Add command to show LSP's internal state for diagnosing issues (#3195)

### Motivation

Add a command to trigger the new custom diagnose request, so that it's easy to see the information at a glance.

### Implementation

It's the same implementation as show syntax tree, we use a custom resource to show a read-only document containing the relevant information.

### Manual Tests

1. Launch the extension on this branch
2. On the second VS Code window, open the Ruby LSP code itself (you need the server changes to verify all pieces together)
3. Invoke the new command
4. Verify you see the internal state of the server

vscode/package.json

@@ -138,6 +138,11 @@
         "title": "Show syntax tree",
         "category": "Ruby LSP"
       },
+      {
+        "command": "rubyLsp.diagnoseState",
+        "title": "Diagnose language server state",
+        "category": "Ruby LSP"
+      },
       {
         "command": "rubyLsp.railsGenerate",
         "title": "Rails generate",

vscode/src/common.ts

@@ -20,6 +20,7 @@ export enum Command {
   RunTestInTerminal = "rubyLsp.runTestInTerminal",
   DebugTest = "rubyLsp.debugTest",
   ShowSyntaxTree = "rubyLsp.showSyntaxTree",
+  DiagnoseState = "rubyLsp.diagnoseState",
   DisplayAddons = "rubyLsp.displayAddons",
   RunTask = "rubyLsp.runTask",
   BundleInstall = "rubyLsp.bundleInstall",

vscode/src/documentProvider.ts

@@ -12,6 +12,9 @@ export default class DocumentProvider
       case "show-syntax-tree":
         response = uri.query;
         break;
+      case "show-diagnose-state":
+        response = uri.query;
+        break;
     }
 
     return response;

vscode/src/rubyLsp.ts

@@ -264,6 +264,10 @@ export class RubyLsp {
         Command.ShowSyntaxTree,
         this.showSyntaxTree.bind(this),
       ),
+      vscode.commands.registerCommand(
+        Command.DiagnoseState,
+        this.diagnoseState.bind(this),
+      ),
       vscode.commands.registerCommand(Command.ShowServerChangelog, () => {
         const version = this.currentActiveWorkspace()?.lspClient?.serverVersion;
 
@@ -779,6 +783,48 @@ export class RubyLsp {
     return this.getWorkspace(workspaceFolder.uri);
   }
 
+  private async diagnoseState() {
+    const workspace = await this.showWorkspacePick();
+
+    const response:
+      | {
+          workerAlive: boolean;
+          backtrace: string[];
+          documents: { uri: string; source: string };
+          incomingQueueSize: number;
+        }
+      | null
+      | undefined = await workspace?.lspClient?.sendRequest(
+      "rubyLsp/diagnoseState",
+    );
+
+    if (response) {
+      const documentData = Object.entries(response.documents);
+      const information = [
+        `Worker alive: ${response.workerAlive}`,
+        `Incoming queue size: ${response.incomingQueueSize}`,
+        `Backtrace:\n${response.backtrace.join("\n")}\n`,
+        `=========== Documents (${documentData.length}) ===========`,
+        ...documentData.map(
+          ([uri, source]) => `URI: ${uri}\n\n${source}\n===========`,
+        ),
+      ].join("\n");
+
+      const document = await vscode.workspace.openTextDocument(
+        vscode.Uri.from({
+          scheme: "ruby-lsp",
+          path: "show-diagnose-state",
+          query: information,
+        }),
+      );
+
+      await vscode.window.showTextDocument(document, {
+        viewColumn: vscode.ViewColumn.Beside,
+        preserveFocus: true,
+      });
+    }
+  }
+
   // Show syntax tree command
   private async showSyntaxTree() {
     const activeEditor = vscode.window.activeTextEditor;