Debugging VSCode plugin and the language server
Prerequisites
-
Install LLDB and the LLDB Extension.
-
Open the root folder in VSCode. Here you can access the preconfigured debug setups.
-
Install all TypeScript dependencies
cd editors/code npm ci
Common knowledge
- All debug configurations open a new
[Extension Development Host]VSCode instance where only therust-analyzerextension 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 installedrust-analyzerbinary.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 Ctrl+Shift+P 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-analyzerserver on Linux you might need to enableptracefor 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:[profile.dev] debug = 2 -
Select
Run Extension (Debug Build)to run your locally builttarget/debug/rust-analyzer. -
In the original VSCode window once again select the
Attach To Serverdebug configuration. -
A list of running processes should appear. Select the
rust-analyzerfrom this repo. -
Navigate to
crates/rust-analyzer/src/main_loop.rsand add a breakpoint to theon_requestfunction. -
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)
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
RUSTFLAGS='--cfg debug_assertions' cargo build --release
Demo
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.