Metals: Debugger for scala in vscode

[virtualdvid]

I have been searching a lot how to debug scala in vscode without success. Wondering if there is a way or if you guys are working on that at the moment?.

[tgodzik]

We are working on it, but there is still some way to go.

[virtualdvid]

Awesome, this will put more users of scala in vscode. This's a common frustration I found online and we end using eclipse (which I don't like) Thanks for your answer!

[olafurpg]

Since https://github.com/scalacenter/bloop/pull/1087 was merged into Bloop, it's possible to breakpoint debug Scala/Java sources that are defined in the workspace. After #1010, it will be possible to debug 3rd party libraries as well. Once that's merged then this issue can be closed.

[ctataryn]

I'm curious, the Bloop documentation states:

_If you want to debug your code with Bloop via an editor such as VS Code, vim, Sublime or emacs you can use Metals._ [1]

Are they just jumping the gun on their decree?

[1] - https://scalacenter.github.io/bloop/docs/debugging-reference#debugging-via-an-editor

[tgodzik]

@ctataryn It's not yet possible, from what I see we still need to finish a couple of things.

[gabro]

v0.8.0 is out, supporting this feature! Check out the release notes https://scalameta.org/metals/blog/2020/01/10/cobalt.html#debugging

[virtualdvid]

Hi, Thank you for this release! I'm getting an issue.

I created a hello.scala script to test it. In the cmd:

C:\Users\myuser\project\scala\my_project>scala hello.scala
Hello World!

But when I use the debugger option in vscode nothing happens:

This is happening in my personal and job laptop.

[ctataryn]

@virtualdvid when I debug, what happens is above the Hello object there’d be a “Run | Debug” insight that appears.

Click on the “M” icon on the left toolbar, then run the “Doctor” to see if there are any problems. I know for me it wasn’t until I upgraded my project’s Scala version that it all started working.

[virtualdvid]

Hi @ctataryn, Thanks for your answer. I got several bugs solved. I did it from scratch since uninstalling vscode. I'm getting now all test in doctor passing:

Same result as before, the debugger is not running.

[ctataryn]

@virtualdvid Hmmm, I'm not entirely sure then. What you could do is exit VSCode, remove the .metals folder, then re-start VSCode and the extension should ask you about "importing" your project again.

As a side note: I just opened VSCode an my Main.scala file was auto-loaded in a tab. I noticed that the Run | Debug options didn't appear until I switched to a different file, and then went back to Main.scala.

[virtualdvid]

@ctataryn I did what you said the same result on both laptops. Can you share your launch,json file?. I'm curious how that looks like. Thanks!

EDIT
Checking the logs the only warning is:
WARN no build target for: C:\Users\david\Documents\Documents\scala\my_proyect\src\main\hello.scala

my build.sbt

name := "MyProject"

version := "0.1"

organization := "MyMegaCorp"

scalaVersion := "2.12.10"

sbtVersion := "1.2.8"

[ctataryn]

@virtualdvid actually the extension doesn't use launch.json and I don't recognize the "Debug and Run Start" pane you have there on the left. Perhaps it is another extension that's interfering? Here's a shot of extensions that I have installed, I'd suggest disabling all but Metals and any other essential extensions you may need.

👉 And also, double check to see that your Metals extension is at v1.7.2 👈

[virtualdvid]

@ctataryn Thanks for your help. I don't know what happened. I turned on my job laptop today and it is working. In my personal laptop stills the issue. Weird!

[tgodzik]

WARN no build target for: C:\Users\david\Documents\Documents\scala\my_proyect\src\main\hello.scala usually means that the build was either not imported of the directory structure does not correspond to that exported from the build tool.

[olafurpg]

Thank you everybody for reporting back feedback! I encourage you to open a new issue to discuss bugs/problems you encounter. This issue here was mainly about introducing basic debugging functionality.

Debugging is a new feature with a large surface area so it's better to have focused issues on specific functionality. We are also aware that there are also some important features missing like run configurations (see https://github.com/scalameta/metals-feature-requests/issues/63)

[mrseanryan]

Am having a similar issue with debug not working - it seems to connect to the debug session, but never reaches the 1st breakpoint. It just sits there:

Output pane:

INFO  time: compiled forcomp in 0.95s
INFO  Listening for transport dt_socket at address: 56516
INFO  tracing is enabled: C:\Users\str_i\AppData\Local\scalameta\metals\cache\dap-server.trace.json
INFO  tracing is enabled: C:\Users\str_i\AppData\Local\scalameta\metals\cache\dap-client.trace.json
INFO  Starting debug proxy for [Main]
INFO  Trying to attach to remote debuggee VM localhost:56516 .
INFO  Attaching to debuggee VM succeeded.

note: I run debug by clicking the 'debug' link above the main entry point:

note: if I click on run it does run OK.

In the log there is a similar warning to what @virtualdvid had:

WARN  no build target for: C:\sean\github\mrseanryan\scala-learning\projects\week6\tryout\src\main\scala\tryout\Main.scala

So maybe my project structure is incorrect 🤔

Perhaps someone could point me to a small example project, where debugging works ok ?

btw thanks for making this extension!

[olafurpg]

Please open new tickets to start new discussions or ask questions.