rust/docs/dev/debugging.md

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# Debugging vs Code plugin and the Language Server
## Prerequsities
- Install [LLDB](https://lldb.llvm.org/) and the [LLDB Extension](https://marketplace.visualstudio.com/items?itemName=vadimcn.vscode-lldb) VSCode extensions.
- Open the root folder in VSCode. Here you can access the preconfigured debug setups.
<img height=150px src="https://user-images.githubusercontent.com/36276403/74611090-92ec5380-5101-11ea-8a41-598f51f3f3e3.png" alt="Debug options view">
- Install all TypeScript dependencies
```bash
cd editors/code
npm i
```
## Common knowledge
* All debug configurations open new `[Extension Development Host]` VSCode instance
where **only** your `rust-analyzer` extension is enabled.
* To activate the extension you need to open any Rust project folder in `[Extension Development Host]`.
## Debug TypeScript VSCode extension
- `Run Extension` - runs the extension with the globally installed `ra_lsp_server` binary.
- `Run Extension (Dev Server)` - runs extension with the locally built LSP server (`target/debug/ra_lsp_server`).
TypeScript debugging is configured to watch your source edits and recompile.
To apply changes to already running debug process press <kbd>Ctrl+Shift+P</kbd> and run the following command in your `[Extension Development Host]`
```
> Developer: Reload Window
```
## Debug Rust LSP server
- 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
- Enable debug symbols in `Cargo.toml`:
```toml
[profile.dev]
debug = 2
```
2020-02-16 21:21:11 +00:00
- Select `Run Extension (Dev Server)` to run your locally built `target/debug/ra_lsp_server`.
- In the original VSCode window once again select `Attach To Server` debug configuration.
- 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
- [Debugging TypeScript VScode extension](https://www.youtube.com/watch?v=T-hvpK6s4wM).
- [Debugging Rust LSP server](https://www.youtube.com/watch?v=EaNb5rg4E0M).
## 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`.