Support installation of clangd binaries if not found.

package.json

@@ -23,6 +23,7 @@
     "prepare": "npm-run-all clean build"
   },
   "devDependencies": {
+    "@clangd/install": "^0.1.1",
     "@types/node": "^13.13.4",
     "@types/which": "^1.3.2",
     "@typescript-eslint/eslint-plugin": "^2.30.0",
@@ -97,6 +98,11 @@
           "default": false,
           "description": "Enable semantic highlighting in clangd, requires jackguo380/vim-lsp-cxx-highlight to work"
         },
+        "clangd.checkUpdates": {
+          "type": "boolean",
+          "default": false,
+          "description": "Check for clangd language server updates on startup."
+        },
         "suggest.detailMaxLength": {
           "type": "number",
           "description": "Max length of detail that should be shown in popup menu.",
@@ -117,6 +123,14 @@
       {
         "command": "clangd.symbolInfo",
         "title": "Resolve symbol info under the cursor"
+      },
+      {
+        "command": "clangd.install",
+        "title": "Install latest clangd language server binary release"
+      },
+      {
+        "command": "clangd.update",
+        "title": "Check for updates to clangd language server"
       }
     ]
   }

src/config.ts

@@ -14,10 +14,6 @@ export class Config {
     return this.cfg.get('disableDiagnostics') as boolean;
   }
 
-  get path() {
-    return this.cfg.get('path', 'clangd');
-  }
-
   get arguments() {
     return this.cfg.get<string[]>('arguments', []);
   }

src/ctx.ts

@@ -1,7 +1,5 @@
 import { Executable, ExtensionContext, LanguageClient, LanguageClientOptions, ServerOptions, services, StaticFeature, workspace } from 'coc.nvim';
-import { existsSync } from 'fs';
 import { TextDocumentClientCapabilities } from 'vscode-languageserver-protocol';
-import which from 'which';
 import { Config } from './config';
 import { SemanticHighlightingFeature } from './semantic-highlighting';
 
@@ -22,19 +20,6 @@ export class Ctx {
     this.config = new Config();
   }
 
-  resolveBin(): string | undefined {
-    const bin = which.sync(this.config.path, { nothrow: true });
-    if (!bin) {
-      return;
-    }
-
-    if (!existsSync(bin)) {
-      return;
-    }
-
-    return bin;
-  }
-
   async startServer(bin: string) {
     const old = this.client;
     if (old) {

src/index.ts

@@ -2,28 +2,28 @@ import { commands, ExtensionContext, services, State, workspace } from 'coc.nvim
 import * as cmds from './cmds';
 import { Ctx } from './ctx';
 import { FileStatus } from './file_status';
+import * as install from './install';
 
 export async function activate(context: ExtensionContext): Promise<void> {
   const ctx = new Ctx(context);
   if (!ctx.config.enabled) {
     return;
   }
 
-  const bin = ctx.resolveBin();
-  if (!bin) {
-    workspace.showMessage(`clangd is not found, you need to install clangd first. https://clangd.llvm.org/installation.html`, 'error');
-    return;
-  }
-
   for (const service of services.getServiceStats()) {
     if (service.id.includes('clangd')) {
       workspace.showMessage(`Looks like you've configured clangd in coc-settings.json, you should remove it to use coc-clangd`, 'warning');
       return;
     }
   }
 
+  const clangdPath = await install.activate(context);
+  if (!clangdPath) {
+    return;
+  }
+
   try {
-    await ctx.startServer(bin);
+    await ctx.startServer(clangdPath);
   } catch (e) {
     return;
   }

src/install.ts

@@ -0,0 +1,63 @@
+import * as coc from 'coc.nvim';
+import * as common from '@clangd/install';
+
+class UI {
+  constructor(private context: coc.ExtensionContext, private config: coc.WorkspaceConfiguration) {}
+
+  get storagePath(): string {
+    return this.context.storagePath;
+  }
+  slow<T>(title: string, result: Promise<T>) {
+    coc.workspace.showMessage(title + '...');
+    return result;
+  }
+  error(s: string) {
+    coc.workspace.showMessage(s, 'error');
+  }
+  info(s: string) {
+    coc.workspace.showMessage(s);
+  }
+  progress<T>(title: string, _cancel: any, body: (progress: (fraction: number) => void) => Promise<T>) {
+    return this.slow(
+      title,
+      body(() => {})
+    );
+  }
+
+  async shouldReuse(release: string) {
+    coc.workspace.showMessage(`Reusing existing ${release} installation in ${this.storagePath}`);
+    return true;
+  }
+  async promptReload() {
+    await coc.commands.executeCommand('editor.action.restart');
+  }
+  showHelp(message: string, url: string) {
+    message += ` See ${url}.`;
+    coc.workspace.showMessage(message);
+  }
+  async promptUpdate(oldVersion: string, newVersion: string) {
+    const message = `clangd ${newVersion} is available (you have ${oldVersion}). :CocCommand clangd.install, or :CocSettings to disable clangd.checkUpdates.`;
+    coc.workspace.showMessage(message);
+  }
+  async promptInstall(version: string) {
+    const message = `clangd was not found on your PATH. :CocCommand clangd.install will install ${version}.`;
+    coc.workspace.showMessage(message);
+  }
+
+  get clangdPath(): string {
+    return this.config.get<string>('path')!;
+  }
+  set clangdPath(p: string) {
+    this.config.update('path', p, /*isUser=*/ true);
+  }
+}
+
+// Returns the clangd path to use, or null if clangd is not installed.
+export async function activate(context: coc.ExtensionContext): Promise<string | null> {
+  const cfg = coc.workspace.getConfiguration('clangd');
+  const ui = new UI(context, cfg);
+  context.subscriptions.push(coc.commands.registerCommand('clangd.install', async () => common.installLatest(ui)));
+  context.subscriptions.push(coc.commands.registerCommand('clangd.update', async () => common.checkUpdates(true, ui)));
+  const status = await common.prepare(ui, cfg.get<boolean>('checkUpdates', false));
+  return status.clangdPath;
+}