# Debugging VSCode plugin and the language server ## Prerequisites - Install [LLDB](https://lldb.llvm.org/) and the [LLDB Extension](https://marketplace.visualstudio.com/items?itemName=vadimcn.vscode-lldb). - 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 ci ``` ## Common knowledge * All debug configurations open a new `[Extension Development Host]` VSCode instance where **only** the `rust-analyzer` extension being debugged is enabled. * To activate the extension you need to open any Rust project folder in `[Extension Development Host]`. ## Debug TypeScript VSCode extension - `Run Installed Extension` - runs the extension with the globally installed `rust-analyzer` binary. - `Run Extension (Debug Build)` - runs extension with the locally built LSP server (`target/debug/rust-analyzer`). TypeScript debugging is configured to watch your source edits and recompile. To apply changes to an 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 - When attaching a debugger to an already running `rust-analyzer` server on Linux you might need to enable `ptrace` for unrelated processes by running: ``` echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope ``` - By default, the LSP server is built without debug information. To enable it, you'll need to change `Cargo.toml`: ```toml [profile.dev] debug = 2 ``` - Select `Run Extension (Debug Build)` to run your locally built `target/debug/rust-analyzer`. - In the original VSCode window once again select the `Attach To Server` debug configuration. - A list of running processes should appear. Select the `rust-analyzer` from this repo. - Navigate to `crates/rust-analyzer/src/main_loop.rs` and add a breakpoint to the `on_request` function. - Go back to the `[Extension Development Host]` instance and hover over a Rust variable and your breakpoint should hit. If you need to debug the server from the very beginning, including its initialization code, you can use the `--wait-dbg` command line argument or `RA_WAIT_DBG` environment variable. The server will spin at the beginning of the `try_main` function (see `crates\rust-analyzer\src\bin\main.rs`) ```rust let mut d = 4; while d == 4 { // set a breakpoint here and change the value d = 4; } ``` However for this to work, you will need to enable debug_assertions in your build ```rust RUSTFLAGS='--cfg debug_assertions' cargo build --release ``` ## 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 `rust-analyzer` process It could be a case of just jumping the gun. The `rust-analyzer` 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 `rust-analyzer` Make sure you have run `echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope`. By default this should reset back to 1 every time 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`.