Disable config file watcher if a hot-reload server capability is set

src/ctx.ts

@@ -21,7 +21,7 @@ export class Ctx {
     this.config = new Config();
   }
 
-  async startServer(bin: string) {
+  async startServer(bin: string, ...features: StaticFeature[]) {
     const old = this.client;
     if (old) {
       await old.stop();
@@ -103,6 +103,7 @@ export class Ctx {
         client.registerFeature(new SemanticHighlightingFeature(client, this.context));
       }
     }
+    for (const feature of features) client.registerFeature(feature);
     this.context.subscriptions.push(services.registLanguageClient(client));
     await client.onReady();
 

src/index.ts

@@ -1,8 +1,8 @@
 import { commands, ExtensionContext, services, State, workspace } from 'coc.nvim';
-import { basename } from 'path';
 import * as cmds from './cmds';
 import { Ctx } from './ctx';
 import { FileStatus } from './file_status';
+import { ReloadFeature } from './reload';
 import * as install from './install';
 
 export async function activate(context: ExtensionContext): Promise<void> {
@@ -24,18 +24,14 @@ export async function activate(context: ExtensionContext): Promise<void> {
   }
 
   try {
-    await ctx.startServer(clangdPath);
+    await ctx.startServer(clangdPath, new ReloadFeature(ctx, () => activate(context)));
   } catch (e) {
     return;
   }
 
   const fileStatus = new FileStatus();
-  const fileWatcher = workspace.createFileSystemWatcher('**/{compile_commands.json,compile_flags.txt}');
-  fileWatcher.onDidChange((e) => reload(e.fsPath, ctx, context));
-  fileWatcher.onDidCreate((e) => reload(e.fsPath, ctx, context));
 
   context.subscriptions.push(
-    fileWatcher,
     fileStatus,
 
     commands.registerCommand('clangd.switchSourceHeader', cmds.switchSourceHeader(ctx)),
@@ -60,23 +56,3 @@ export async function activate(context: ExtensionContext): Promise<void> {
     fileStatus.onFileUpdated(status);
   });
 }
-
-async function reload(url: string, ctx: Ctx, context: ExtensionContext) {
-  const notification = ctx.config.showDBChangedNotification;
-  if (notification) {
-    const msg = `${basename(url)} has changed, clangd is reloading...`;
-    workspace.showMessage(msg);
-  }
-
-  for (const sub of ctx.subscriptions) {
-    try {
-      sub.dispose();
-    } catch (e) {
-      console.error(e);
-    }
-  }
-
-  await activate(context);
-
-  if (notification) workspace.showMessage(`clangd has reloaded`);
-}

src/reload.ts

@@ -0,0 +1,48 @@
+import { StaticFeature, workspace } from 'coc.nvim';
+import { ServerCapabilities } from 'vscode-languageserver-protocol';
+import { basename } from 'path';
+import { Ctx } from './ctx';
+
+interface ClangdClientCapabilities {
+  compilationDatabase?: { automaticReload?: boolean };
+}
+
+// FIXME: remove this feature once clangd 12 is old enough to assume that
+// server-side reload is always supported.
+export class ReloadFeature implements StaticFeature {
+  constructor(private ctx: Ctx, private activate: () => void) {}
+  initialize(caps: ServerCapabilities) {
+    // Don't restart the server if it's able to reload config files itself.
+    if ((caps as ClangdClientCapabilities).compilationDatabase?.automaticReload) {
+      return;
+    }
+
+    const fileWatcher = workspace.createFileSystemWatcher('**/{compile_commands.json,compile_flags.txt}');
+    this.ctx.subscriptions.push(
+      fileWatcher,
+      fileWatcher.onDidChange((e) => this.reload(e.fsPath)),
+      fileWatcher.onDidCreate((e) => this.reload(e.fsPath))
+    );
+  }
+
+  fillClientCapabilities() {}
+
+  async reload(url: string) {
+    const notification = this.ctx.config.showDBChangedNotification;
+    if (notification) {
+      const msg = `${basename(url)} has changed, clangd is reloading...`;
+      workspace.showMessage(msg);
+    }
+
+    for (const sub of this.ctx.subscriptions) {
+      try {
+        sub.dispose();
+      } catch (e) {
+        console.error(e);
+      }
+    }
+
+    this.activate();
+    if (notification) workspace.showMessage(`clangd has reloaded`);
+  }
+}