Add file watcher for compile_commands.json and other configuration files

package.json

@@ -123,6 +123,21 @@
                     "type": "boolean",
                     "default": false,
                     "description": "Check for language server updates on startup."
+                },
+                "clangd.onConfigChanged": {
+                    "type": "string",
+                    "default": "prompt",
+                    "description": "What to do when clangd configuration files are changed.",
+                    "enum": [
+                        "prompt",
+                        "restart",
+                        "ignore"
+                    ],
+                    "enumDescriptions": [
+                        "Prompt the user for restarting the server",
+                        "Automatically restart the server",
+                        "Do nothing"
+                    ]
                 }
             }
         },

src/config-file-watcher.ts

@@ -0,0 +1,73 @@
+import * as path from 'path';
+import * as vscode from 'vscode';
+
+import * as config from './config';
+
+export function activate(context: vscode.ExtensionContext) {
+  if (config.get<string>('onConfigChanged') != 'ignore') {
+    const watcher = new ConfigFileWatcher(context);
+  }
+}
+
+class ConfigFileWatcher {
+  private databaseWatcher: vscode.FileSystemWatcher = undefined;
+
+  constructor(private context: vscode.ExtensionContext) {
+    this.createFileSystemWatcher();
+    context.subscriptions.push(vscode.workspace.onDidChangeWorkspaceFolders(
+        () => { this.createFileSystemWatcher(); }));
+  }
+
+  createFileSystemWatcher() {
+    if (this.databaseWatcher)
+      this.databaseWatcher.dispose();
+    this.databaseWatcher = vscode.workspace.createFileSystemWatcher(
+        '{' +
+        vscode.workspace.workspaceFolders.map(f => f.uri.fsPath).join(',') +
+        '}/{build/compile_commands.json,compile_commands.json,compile_flags.txt,.clang-tidy}');
+    this.context.subscriptions.push(this.databaseWatcher.onDidChange(
+        this.handleConfigFilesChanged.bind(this)));
+    this.context.subscriptions.push(this.databaseWatcher.onDidCreate(
+        this.handleConfigFilesChanged.bind(this)));
+    this.context.subscriptions.push(this.databaseWatcher);
+  }
+
+  async handleConfigFilesChanged(uri: vscode.Uri) {
+    // Sometimes the tools that generate the compilation database, before
+    // writing to it, they create a new empty file or they clear the existing
+    // one, and after the compilation they write the new content. In this cases
+    // the server is not supposed to restart
+    if ((await vscode.workspace.fs.stat(uri)).size <= 0)
+      return;
+
+    switch (config.get<string>('onConfigChanged')) {
+    case 'restart':
+      vscode.commands.executeCommand('clangd.restart');
+      break;
+    case 'ignore':
+      break;
+    case 'prompt':
+    default:
+      switch (await vscode.window.showInformationMessage(
+          'Clangd configuration file at \'' + uri.fsPath +
+              '\' has been changed. Do you want to restart it?',
+          'Yes', 'Yes, always', 'No, never')) {
+      case 'Yes':
+        vscode.commands.executeCommand('clangd.restart');
+        break;
+      case 'Yes, always':
+        vscode.commands.executeCommand('clangd.restart');
+        config.update<string>('onConfigChanged', 'restart',
+                              vscode.ConfigurationTarget.Global);
+        break;
+      case 'No, never':
+        config.update<string>('onConfigChanged', 'ignore',
+                              vscode.ConfigurationTarget.Global);
+        break;
+      default:
+        break;
+      }
+      break;
+    }
+  }
+}

src/extension.ts

@@ -2,6 +2,7 @@ import * as vscode from 'vscode';
 import * as vscodelc from 'vscode-languageclient/node';
 
 import * as config from './config';
+import * as configFileWatcher from './config-file-watcher';
 import * as fileStatus from './file-status';
 import * as install from './install';
 import * as semanticHighlighting from './semantic-highlighting';
@@ -140,6 +141,7 @@ export async function activate(context: vscode.ExtensionContext) {
   console.log('Clang Language Server is now active!');
   fileStatus.activate(client, context);
   switchSourceHeader.activate(client, context);
+  configFileWatcher.activate(context);
   // An empty place holder for the activate command, otherwise we'll get an
   // "command is not registered" error.
   context.subscriptions.push(