530ee4ff8a
add note about passing cfg(debug_assertions) to rustc on build. The server will not spin without this arcane hack
100 lines
3.6 KiB
Markdown
100 lines
3.6 KiB
Markdown
# Debugging VSCode plugin and the language server
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## Prerequisites
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- Install [LLDB](https://lldb.llvm.org/) and the [LLDB Extension](https://marketplace.visualstudio.com/items?itemName=vadimcn.vscode-lldb).
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- Open the root folder in VSCode. Here you can access the preconfigured debug setups.
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<img height=150px src="https://user-images.githubusercontent.com/36276403/74611090-92ec5380-5101-11ea-8a41-598f51f3f3e3.png" alt="Debug options view">
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- Install all TypeScript dependencies
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```bash
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cd editors/code
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npm ci
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```
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## Common knowledge
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* All debug configurations open a new `[Extension Development Host]` VSCode instance
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where **only** the `rust-analyzer` extension being debugged is enabled.
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* To activate the extension you need to open any Rust project folder in `[Extension Development Host]`.
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## Debug TypeScript VSCode extension
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- `Run Installed Extension` - runs the extension with the globally installed `rust-analyzer` binary.
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- `Run Extension (Debug Build)` - runs extension with the locally built LSP server (`target/debug/rust-analyzer`).
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TypeScript debugging is configured to watch your source edits and recompile.
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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]`
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```
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> Developer: Reload Window
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```
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## Debug Rust LSP server
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- When attaching a debugger to an already running `rust-analyzer` server on Linux you might need to enable `ptrace` for unrelated processes by running:
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```
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echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
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```
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- By default, the LSP server is built without debug information. To enable it, you'll need to change `Cargo.toml`:
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```toml
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[profile.dev]
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debug = 2
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```
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- Select `Run Extension (Debug Build)` to run your locally built `target/debug/rust-analyzer`.
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- In the original VSCode window once again select the `Attach To Server` debug configuration.
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- A list of running processes should appear. Select the `rust-analyzer` from this repo.
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- Navigate to `crates/rust-analyzer/src/main_loop.rs` and add a breakpoint to the `on_request` function.
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- Go back to the `[Extension Development Host]` instance and hover over a Rust variable and your breakpoint should hit.
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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`)
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```rust
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let mut d = 4;
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while d == 4 { // set a breakpoint here and change the value
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d = 4;
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}
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```
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However for this to work, you will need to enable debug_assertions in your build
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```rust
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RUSTFLAGS='--cfg debug_assertions' cargo build --release
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```
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## Demo
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- [Debugging TypeScript VScode extension](https://www.youtube.com/watch?v=T-hvpK6s4wM).
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- [Debugging Rust LSP server](https://www.youtube.com/watch?v=EaNb5rg4E0M).
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## Troubleshooting
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### Can't find the `rust-analyzer` process
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It could be a case of just jumping the gun.
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The `rust-analyzer` is only started once the `onLanguage:rust` activation.
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Make sure you open a rust file in the `[Extension Development Host]` and try again.
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### Can't connect to `rust-analyzer`
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Make sure you have run `echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope`.
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By default this should reset back to 1 every time you log in.
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### Breakpoints are never being hit
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Check your version of `lldb`. If it's version 6 and lower, use the `classic` adapter type.
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It's `lldb.adapterType` in settings file.
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If you're running `lldb` version 7, change the lldb adapter type to `bundled` or `native`.
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