generated. When the user press the step over button, my plugin execute continue instead of step over, when the progrem stop at line 2, my plugin will remove the breadpoint. I came here to ask you guys How can I develop such a plugin that only changes part of the behavior of the current debugging plugin, instead of starting from scratch and writing a new one?

[testforstephen]

You can take a look at "Run to Cursor" feature, which is very similar to your want.