support case of cargo outputting empty lines

[Davidster]

When trying to debug a unit test from the parry rust crate, I got an error in the codelldb vscode extension. Here was my launch config:

{
  "type": "lldb",
  "request": "launch",
  "name": "Debug unit tests in library 'parry3d'",
  "cargo": {
    "args": [
      "test",
      "--package=parry3d"
    ],
    "filter": {
      "name": "parry3d",
      "kind": "lib"
    }
  },
  "args": [],
  "cwd": "${workspaceFolder}"
}

and here was the error:

Running `cargo test --package=parry3d --message-format=json`...
Error: Cargo invocation failed.
    at t.Cargo.getCargoArtifacts (/home/david/.vscode/extensions/vadimcn.vscode-lldb-1.9.2/extension.js:1:15379)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at Object.open (/home/david/.vscode/extensions/vadimcn.vscode-lldb-1.9.2/extension.js:1:13689)
Caused by: Error: Could not parse JSON: ""
    at Interface.<anonymous> (/home/david/.vscode/extensions/vadimcn.vscode-lldb-1.9.2/extension.js:1:16948)
    at Interface.emit (node:events:513:28)
    at Interface._onLine (node:readline:491:10)
    at Interface._normalWrite (node:readline:665:12)
    at Socket.ondata (node:readline:272:10)
    at Socket.emit (node:events:513:28)
    at addChunk (node:internal/streams/readable:315:12)
    at readableAddChunk (node:internal/streams/readable:289:9)
    at Socket.Readable.push (node:internal/streams/readable:228:10)
    at Pipe.onStreamRead (node:internal/stream_base_commons:190:23)

I suspect this is caused by the new lines added at the end of the message but I'm not sure

[vadimcn]

The cargo command is supposed to build targets only, not run them. See discussion here.

[Davidster]

Oh I see, so it's a problem with the way the launch configs are auto-generated. Is that process managed by the extension or by vscode itself?

[vadimcn]

The generated config should have included --no-run. Are you sure it was not modified afterwards?

[Davidster]

it seems that you were right and that this was caused by me having removed the "--no-run" argument. thanks for the help!

what would you think about adding a hint in the error message:

let hint = line.trim() === "" ? ". Did you remove the --no-run argument?" : "";
reject(new ErrorWithCause(`Could not parse JSON: "${line}"${hint}`, { cause: err }));