(Focusing on Python because that's where I am 🙂) So turbo speed-run on DAP: Generic protocol Editors can opt into to allow language-agnostic debugging experience. Then lagnuage-specific server does the language-specific finagling under the hood. Python's DAP is

debugpy

: https://github.com/microsoft/debugpy So essentially there's two halves: • A

debugpy

server must be launched with the relevant code running • Your Editor (like VS Code) connects to it via a client, and sends the breakpoint and other info to it. So if you wanted to do this today (try it!) Put the following at the top of your code:

import debugpy
debugpy.listen(5678)  # Thats the port, localhost by debugpy.wait_for_client()

Running your code (

./pants test --debug

or

./pants run

) then launches the server and waits for connection. In your editor pick the "remote attach" option using the right port. Then F5 to launch the debugger. This connects to the server and tells it the current debugging info (breakpoints and other settings). 🎉

What does this have to do with Pants?

We can add an option to Pants to launch the relevant DAP when requested, so no code instrumentation is needed.

debugpy

comes with a "launched" out of the box for this. So (and details to be discussed)

./pants debug <spec>

would run your code with the DAP server launched and waiting for a connection.

I gotta get a PoC going, we can figure out the right CLI sauce though

DAP is lightly related to BSP, as it is the protocol supported by `debugSession/start`: https://build-server-protocol.github.io/docs/specification.html#debug-request

we don’t support it yet for Scala, but we’d like to

An alternative is to add

--use-dap

to

run

and

test

Demo: