Rust debugging in VS Code

General
,
1

I’m trying to set up a debugger in VS Code (actually Codium) on Linux. Does anyone already have this working?

If so, can you share your launch.json. I think I’m almost there but the debugger doesn’t seem to launch. I’m getting no errors I can find, when I ‘run’ the debug toolbar appears for about a second and then disappears.

Solution

Here’s a summary of how I solved this for Ubuntu 19.04 with VS Codium:
Summary of what worked for Ubuntu 19.04:

	sudo apt-get install lldb
	rustup component add rls rust-analysis rust-src

In VS Codium

  • Add extension: rust-lang
  • In settings:
    change rust server from RLS to rust-analyzer
    optional: change editor settings to ‘reformat on save’ (useful if you plan to work with Maidsafe code which requires this as well as using clippy).

That should be it. I recommend ignoring anything that tells you to create a cargo build task in tasks.json or a debugger config in settings.json as this seems to break the Rust-Lang extension!

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2

I dont have a debugger going per se. I get type feedback etc w the rust package with rust-analyzer for running check (for my money its way better than RLS).

I know that’s not really what you’re asking, but in case it’s helpful :+1:

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3

All tips welcome, thanks Josh. I have that installed and may even have seen its output but tbh is hard to know what is generating the output I’ve seen. I can see the simple cargo build output, and I’ve seen a very long list of warnings (maybe from analyser, maybe from clippy) but I’m not sure how to control all this goodness yet.

Main issue is the debugger though.

4

As Josh mentioned, rust-analyzer is pretty good. Debugging depends on what you want to debug. If it’s a library then you’ll need a test to do debugging. If it’s a binary then that can be debugged easily.

Once you’ve installed rust-analyzer and it has completed the build. You’ll know it’s done when this cargo check [...] goes away:
image

Then above the test function or the main function of your binary you should see Run | Debug options.
Clicking to the left of the line number places a break point (a red dot).

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5

Thanks Lionel, do you have a launch.json you can share?

I have lldb-mi in my launch.json config (for syncer which is a command line app). I can set a breakpoint but from what I am seeing I don’t think LLDB is starting. It looks to me as if VS Code tries to start it, waits for a connection and times out after a second, but there are no errors anywhere. So it might help to see a working config.

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You don’t really need a launch.json when using rust-analyser. I remember configuring a debugger using launch.json back when I was using RLS (which is now deprecated).

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Debug",
            "program": "${workspaceFolder}/target/debug/safe_core-as576asd57asdf4",
             "args": ["create_login_packet", "--" ,"--nocapture"],
            "cwd": "${workspaceFolder}"
        }
    ]
}

Here’s an old launch config that was lying around

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Well there’s a clue - I’ve followed instructions which say I need to create the config. Maybe that’s the problem. Thanks, gives me some things to try, starting with deleting my launch.json! :smile:

8

Having tried a few things I’m puzzled.

I’m using VSCodium on Linux and was originally set up with the native debugger ennabled (which includes LLDB) and had added the rust-lang extention which includes support for build tasks and the docs say:

Rust support is powered by a separate language server - either by the official Rust Language Server (RLS) or rust-analyzer, depending on the user’s preference. If you don’t have it installed, the extension will install it for you (with permission).

I thought I had rust-analyzer installed because I wasn’t prompted for it, but it isn’t in my extensions list so I’ve been trying to install it as an extension but it doesn’t show up (instructions here don’t work - they just paste a search into the extensions list which doesn’t find rust-analyzer). So I don’t think it is in the market place.

This may explain why I don’t get an option to debug unless I create a launch.config, but when I do that (just tried using safe-vault) I can run the debugger but get the result above (debug toolbar appears for a second and then disappears).

So I’m puzzled as to how VS Codium is supposed to be set up (seems you guys are using an extension I can’t install. Maybe superceded by the rust-lang extension which I can’t get to work.

I don’t think save_vault is being run, and if I mess with the config (e.g. change the name of the executable to safe_NOTHING) the behaviour doesn’t change. I can set a breakpoint in safe_vault.js but it has no effect.

Looking in VSC settings I had RLS selected, so I switched to rust-analyzer. No difference!

UPDATE:
Seems like this might be the magic needed: sudo apt-get install lldb
I’ve not seen any instructions to do that!

VS Codium has now prompted me to install rust-analyzer, so fingers crossed.

BINGO! That’s the missing step, installing lldb

9

It is still not quite as promised. It only works with a launch.json config, which is fine.

If I use the little |> Run|Debug buttons inside the code I get an error popup and it doesn’t run the debugger:
command 'rust-analyzer.runSingle' not found

But if I create a simple config in launch.json and run that it’s fine, and I hit my breakpoint.

10

Solution

Here’s a summary of how I solved this for Ubuntu 19.04 with VS Codium:
Summary of what worked for Ubuntu 19.04:

	sudo apt-get install lldb
	rustup component add rls rust-analysis rust-src

In VS Codium

  • Add extension: rust-lang
  • In settings:
    change rust server from RLS to rust-analyzer
    optional: change editor settings to ‘reformat on save’ (useful if you plan to work with Maidsafe code which requires this as well as using clippy).

That should be it. I recommend ignoring anything that tells you to create a cargo build task in tasks.json or a debugger config in settings.json as this seems to break the Rust-Lang extension!

1 Like