Support API usage when clangd is disabled or failed to initialize properly (#728)

As part of this change, uses of the non-null assertion operator (`!`) are removed.

To facilitate doing this for `ClangdContext.client`, the code is reorganized
slightly so that in the cases where this field would have been null, a
ClangdContext object is not created in the first place.

Author: HighCommander4

api/README.md

@@ -17,6 +17,11 @@ const provideHover = async (document: vscode.TextDocument, position: vscode.Posi
 
     if (clangdExtension) {
         const api = (await clangdExtension.activate()).getApi(CLANGD_API_VERSION);
+
+        // Extension may be disabled or have failed to initialize
+        if (!api.languageClient) {
+          return undefined;
+        }
 
         const textDocument = api.languageClient.code2ProtocolConverter.asTextDocumentIdentifier(document);
         const range = api.languageClient.code2ProtocolConverter.asRange(new vscode.Range(position, position));

api/vscode-clangd.d.ts

@@ -8,7 +8,7 @@ export interface ClangdApiV1 {
   // https://microsoft.github.io/language-server-protocol/specifications/specification-current
   // clangd custom requests:
   // https://clangd.llvm.org/extensions
-  languageClient: BaseLanguageClient
+  languageClient: BaseLanguageClient|undefined
 }
 
 export interface ClangdExtension {

src/api.ts

@@ -3,7 +3,7 @@ import {BaseLanguageClient} from 'vscode-languageclient';
 import {ClangdApiV1, ClangdExtension} from '../api/vscode-clangd';
 
 export class ClangdExtensionImpl implements ClangdExtension {
-  constructor(public client: BaseLanguageClient) {}
+  constructor(public client: BaseLanguageClient|undefined) {}
 
   public getApi(version: 1): ClangdApiV1;
   public getApi(version: number): unknown {

src/clangd-context.ts

@@ -58,17 +58,26 @@ class EnableEditsNearCursorFeature implements vscodelc.StaticFeature {
 
 export class ClangdContext implements vscode.Disposable {
   subscriptions: vscode.Disposable[] = [];
-  client!: ClangdLanguageClient;
+  client: ClangdLanguageClient;
 
-  async activate(globalStoragePath: string,
-                 outputChannel: vscode.OutputChannel) {
-    const clangdPath = await install.activate(this, globalStoragePath);
+  static async create(globalStoragePath: string,
+                      outputChannel: vscode.OutputChannel):
+      Promise<ClangdContext|null> {
+    const subscriptions: vscode.Disposable[] = [];
+    const clangdPath = await install.activate(subscriptions, globalStoragePath);
     if (!clangdPath)
-      return;
+      return null;
 
+    const clangdArguments = await config.get<string[]>('arguments');
+
+    return new ClangdContext(clangdPath, clangdArguments, outputChannel);
+  }
+
+  private constructor(clangdPath: string, clangdArguments: string[],
+                      outputChannel: vscode.OutputChannel) {
     const clangd: vscodelc.Executable = {
       command: clangdPath,
-      args: await config.get<string[]>('arguments'),
+      args: clangdArguments,
       options: {cwd: vscode.workspace.rootPath || process.cwd()}
     };
     const traceFile = config.get<string>('trace');
@@ -111,7 +120,8 @@ export class ClangdContext implements vscode.Disposable {
           let list = await next(document, position, context, token);
           if (!config.get<boolean>('serverCompletionRanking'))
             return list;
-          let items = (Array.isArray(list) ? list : list!.items).map(item => {
+          let items = (!list ? [] : Array.isArray(list) ? list : list.items);
+          items = items.map(item => {
             // Gets the prefix used by VSCode when doing fuzzymatch.
             let prefix = document.getText(
                 new vscode.Range((item.range as vscode.Range).start, position))

src/extension.ts

@@ -16,8 +16,7 @@ export async function activate(context: vscode.ExtensionContext):
   const outputChannel = vscode.window.createOutputChannel('clangd');
   context.subscriptions.push(outputChannel);
 
-  const clangdContext = new ClangdContext;
-  context.subscriptions.push(clangdContext);
+  let clangdContext: ClangdContext|null = null;
 
   // An empty place holder for the activate command, otherwise we'll get an
   // "command is not registered" error.
@@ -31,20 +30,27 @@ export async function activate(context: vscode.ExtensionContext):
         // stop/start cycle in this situation is pointless, and doesn't work
         // anyways because the client can't be stop()-ped when it's still in the
         // Starting state).
-        if (clangdContext.clientIsStarting()) {
+        if (clangdContext && clangdContext.clientIsStarting()) {
           return;
         }
-        await clangdContext.dispose();
-        await clangdContext.activate(context.globalStoragePath, outputChannel);
+        if (clangdContext)
+          clangdContext.dispose();
+        clangdContext = await ClangdContext.create(context.globalStoragePath,
+                                                   outputChannel);
+        if (clangdContext)
+          context.subscriptions.push(clangdContext);
         if (apiInstance) {
-          apiInstance.client = clangdContext.client;
+          apiInstance.client = clangdContext?.client;
         }
       }));
 
   let shouldCheck = false;
 
   if (vscode.workspace.getConfiguration('clangd').get<boolean>('enable')) {
-    await clangdContext.activate(context.globalStoragePath, outputChannel);
+    clangdContext =
+        await ClangdContext.create(context.globalStoragePath, outputChannel);
+    if (clangdContext)
+      context.subscriptions.push(clangdContext);
 
     shouldCheck = vscode.workspace.getConfiguration('clangd').get<boolean>(
                       'detectExtensionConflicts') ??
@@ -83,6 +89,6 @@ export async function activate(context: vscode.ExtensionContext):
     }, 5000);
   }
 
-  apiInstance = new ClangdExtensionImpl(clangdContext.client);
+  apiInstance = new ClangdExtensionImpl(clangdContext?.client);
   return apiInstance;
 }

src/install.ts

@@ -6,23 +6,23 @@ import AbortController from 'abort-controller';
 import * as path from 'path';
 import * as vscode from 'vscode';
 
-import {ClangdContext} from './clangd-context';
 import * as config from './config';
 
 // Returns the clangd path to be used, or null if clangd is not installed.
-export async function activate(
-    context: ClangdContext, globalStoragePath: string): Promise<string|null> {
-  const ui = new UI(context, globalStoragePath);
-  context.subscriptions.push(vscode.commands.registerCommand(
+export async function activate(disposables: vscode.Disposable[],
+                               globalStoragePath: string):
+    Promise<string|null> {
+  const ui = new UI(disposables, globalStoragePath);
+  disposables.push(vscode.commands.registerCommand(
       'clangd.install', async () => common.installLatest(ui)));
-  context.subscriptions.push(vscode.commands.registerCommand(
+  disposables.push(vscode.commands.registerCommand(
       'clangd.update', async () => common.checkUpdates(true, ui)));
   const status = await common.prepare(ui, config.get<boolean>('checkUpdates'));
   return status.clangdPath;
 }
 
 class UI {
-  constructor(private context: ClangdContext,
+  constructor(private disposables: vscode.Disposable[],
               private globalStoragePath: string) {}
 
   get storagePath(): string { return this.globalStoragePath; }
@@ -60,8 +60,7 @@ class UI {
   error(s: string) { vscode.window.showErrorMessage(s); }
   info(s: string) { vscode.window.showInformationMessage(s); }
   command(name: string, body: () => any) {
-    this.context.subscriptions.push(
-        vscode.commands.registerCommand(name, body));
+    this.disposables.push(vscode.commands.registerCommand(name, body));
   }
 
   async shouldReuse(release: string): Promise<boolean|undefined> {
@@ -121,7 +120,7 @@ class UI {
   }
 
   get clangdPath(): string {
-    let p = config.get<string>('path')!;
+    let p = config.get<string>('path');
     // Backwards compatibility: if it's a relative path with a slash, interpret
     // relative to project root.
     if (!path.isAbsolute(p) && p.includes(path.sep) &&