# Debugging vs Code plugin and the Language Server

Install [LLDB](https://lldb.llvm.org/) and the [LLDB Extension](https://marketplace.visualstudio.com/items?itemName=vadimcn.vscode-lldb).

Checkout rust rust-analyzer and open it in vscode.

```
$ git clone https://github.com/rust-analyzer/rust-analyzer.git --depth 1
$ cd rust-analyzer
$ code .
```

- To attach to the `lsp server` in linux you'll have to run:

  `echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope`

  This enables ptrace on non forked processes

- Ensure the dependencies for the extension are installed, run the `npm: install - editors/code` task in vscode.

- Launch the `Debug Extension`, this will build the extension and the `lsp server`.

- A new instance of vscode with `[Extension Development Host]` in the title.

  Don't worry about disabling `rls` all other extensions will be disabled but this one.

- In the new vscode instance open a rust project, and navigate to a rust file

- In the original vscode start an additional debug session (the three periods in the launch) and select `Debug Lsp Server`.

- A list of running processes should appear select the `ra_lsp_server` from this repo.

- Navigate to `crates/ra_lsp_server/src/main_loop.rs` and add a breakpoint to the `on_task` function.

- Go back to the `[Extension Development Host]` instance and hover over a rust variable and your breakpoint should hit.

## Demo

![demonstration of debugging](https://user-images.githubusercontent.com/1711539/51384036-254fab80-1b2c-11e9-824d-95f9a6e9cf4f.gif)

## Troubleshooting

### Can't find the `ra_lsp_server` process

It could be a case of just jumping the gun.

The `ra_lsp_server` is only started once the `onLanguage:rust` activation.

Make sure you open a rust file in the `[Extension Development Host]` and try again.

### Can't connect to `ra_lsp_server`

Make sure you have run `echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope`.

By default this should reset back to 1 everytime you log in.

### Breakpoints are never being hit

Check your version of `lldb` if it's version 6 and lower use the `classic` adapter type.
It's `lldb.adapterType` in settings file.

If you're running `lldb` version 7 change the lldb adapter type to `bundled` or `native`.