Support analysis / types with Rust Analyzer

Fixes #881
It still takes a bit until diagnostics arrive, but this way error messages from `cargo` are included as well.

src/langs/rust/rust.js

@@ -22,8 +22,12 @@ export function setup({ document }) {
       code_view.handleDiagnostics(params.diagnostics);
     },
   );
-
-  lspc.start().catch(console.error);
+  const cacheDir = GLib.get_user_cache_dir();
+  const rustAnalyzerCache = `${cacheDir}/rust_analyzer_cache`;
+  // It shouldn't be necessary to disable `useRustcWrapper`, stop doing that as soon as that issue is fixed
+  // https://github.com/rust-lang/rust-analyzer/issues/16565#issuecomment-1944354758
+  const initializationOptions = {"cargo": {"buildScripts": {"useRustcWrapper": false}}, "rust": {"analyzerTargetDir": rustAnalyzerCache}};
+  lspc.start(initializationOptions).catch(console.error);
 
   buffer.connect("modified-changed", () => {
     if (!buffer.get_modified()) return;

src/lsp/LSPClient.js

@@ -45,10 +45,10 @@ export default class LSPClient {
     };
   }
 
-  async start() {
+  async start(initializationOptions = {}) {
     this._start_process();
 
-    await this._initialize();
+    await this._initialize(initializationOptions);
     await this._didOpen();
 
     this.ready = true;
@@ -65,7 +65,7 @@ export default class LSPClient {
     return once(this, "ready");
   }
 
-  async _initialize() {
+  async _initialize(initializationOptions = {}) {
     const { capabilities, rootUri } = this;
 
     // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#initialize
@@ -74,6 +74,7 @@ export default class LSPClient {
       clientInfo,
       capabilities,
       rootUri,
+      initializationOptions,
       locale: "en",
     });