tried many variations of the vanilla vscode language setup, till I go…

…t the basic tests working...

.gitignore

@@ -131,4 +131,5 @@ dist
 
 archives
 .temple
-.DS_Store
+.DS_Store
+.build

env/temple-language/client/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "temple-language-client",
+  "description": "Adds syntax highlighting, formatting, auto-completion, jump-to-definition and linting for a custom.",
+  "version": "0.0.13",
+  "license": "MIT",
+  "scripts": {
+    "build": "tsc"
+  },
+  "dependencies": {
+    "vscode-languageclient": "9.0.1"
+  }
+}

env/temple-language/client/src/index.ts

@@ -0,0 +1,28 @@
+import type { ExtensionContext } from './language/LanguageClient';
+
+import path from 'path';
+import LanguageClient, { useBasic } from './language/LanguageClient';
+
+let client: LanguageClient;
+
+export function activate(context: ExtensionContext) {
+  // The server is implemented in node
+  const server = context.asAbsolutePath(path.join('server', 'out', 'index.js'));
+
+  client = useBasic({
+    id: 'languageServerExample',
+    label: 'Language Server Example',
+		language: 'plaintext',
+    server: server
+  });
+
+  // Start the client. This will also launch the server
+  client.activate();
+}
+
+export function deactivate() {
+  if (!client) {
+    return undefined;
+  }
+  return client.deactivate();
+}

env/temple-language/client/src/language/LanguageClient.ts

@@ -0,0 +1,95 @@
+export type { ExtensionContext } from 'vscode';
+export type ClientOptions = {
+  id: string,
+  label: string,
+  server: string,
+  language: string,
+  scheme?: string,
+  watcher?: string
+};
+
+import { workspace } from 'vscode';
+import {
+	LanguageClient as VSLanguageClient,
+	LanguageClientOptions,
+	ServerOptions,
+	TransportKind
+} from 'vscode-languageclient/node';
+
+export default class LanguageClient {
+  // The vscode language client
+  protected _client: VSLanguageClient;
+
+  /**
+   * Makes a new vscode language client
+   */
+  constructor(
+    id: string,
+    label: string,
+    serverOptions: ServerOptions, 
+    clientOptions: LanguageClientOptions
+  ) {
+    // Create the language client and start the client.
+    this._client = new VSLanguageClient(
+      id,
+      label,
+      serverOptions,
+      clientOptions
+    );
+  }
+
+  /**
+   * Starts the client
+   */
+  activate() {
+    // Start the client. This will also launch the server
+    return this._client.start();
+  }
+
+  /**
+   * Stops the client
+   */
+  deactivate(): Thenable<void> | undefined {
+    return this._client.stop();
+  }
+}
+
+export function useBasic(options: ClientOptions) {
+  const { 
+    id, 
+    label, 
+    server, 
+    language, 
+    scheme = 'file', 
+    watcher = '**/.clientrc' 
+  } = options;
+
+  // If the extension is launched in debug mode 
+  // then the debug server options are used
+  // Otherwise the run options are used
+  const serverOptions: ServerOptions = {
+    run: { module: server, transport: TransportKind.ipc },
+    debug: {
+      module: server,
+      transport: TransportKind.ipc,
+    }
+  };
+
+  // Options to control the language client
+  const clientOptions: LanguageClientOptions = {
+    // Register the server for plain text documents
+    documentSelector: [{ scheme, language }],
+    synchronize: {
+      // Notify the server about file changes to 
+      // '.clientrc files contained in the workspace
+      fileEvents: workspace.createFileSystemWatcher(watcher)
+    }
+  };
+
+  return new LanguageClient(
+    id,
+    label,
+    serverOptions,
+    clientOptions
+  );
+}

env/temple-language/client/tsconfig.json

@@ -0,0 +1,14 @@
+{
+	"compilerOptions": {
+		"esModuleInterop": true,
+		"module": "commonjs",
+		"target": "es2020",
+		"lib": ["es2020"],
+		"outDir": "out",
+		"rootDir": "src",
+		"sourceMap": true,
+		"types": []
+	},
+	"include": ["src"],
+	"exclude": ["node_modules"]
+}