How to debug rust backend in mono repo project?

[raviSussol]

I have a mono repo project with frontend (react app) and backend (rust server). I want to debug backend using lldb from the root project folder where I can easily switch to the frontend when I need to. I tried to setup settings.json with lldb.launch.cwd configuration and other lldb.launch.relativePathBase etc but didn't work at all. I also tried to configure launch.json file something like this:

{
      "type": "lldb",
      "request": "launch",
      "name": "Debug executable 'app_server'",
      "cargo": {
        "args": ["build", "--bin=app_server", "--package=server"],
        "filter": {
          "name": "app_server",
          "kind": "bin"
        }
      },
      "cwd": "${workspaceFolder}/backend",
      "args": [],
    }

still that didn't work as well. If I open the backend separately in vscode then the debug just works fine but from the root folder how this lldb can be configured so that it can be debugged from the single vscode app?

My mono repo structure is something like:

├── my project
│   ├── .vscode
│   │   │   ├── launch.json
│   │   │   ├── settings.json
│   ├── frontend
│   │   ├── **/*.css
│   │   ├── **/*.tsx
│   ├── backend
│   │   ├── server
│   │   │   ├── src/*.rs
│   │   │   ├── cargo.toml
│   │   ├── service
│   │   │   ├── src/*.rs
│   │   │   ├── cargo.toml
│   │   ├── graphql
│   │   │   ├── src/*.rs
│   │   │   ├── cargo.toml
│   │   ├── cargo.toml

Any idea or help would be really appreciated.

Thanks.

[vadimcn]

What is the error? Can you attach a verbose.log?

[raviSussol]

@vadimcn Here's my output after trying to debug with lldb.

 *  Executing task: CodeLLDB: cargo 

Running `cargo build --bin=app_server --package=server --message-format=json`...
    Updating crates.io index
error: failed to get `graphql` as a dependency of package `server v0.1.0 (/Users/sussol/Documents/Git)`

Caused by:
  failed to load source for dependency `graphql`

Caused by:
  Unable to update /Users/sussol/Documents/graphql

Caused by:
  failed to read `/Users/sussol/Documents/graphql/Cargo.toml`

Caused by:
  No such file or directory (os error 2)
Error: Cargo invocation failed.
    at t.Cargo.getCargoArtifacts (/Users/sussol/.vscode/extensions/vadimcn.vscode-lldb-1.8.1/extension.js:1:11568)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at Object.open (/Users/sussol/.vscode/extensions/vadimcn.vscode-lldb-1.8.1/extension.js:1:9878)
Caused by: Error: exit code: 101.
    at ChildProcess.<anonymous> (/Users/sussol/.vscode/extensions/vadimcn.vscode-lldb-1.8.1/extension.js:1:13171)
    at ChildProcess.emit (node:events:526:28)
    at Process.ChildProcess._handle.onexit (node:internal/child_process:291:12)
 *  The terminal process terminated with exit code: 1. 
 *  Terminal will be reused by tasks, press any key to close it. 

I tried to enable log in lldb too by doing,

{
      "type": "lldb",
      "request": "launch",
      "name": "Debug executable 'app_server'",
      "cargo": {
        "args": ["build", "--bin=app_server", "--package=server"],
        "filter": {
          "name": "app_server",
          "kind": "bin"
        }
      },
      "cwd": "${workspaceFolder}/backend",
      "initCommands": ["log enable gdb-remote default"],
      "args": []

but didn't get any output in the "Debug Console" window.

[vadimcn]

I meant lldb.verboseLogging. But anyhow, the error seems plain enough - Cargo can't find the "graphql" dependency crate when building your project, so it never gets to the debugging phase.

[raviSussol]

So how to make cargo working in this case. Cause if I run the debugger from the backend folder opened in the vscode separately it just works. So don't think cargo needs to be updated in my environment variable. Am I missing anything to link cargo somewhere so that it can be worked from the root project folder in one vscode?

FYI, I also turned the "lldb.verboseLogging": true but couldn't get anything in the Debug Console window - probably cause the first hand error stopped to go further.

[vadimcn]

Sorry, I don't know. Try providing Cargo.toml path explicitly via --manifest-path maybe?

[raviSussol]

Ah lovely! Now it worked after providing Cargo.toml path explicitly. Thanks a lot @vadimcn for your help.