prompt to install languageserver is not available

src/languageService.ts

@@ -9,7 +9,7 @@ import net = require('net');
 import url = require('url');
 import { LanguageClient, LanguageClientOptions, StreamInfo, DocumentFilter, ErrorAction, CloseAction, RevealOutputChannelOn } from 'vscode-languageclient/node';
 import { Disposable, workspace, Uri, TextDocument, WorkspaceConfiguration, OutputChannel, window, WorkspaceFolder } from 'vscode';
-import { DisposableProcess, getRpath, exec } from './util';
+import { DisposableProcess, getRpath, exec, isRPkgIntalled } from './util';
 
 export class LanguageService implements Disposable {
   private readonly clients: Map<string, LanguageClient> = new Map();
@@ -25,6 +25,16 @@ export class LanguageService implements Disposable {
 
   private async createClient(config: WorkspaceConfiguration, selector: DocumentFilter[],
     cwd: string, workspaceFolder: WorkspaceFolder, outputChannel: OutputChannel): Promise<LanguageClient> {
+    const installed = await isRPkgIntalled(
+      'languageserver', cwd, true,
+      'R package {languageserver} is required to enable R language service features such as code completion, function signature, find references, etc. Do you want to install it?',
+      'You may need to reopen an R file to start the language service after the package is installed.'
+    );
+
+    if (!installed) {
+      return undefined;
+    }
+
     let client: LanguageClient;
 
     const debug = config.get<boolean>('lsp.debug');
@@ -169,8 +179,10 @@ export class LanguageService implements Disposable {
           ];
           const client = await self.createClient(config, documentSelector,
             path.dirname(document.uri.fsPath), folder, outputChannel);
-          client.start();
-          self.clients.set(key, client);
+          if (client) {
+            client.start();
+            self.clients.set(key, client);
+          }
           self.initSet.delete(key);
         }
         return;
@@ -188,8 +200,10 @@ export class LanguageService implements Disposable {
             { scheme: 'file', language: 'rmd', pattern: pattern },
           ];
           const client = await self.createClient(config, documentSelector, folder.uri.fsPath, folder, outputChannel);
-          client.start();
-          self.clients.set(key, client);
+          if (client) {
+            client.start();
+            self.clients.set(key, client);
+          }
           self.initSet.delete(key);
         }
 
@@ -205,8 +219,10 @@ export class LanguageService implements Disposable {
               { scheme: 'untitled', language: 'rmd' },
             ];
             const client = await self.createClient(config, documentSelector, os.homedir(), undefined, outputChannel);
-            client.start();
-            self.clients.set(key, client);
+            if (client) {
+              client.start();
+              self.clients.set(key, client);
+            }
             self.initSet.delete(key);
           }
           return;
@@ -222,8 +238,10 @@ export class LanguageService implements Disposable {
             ];
             const client = await self.createClient(config, documentSelector,
               path.dirname(document.uri.fsPath), undefined, outputChannel);
-            client.start();
-            self.clients.set(key, client);
+            if (client) {
+              client.start();
+              self.clients.set(key, client);
+            }
             self.initSet.delete(key);
           }
           return;

src/util.ts

@@ -310,29 +310,36 @@ export async function executeRCommand(rCommand: string, fallBack?: string, cwd?:
     const lim = '---vsc---';
     const re = new RegExp(`${lim}(.*)${lim}`, 'ms');
 
-    const args = [
-        '--silent',
-        '--slave',
-        '--no-save',
-        '--no-restore',
-    ];
-
     const rPath = await getRpath(true);
 
     const options: cp.ExecSyncOptionsWithStringEncoding = {
         cwd: cwd,
         encoding: 'utf-8'
     };
 
-    const cmd = (
-        `${rPath} ${args.join(' ')} -e "cat('${lim}')" -e "${rCommand}" -e "cat('${lim}')"`
-    );
+    const args = [
+        '--silent',
+        '--slave',
+        '--no-save',
+        '--no-restore',
+        '-e', `cat('${lim}')`,
+        '-e', rCommand,
+        '-e', `cat('${lim}')`
+    ];
 
     let ret: string = undefined;
 
     try {
-        const stdout = cp.execSync(cmd, options);
-        ret = stdout.replace(re, '$1');
+        const result = cp.spawnSync(rPath, args, options);
+        if (result.error) {
+            throw result.error;
+        }
+        const match = re.exec(result.stdout);
+        if (match.length === 2) {
+            ret = match[1];
+        } else {
+            throw new Error('Could not parse R output.');
+        }
     } catch (e) {
         if (fallBack) {
             ret = fallBack;
@@ -449,3 +456,34 @@ export function exec(command: string, args?: ReadonlyArray<string>, options?: cp
     });
     return disposable;
 }
+
+/**
+ * Check if an R package is available or not
+ *
+ * @param name the R package name that need to be checked
+ * @returns a boolean Promise
+ */
+export async function isRPkgIntalled(name: string, cwd: string, promptToInstall: boolean = false, installMsg?: string, postInstallMsg?: string): Promise<boolean> {
+    const cmd = `cat(requireNamespace('${name}', quietly=TRUE))`;
+    const rOut = await executeRCommand(cmd, 'FALSE', cwd);
+    const isInstalled = rOut === 'TRUE';
+    if (promptToInstall && !isInstalled) {
+        if (installMsg === undefined) {
+            installMsg = `R package {${name}} is not installed. Do you want to install it?`;
+        }
+        void vscode.window.showErrorMessage(installMsg, 'Yes', 'No')
+            .then(async function (select) {
+                if (select === 'Yes') {
+                    const repo = await getCranUrl('', cwd);
+                    const rPath = await getRpath(false);
+                    const args = ['--silent', '--slave', '-e', `install.packages('${name}', repos='${repo}')`];
+                    void executeAsTask('Install Package', rPath, args, true);
+                    if (postInstallMsg) {
+                        void vscode.window.showInformationMessage(postInstallMsg, 'OK');
+                    }
+                    return true;
+                }
+            });
+    }
+    return isInstalled;
+}