explain how to launch the thing

1 files changed, 62 insertions, 0 deletions

diff --git a/docs/dev/debugging.md b/docs/dev/debugging.md
new file mode 100644
index 000000000..f868e6998
--- /dev/null
+++ b/docs/dev/debugging.md
@@ -0,0 +1,62 @@
+# 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`.