debug-adapter-protocol VS watchpoints

> There's a strange dance of IDEs coming and going, with their idiosyncracies and partial plugins.

The Language Server Protocol [1] is the best thing to happen to text editors. Any editor that speaks it gets IDE features. Now if only they'd adopt the Debug Adapter Protocol [2]...

[1] https://microsoft.github.io/language-server-protocol/

[2] https://microsoft.github.io/debug-adapter-protocol/

Wonder if they've got support for Debug Adapter Protocol? https://microsoft.github.io/debug-adapter-protocol/

> Debuggers need to do more things

It's true that coming up with an interface for an abstract debugger is harder, but it's not impossible. Microsoft create Debug Adapter Protocol (https://microsoft.github.io/debug-adapter-protocol/), which is conceptually similar for LSP. It's not perfect, but covers most basic operations pretty well, while leaving to the debugger to deal with the implementation details.

Most languages also include support for the Debug Adapter Protocol, and Haskell is no exception, so if you are so inclined, you can hook up your favorite editor/IDE and go to town.

They're working on the Debug Adapter Protocol but it doesn't have critical mass/adoption yet. And yeah, I end up having a fair share of dbg!(foo). It's not so bad since dbg!() also returns its value, so you don't have to mess with your code too much.

TL;DR: What would it take to implement a Debug Adapter Protocol (DAP)-based step debugger?

RDP is the Windows Remote Desktop Protocol that was in use for decades before VSCode; VSCode's own remoting doesn't use it.

I'd say that, in addition to LSP, the other big thing that came out of VSCode is DAP: https://microsoft.github.io/debug-adapter-protocol.

The most important part is the JDT Languag Server, it will give you the Java tooling for writing code. I think it has DAP support as well, so with a DAP client like nvim-dap you should be able to debug as well.

It's sad that Python does not really support some of these debugging methods.

E.g. you cannot really watch variable changes. There are some workarounds, like writing a custom __setattr__ or __setattribute__ in case of an object, or checking all STORE_* operations. https://youtrack.jetbrains.com/issue/PY-30387 https://github.com/gaogaotiantian/watchpoints

Reverse debugging is also sth I would like to have, and there are a few projects to support this, but it's not really well supported in standard CPython. https://foss.heptapod.net/pypy/revdb https://pytrace.com/

There is also the watchpoints module to track changes to variables, but I don't think you can use the two of them together since they both use the same underlying callback in Python.

It uses Python's built-in inspect module to get the caller frame. https://github.com/gaogaotiantian/watchpoints/blob/68bc13716...

It then uses sys.settrace (which is intended as an interface for debuggers) to step through the code and check whether the variable has been changed. Documentation on sys.settrace: https://docs.python.org/3/library/sys.html#sys.settrace

Python exposes most of its guts as part of the standard library, making clever hacks like this possible.